CPP magnetic sensing element

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to current-perpendicular-to-the-plane (CPP) magnetic sensing elements and, more particularly, to a magnetic sensing element in which read sensitivity and read output can be improved even when the track is narrowed.

[0003] 2. Description of the Related Art

[0004]FIG. 7 is a partial sectional view of a conventional CIP magnetic sensing element, viewed from the surface facing a recording medium. Herein, CIP stands for current-in-the-plane, and in the CIP magnetic sensing element, a sensing current flows parallel to the planes of a multilayer film which is located in the center of the magnetic sensing element.

[0005] Referring to FIG. 7, the magnetic sensing element includes a lower shielding layer <b>1</b> composed of Permalloy (NiFe alloy) or the like and a lower gap layer <b>2</b> composed of Al₂O₃or the like disposed thereon.

[0006] On the lower gap layer <b>2</b>, an underlayer <b>3</b>, a seed layer <b>4</b>, a first antiferromagnetic layer <b>5</b>, a pinned magnetic layer <b>6</b>, a first nonmagnetic layer <b>7</b>, a free magnetic layer <b>8</b>, a second nonmagnetic layer <b>9</b>, and a second antiferromagnetic layer <b>10</b> are deposited, and the laminate from the underlayer <b>3</b> to the second antiferromagnetic layer <b>10</b> is hereinafter referred to as a multilayer film <b>11</b>.

[0007] The first antiferromagnetic layer <b>5</b> is composed of an antiferromagnetic material, such as a PtMn alloy, each of the pinned magnetic layer <b>6</b> and the free magnetic layer <b>8</b> is composed of a ferromagnetic material, such as a NiFe alloy, and the first nonmagnetic layer <b>7</b> is composed of a nonmagnetic conductive material, such as Cu.

[0008] End faces <b>11</b><i>a </i>at both sides in the track width direction (in the X direction) of the multilayer film <b>11</b> are formed by etching. Although the end faces <b>11</b><i>a </i>extend perpendicular to a plane (X-Y plane) parallel to the planes of the multilayer film <b>11</b> in the drawing, the end faces <b>11</b><i>a </i>are actually inclined planes.

[0009] A track width Tw is determined by the width in the track width direction (in the X direction) of the free magnetic layer <b>8</b>. As the recording density is increased, the track width Tw is considerably decreased.

[0010] Electrode layers <b>12</b> are formed on the end faces <b>11</b><i>a </i>of the multilayer film <b>11</b>. As shown in FIG. 7, an upper gap layer <b>13</b> composed of Al₂O₃or the like extends over the multilayer film <b>11</b> and the electrode layers <b>12</b>, and an upper shielding layer <b>14</b> composed of Permalloy or the like is disposed on the upper gap layer <b>13</b>.

[0011] In the conventional magnetic sensing element shown in FIG. 7, the second antiferromagnetic layer <b>10</b> is formed on the free magnetic layer <b>8</b> with the second nonmagnetic layer <b>9</b> therebetween. In such a structure, unidirectional interlayer exchange coupling occurs between the second antiferromagnetic layer <b>10</b> and the free magnetic layer <b>8</b>, and a unidirectional longitudinal bias magnetic field is applied to the free magnetic layer <b>8</b>.

[0012] If the interlayer exchange coupling magnetic field is too strong, the sensitivity of the free magnetic layer <b>8</b> to an external magnetic field is weakened. The magnitude of the interlayer exchange coupling can be controlled by changing the thickness of the second nonmagnetic layer <b>9</b>.

[0013] As track narrowing is accelerated, the means for applying the longitudinal bias magnetic field shown in FIG. 7 is considered as one of the optimum means.

[0014] As described above, the magnetic sensing element shown in FIG. 7 is a CIP magnetic sensing element in which a sensing current flows parallel to the planes of the multilayer film <b>11</b>. Recently, attention is being given to a current-perpendicular-to-the-plane (CPP) magnetic sensing element in which read output can be increased even if the element is miniaturized.

[0015]FIG. 8 is a longitudinal sectional view of a CPP magnetic sensing element using the means for applying the longitudinal bias magnetic field described with reference to FIG. 7, viewed from the surface facing a recording medium.

[0016] A multilayer film <b>11</b> shown in FIG. 8 has the same structure as that shown in FIG. 7 except that electrode layers <b>16</b> and <b>15</b> are provided on the upper and lower faces in the thickness direction (in the Z direction) of the multilayer film <b>11</b>, respectively, and insulating layers <b>17</b> composed of Al₂O₃or the like are formed at both sides in the track width direction (in the X direction) of the multilayer film <b>11</b>.

[0017] In the CPP magnetic sensing element, a sensing current flows parallel to the thickness direction of the multilayer film <b>11</b>. Consequently, the electrode layers <b>16</b> and <b>15</b> are provided on the upper and lower faces in the thickness direction of the multilayer film <b>11</b>, respectively.

[0018] In the CPP magnetic sensing element, in order to effectively improve the read output, the product (ΔR×A) of a change in resistance ΔR and an area A of the plane (X-Y plane) parallel to the planes of the multilayer film <b>11</b> must be increased.

[0019] An increase in the thickness hl of the free magnetic layer <b>8</b> has been considered to be one method for gaining the product (ΔR×A) under the situation of miniaturization of the element with track narrowing.

[0020] However, if the thickness hl of the free magnetic layer <b>8</b> is increased, the demagnetizing field of the free magnetic layer <b>8</b> is increased, resulting in a degradation in the read sensitivity η.

[0021] An attempt has been made to control the magnetization of the free magnetic layer <b>8</b> by strengthening the interlayer exchange coupling generated between the free magnetic layer <b>8</b> and the second antiferromagnetic layer <b>10</b> so as to counteract the demagnetizing field.

[0022] The strength of the interlayer exchange coupling can be controlled by changing the thickness of the second nonmagnetic layer <b>9</b> interposed between the free magnetic layer <b>8</b> and the second antiferromagnetic layer <b>10</b>. However, if the interlayer exchange coupling is strengthened, although the influence of the demagnetizing field may be weakened, since a strong unidirectional longitudinal bias magnetic field is applied to the free magnetic layer <b>8</b>, the magnetic reversal of the free magnetic layer <b>8</b> becomes insensitive to an external magnetic field or does not occur. As a result, it is not possible to fabricate a magnetic sensing element with excellent read sensitivity.

[0023] That is, in any case, in the conventional CPP magnetic sensing element having a structure including the means for applying the longitudinal bias magnetic field shown in FIG. 7, it is not possible to improve read sensitivity η and read output simultaneously.

SUMMARY OF THE INVENTION

[0024] It is an object of the present invention to provide a magnetic sensing element in which both read sensitivity η and read output are improved by the improved structure of the free magnetic layer, and which is thereby suitable for miniaturization of the element.

[0025] In accordance with the present invention, a magnetic sensing element includes a multilayer film including a first antiferromagnetic layer; a pinned magnetic layer in contact with the first antiferromagnetic layer; a first nonmagnetic layer in contact with the pinned magnetic layer; a free magnetic layer in contact with the first nonmagnetic layer, the free magnetic layer including a second free magnetic sublayer in contact with the first nonmagnetic layer, a nonmagnetic intermediate sublayer, and a first free magnetic sublayer; a second nonmagnetic layer in contact with the first free magnetic sublayer; and a second antiferromagnetic layer in contact with the second nonmagnetic layer. A current flows perpendicular to the plane of each layer in the multilayer film.

[0026] In the present invention, the free magnetic layer has a laminated ferrimagnetic structure including the first free magnetic sublayer, the second free magnetic sublayer, and the nonmagnetic intermediate sublayer disposed therebetween.

[0027] The magnetization directions of the first free magnetic sublayer and the second free magnetic sublayer are antiparallel to each other. In order to achieve an antiparallel state properly between the magnetization directions of the first free magnetic sublayer and the second free magnetic sublayer, the first free magnetic sublayer and the second free magnetic sublayer are formed so as to have different magnetic moments per unit area. The magnetic moment per unit area is determined by the product of the saturation magnetization (Ms) and the film thickness (t).

[0028] Since both the first free magnetic sublayer and the second free magnetic sublayer are composed of ferromagnetic materials, the physical thickness of the free magnetic layer corresponds to the total thickness of the first free magnetic sublayer and the second free magnetic sublayer. Since the physical thickness of the free magnetic layer can be increased in such a manner, the product of a change in resistance ΔR and an area A can be increased even if the element is miniaturized.

[0029] On the other hand, by forming the laminated ferrimagnetic structure in which the magnetization directions of the first free magnetic sublayer and the second free magnetic sublayer are antiparallel to each other, the demagnetizing field of the free magnetic layer is weakened because of a decrease in the magnetic thickness. Consequently, interlayer exchange coupling can be generated between the second antiferromagnetic layer and the free magnetic layer at an appropriate magnitude, and read sensitivity η can be improved.

[0030] That is, in the present invention, it is possible to fabricate a magnetic sensing element in which the product of a change in resistance ΔR and an area A can be increased and the read output can be improved compared to the conventional CPP magnetic sensing element shown in FIG. 8, and which has excellent read characteristics, such as satisfactory sensitivity and small hysteresis.

[0031] In the present invention, preferably, the second nonmagnetic layer is composed of at least one element selected from the group consisting of Cu, Au, Ag, and Ru. When the second nonmagnetic layer is composed of Cu, the thickness of the second nonmagnetic layer is preferably 0.5 to 8 Å.

[0032] The thickness of the second nonmagnetic layer is extremely important in the present invention. The reason for this is that the magnitude of the interlayer exchange coupling generated between the first free magnetic sublayer and the second antiferromagnetic layer is greatly influenced by the thickness of the second nonmagnetic layer. As the thickness of the second nonmagnetic layer is decreased, the interlayer exchange coupling can be strengthened. As the thickness of the second nonmagnetic layer is increased, the interlayer exchange coupling can be weakened.

[0033] The interlayer exchange coupling must have a proper magnitude. Specifically, the magnitude of the interlayer exchange coupling is preferably approximately 795 to 15,900 A/m (approximately 10 to 200 Oe). By setting the thickness of the second nonmagnetic layer as described above, it is possible to generate interlayer exchange coupling in this level. By setting the magnitude of the interlayer exchange coupling at approximately 795 to 15,900 A/m (approximately 10 to 200 Oe), alignment in a single domain state and magnetic reversal to an external magnetic field of the free magnetic layer can be satisfactory performed, and it is possible to fabricate a magnetic sensing element with excellent read characteristics.

[0034] In the present invention, preferably, the first free magnetic sublayer includes a magnetic region composed of a CoFe alloy. More preferably, the region composed of the CoFe alloy is located at the interface with the second nonmagnetic layer and has a predetermined thickness.

[0035] If the first free magnetic sublayer includes a magnetic region composed of a CoFe alloy, and in particular, if the magnetic region is located in the vicinity of the interface with the second nonmagnetic layer, the change in the magnitude of the interlayer exchange coupling generated between the first free magnetic sublayer and the second antiferromagnetic layer can be moderated with respect to the change in the thickness of the second nonmagnetic layer, for example, compared to a case in which the first free magnetic sublayer includes a magnetic region composed of a NiFe alloy in the vicinity of the interface with the second nonmagnetic layer. Therefore, the thickness of the second nonmagnetic layer can be set in a relatively wide range, and the magnetization of the free magnetic layer can be easily controlled. In particular, since the second nonmagnetic layer must have an extremely small thickness of several angstroms, it is extremely meaningful to future practical use of the CPP magnetic sensing element that the setting range of the thickness of the second nonmagnetic layer can be widened.

[0036] The magnetic region composed of the CoFe alloy also acts as a diffusion-preventing layer which prevents the diffusion of elements at the interface with the second nonmagnetic layer.

[0037] In the present invention, the magnetic region composed of the CoFe alloy may be located at the interface with the nonmagnetic intermediate sublayer and have a predetermined thickness.

[0038] In the present invention, preferably, the total thickness of the first free magnetic sublayer and the second free magnetic sublayer is 70 to 250 Å, and the difference between the thickness of the first free magnetic sublayer and the thickness of the second free magnetic sublayer is 5 to 70 Å.

[0039] In the present invention, preferably, the second antiferromagnetic layer is composed of an antiferromagnetic material containing X and Mn, wherein X is at least one element selected from the group consisting of Pt, Pd, Ir, Rh, Ru, and Os.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIG. 1 is a partial sectional view of a CPP magnetic sensing element in a first embodiment of the present invention, viewed from the surface facing a recording medium;

[0041]FIG. 2 is a partial sectional view of a CPP magnetic sensing element in a second embodiment of the present invention, viewed from the surface facing a recording medium;

[0042]FIG. 3 is a partial sectional view of a CPP magnetic sensing element in a third embodiment of the present invention, viewed from the surface facing a recording medium;

[0043]FIG. 4 is a sectional view which shows a step in a method for fabricating the magnetic sensing element shown in FIG. 2;

[0044]FIG. 5 is a sectional view which shows a step subsequent to the step shown in FIG. 4;

[0045]FIG. 6 is a sectional view which shows a step subsequent to the step shown in FIG. 5;

[0046]FIG. 7 is a partial sectional view of a conventional CIP magnetic sensing element, viewed from the surface facing a recording medium; and

[0047]FIG. 8 is a partial sectional view of a conventional CPP magnetic sensing element, viewed from the surface facing a recording medium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048]FIG. 1 is a partial sectional view which shows an overall structure of a magnetic sensing element in a first embodiment of the present invention, viewed from the surface facing a recording medium. In FIG. 1, only the central part of the element is shown.

[0049] The magnetic sensing element shown in FIG. 1 reads the signals written in the recording medium. Although not shown in the drawing, an inductive head for writing may be deposited on the magnetic sensing element.

[0050] The magnetic sensing element is formed on the trailing end of a slider, for example, composed of alumina-titanium carbide (Al₂O₃-TiC). The slider is connected to an elastically deformable support composed of a stainless steel or the like at a surface opposite to the surface facing the recording medium, and thus a magnetic head device is produced.

[0051] A lower shielding layer <b>20</b> is composed of a magnetic material, such as a NiFe alloy, and also acts as a lower electrode in this embodiment.

[0052] An underlayer <b>21</b> composed of a nonmagnetic material is disposed on the lower shielding layer <b>20</b>. The underlayer <b>21</b> also acts as a lower gap layer. Preferably, the underlayer <b>21</b> is composed of at least one element selected from the group consisting of Ta, Hf, Nb, Zr, Ti, Mo, and W. The underlayer <b>21</b>, for example, has a thickness of approximately 50 Å or less.

[0053] A seed layer <b>22</b> is disposed on the underlayer <b>21</b>. By forming the seed layer <b>22</b>, the grain diameters, in a direction parallel to the planes, of the individual layers formed on the seed layer <b>22</b> can be increased, and current-carrying reliability, such as electromigration resistance, and the rate of change in resistance (AR/R) can be more appropriately improved.

[0054] The seed layer <b>22</b> is composed of a NiFe alloy, a NiFeCr alloy, or Cr. The seed layer <b>22</b> may be omitted.

[0055] A first antiferromagnetic layer <b>23</b> is disposed on the seed layer <b>22</b>. Preferably, the first antiferromagnetic layer <b>23</b> is composed of an antiferromagnetic material containing X and Mn, wherein X is at least one element selected from the group consisting of Pt, Pd, Ir, Rh, Ru, and Os. Alternatively, preferably, the first antiferromagnetic layer <b>23</b> is composed of an antiferromagnetic material containing, X, X′, and Mn, wherein X′ is at least one element selected from the group consisting of Ne, Ar, Kr, Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, Cd, Sn, Hf, Ta, W, Re, Au, Pb, and rare-earth elements.

[0056] Such antiferromagnetic materials exhibit superior corrosion resistance and high blocking temperatures and can generate large exchange anisotropic magnetic fields at the interface with a pinned magnetic layer <b>24</b> which will be described below. Preferably, the first antiferromagnetic layer <b>23</b> has a thickness of 80 to 300 Å.

[0057] The pinned magnetic layer <b>24</b> is disposed on the first antiferromagnetic layer <b>23</b>. The pinned magnetic layer <b>24</b> is composed of a ferromagnetic material, such as a CoFe alloy, a NiFe alloy, a CoFeNi alloy, or Co. In order to strengthen the exchange coupling magnetic field generated between the first antiferromagnetic layer <b>23</b> and the pinned magnetic layer <b>24</b>, preferably, the pinned magnetic layer <b>24</b> is composed of a CoFe alloy. Although the pinned magnetic layer <b>24</b> shown in FIG. 1 has a single-layer structure, the structure of the pinned magnetic layer <b>24</b> is not limited thereto. Other structures for the pinned magnetic layer <b>24</b> will be described later.

[0058] As described above, an exchange coupling magnetic field is generated between the first antiferromagnetic layer <b>23</b> and the pinned magnetic layer <b>24</b> by annealing in a magnetic field, and the magnetization direction of the pinned magnetic layer <b>24</b> is pinned, for example, in the height direction (in the Y direction).

[0059] As shown in FIG. 1, a first nonmagnetic layer <b>25</b> is disposed on the pinned magnetic layer <b>24</b>. The first nonmagnetic layer <b>25</b> is composed of a conductive material having a low electrical resistance, such as Cu. The first nonmagnetic layer <b>25</b> has a thickness of, for example, approximately 25 Å.

[0060] Additionally, the first nonmagnetic layer <b>25</b> may be composed of an insulating material, such as Al₂O₃or SiO₂. Such a magnetic sensing element is referred to as a tunneling magnetoresistive element.

[0061] In the tunneling magnetoresistive element, resistance change is caused by the tunneling effect. When the magnetization directions of the pinned magnetic layer <b>24</b> and a free magnetic layer <b>26</b> are antiparallel to each other, the tunneling current least easily flows through the first nonmagnetic layer <b>25</b>, resulting in the maximum resistance. When the magnetization directions of the pinned magnetic layer <b>24</b> and the free magnetic layer <b>26</b> are parallel to each other, the tunneling current most easily flows through the first nonmagnetic layer <b>25</b>, resulting in the minimum resistance.

[0062] Using this principle, the varying electrical resistance due to a change in the magnetization of the free magnetic layer <b>26</b> under the influence of an external magnetic field is detected as a change in voltage, and the leakage magnetic field from the recording medium is thereby detected.

[0063] The free magnetic layer <b>26</b> is disposed on the first nonmagnetic layer <b>25</b>. In this embodiment, the free magnetic layer <b>26</b> has a quadruple-layer structure. A second free magnetic sublayer <b>31</b> in contact with the first nonmagnetic layer <b>25</b> is divided into magnetic regions <b>27</b> and <b>28</b>. A first free magnetic sublayer <b>30</b> is disposed on the second free magnetic sublayer <b>31</b> with a nonmagnetic intermediate sublayer <b>29</b> therebetween. In this embodiment, for example, the magnetic region <b>27</b> in contact with the first nonmagnetic layer <b>25</b> is composed of a CoFe alloy, and the magnetic region <b>28</b> is composed of a NiFe alloy.

[0064] The nonmagnetic intermediate sublayer <b>29</b> is preferably composed of at least one nonmagnetic conductive material selected from the group consisting of Ru, Rh, Ir, Os, Cr, Re, and Cu.

[0065] In this embodiment, for example, the first free magnetic sublayer <b>30</b> has a single-layer structure composed of a CoFe alloy.

[0066] As shown in FIG. 1, a second nonmagnetic layer <b>32</b> is disposed on the upper surface, i.e., a surface opposite to the surface in contact with the first nonmagnetic layer <b>25</b>, of the free magnetic layer <b>26</b>, and a second antiferromagnetic layer <b>33</b> is disposed on the second nonmagnetic layer <b>32</b>. In the embodiment shown in FIG. 1, a protective layer <b>34</b> composed of Ta or the like is disposed on the second antiferromagnetic layer <b>33</b>. The protective layer <b>34</b> may be composed of at least one element selected from the group consisting of Ta, Hf, Nb, Zr, Ti, Mo, and W. In this embodiment, the protective layer <b>34</b> also acts as an upper gap layer.

[0067] In the embodiment shown in FIG. 1, a laminate from the underlayer <b>21</b> to the protective layer <b>34</b> formed on the lower shielding layer <b>20</b> is referred to as a multilayer film <b>35</b>. Although end faces <b>35</b><i>a </i>at both sides in the track width direction (in the X direction) of the multilayer film <b>35</b> extend perpendicular to a plane (X-Y plane) parallel to the planes of the multilayer film <b>35</b> in the drawing, the end faces <b>35</b><i>a </i>are actually inclined planes or curved planes, that is, the width in the track width direction of the multilayer film <b>35</b> gradually decreases in the thickness direction. The end faces <b>35</b><i>a </i>are formed by etching. A track width Tw is determined by the width in the track width direction of the free magnetic layer <b>26</b>. The track width Tw is preferably 0.1 μm or less.

[0068] In the embodiment shown in FIG. 1, insulating layers <b>36</b> are placed at both end faces <b>35</b><i>a </i>of the multilayer film <b>35</b>. The insulating layers <b>36</b> are placed on both ends of the lower shielding layer <b>20</b> which extends in the track width direction from the end faces <b>35</b><i>a </i>of the multilayer film <b>35</b>. The insulating layers <b>36</b> are in contact with the end faces <b>35</b><i>a</i>. A specular film composed of an insulating oxide may be formed between each insulating layer <b>36</b> and each end face <b>35</b><i>a</i>. The formation of the specular films extends the mean free path of conduction electrons, resulting in an improvement in the rate of change in resistance. In particular, as the track is narrowed, the formation of the specular films on both end faces <b>35</b><i>a </i>of the multilayer film <b>35</b> becomes one of the optimum structures. The insulating layers <b>36</b> are composed of an insulating material, such as Al₂O₃or SiO₂.

[0069] In the embodiment shown in FIG. 1, an upper shielding layer <b>37</b> extends over the multilayer film <b>35</b> and the insulating layers <b>36</b>. The upper shielding layer <b>37</b> is composed of a soft magnetic material, such as a NiFe alloy, and also acts as an upper electrode.

[0070] In the embodiment shown in FIG. 1, since the lower shielding layer <b>20</b> and the upper shielding layer <b>37</b> also act as the electrodes, a gap length G1 can be determined by the total thickness of the laminate including the underlayer <b>21</b> to the protective layer <b>34</b>, and the gap length G1 can be decreased.

[0071] The magnetic sensing element shown in FIG. 1 is a current-perpendicular-to-the-plane (CPP) type, in which the upper and lower shielding layers <b>37</b> and <b>20</b> which also act as the electrodes are disposed on the upper and lower surfaces of the multilayer film <b>35</b>, respectively, and a current flows between the upper and lower shielding layers <b>37</b> and <b>20</b> through the multilayer film <b>35</b> in the thickness direction (in the Z direction). Since the end faces <b>35</b><i>a </i>of the multilayer film <b>35</b> are surrounded by the insulating layers <b>36</b>, the current flows within the multilayer film <b>35</b> properly, thus improving the read output.

[0072] In the magnetic sensing element, the recording medium, such as a hard disk, travels in the Z direction. When a leakage magnetic field is applied in the Y direction from the recording medium, the magnetization direction of the second free magnetic sublayer <b>31</b> is changed from the X direction to the Y direction. Electrical resistance changes due to the relationship between the varying magnetization direction of the second free magnetic sublayer <b>31</b> and the pinned magnetization direction of the pinned magnetic layer <b>24</b>, which is referred to as the magnetoresistance effect, and the leakage magnetic field from the magnetic recording medium is detected by a voltage change based on the change in the electrical resistance.

[0073] The features of the magnetic sensing element shown in FIG. 1 will be described below. In the embodiment shown in FIG. 1, the free magnetic layer <b>26</b> has a triple-layer structure including the first free magnetic sublayer <b>30</b>, the second free magnetic sublayer <b>31</b>, and the nonmagnetic intermediate sublayer <b>29</b> disposed therebetween. Such a structure is referred to as a laminated ferrimagnetic structure. Antiferromagnetic interlayer exchange coupling (RKKY exchange interaction) is produced between the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b>. Consequently, the magnetization directions of the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> are antiparallel to each other. For example, if the first free magnetic sublayer <b>30</b> is magnetized parallel to the track width direction rightward, the second free magnetic sublayer <b>31</b> is magnetized leftward in the drawing.

[0074] As shown in FIG. 1, the second antiferromagnetic layer <b>33</b> is disposed on the first free magnetic sublayer <b>30</b> with the second nonmagnetic layer <b>32</b> therebetween. Unidirectional interlayer exchange coupling is produced between the first free magnetic sublayer <b>30</b> and the second antiferromagnetic layer <b>33</b>, and the first free magnetic sublayer <b>30</b> is aligned in a single domain state, for example, rightward.

[0075] However, the unidirectional interlayer exchange coupling must be relatively weak. If the interlayer exchange coupling is strong, the magnetization of the first free magnetic sublayer <b>30</b> is easily pinned rightward. In such a case, the magnetization of the second free magnetic sublayer which actually contributes to the magnetoresistance effect is easily pinned leftward due to the antiferromagnetic interlayer exchange coupling generated between the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b>, the magnetization of the second free magnetic sublayer <b>31</b> is not easily rotated in response to an external magnetic field, resulting in a decrease in output sensitivity.

[0076] The embodiment shown in FIG. 1 is characterized in that the free magnetic layer <b>26</b> has the laminated ferrimagnetic structure and that the magnetization of the free magnetic layer <b>26</b> is controlled by the second antiferromagnetic layer <b>33</b> with the second nonmagnetic layer <b>32</b> therebetween.

[0077] Since the free magnetic layer <b>26</b> has the laminated ferrimagnetic structure, the physical thickness of the free magnetic layer <b>26</b> corresponds to the total thickness of a thickness t3 of the first free magnetic sublayer <b>30</b> and a thickness t2 of the second free magnetic sublayer <b>31</b>. Consequently, the physical thickness of the free magnetic layer <b>26</b> can be increased, and even if the element is miniaturized, the product of a change in resistance ΔR and an area A of the plane (X-Y plane) parallel to the planes of the multilayer film <b>35</b> can be increased.

[0078] On the other hand, the demagnetizing field of the free magnetic layer <b>26</b> is weakened because the magnetic thickness is decreased by the laminated ferrimagnetic structure in which the magnetization directions of the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> are antiparallel to each other. Consequently, the unidirectional interlayer exchange coupling magnetic field generated between the second antiferromagnetic layer <b>33</b> and the free magnetic layer <b>26</b> can be applied continuously to the free magnetic layer <b>26</b> in an appropriate magnitude, resulting in an improvement in the read sensitivity η.

[0079] As described above, in the present invention, it is possible to improve read sensitivity η and the read output simultaneously, and it is possible to fabricate a magnetic sensing element which is suitable for the miniaturization of the element with the future increase in the recording density.

[0080] The second nonmagnetic layer <b>32</b> is preferably composed of Cu, Au, Ag, or Ru.

[0081] Unidirectional interlayer exchange coupling is produced between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>30</b>. The interlayer exchange coupling must be relatively weak. If the interlayer exchange coupling is strong, the first free magnetic sublayer <b>30</b> is strongly magnetized, and therefore, the second free magnetic sublayer <b>31</b>, to which the antiferromagnetic interlayer exchange coupling with the first free magnetic sublayer <b>30</b> is applied, is also strongly magnetized, resulting in a degradation in the read sensitivity to an external magnetic field.

[0082] In order to set the unidirectional interlayer exchange coupling between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>30</b> relatively weak, the second nonmagnetic layer <b>32</b> must be composed of Cu, Au, Ag, or Ru, and the thickness of the second nonmagnetic layer <b>32</b> must be adjusted.

[0083] In the present invention, when the second nonmagnetic layer <b>32</b> is composed of Cu, the thickness of the second nonmagnetic layer <b>32</b> is preferably 0.5 to 8 Å.

[0084] By setting the thickness of the second nonmagnetic layer <b>32</b> in the range described above, the magnitude of the unidirectional interlayer exchange coupling between the first free magnetic sublayer <b>30</b> and the second antiferromagnetic layer <b>33</b> can be set at approximately 795 to 15,900 A/m (approximately 10 to 200 Oe), and thereby it is possible to prevent the first free magnetic sublayer <b>30</b> from being pinned by strong interlayer exchange coupling.

[0085] Next, the magnetic moments per unit area of the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> will be described below.

[0086] In the embodiment shown in FIG. 1, the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> have different magnetic moments per unit area. The magnetic moment per unit area is defined as the product of the saturation magnetization (Ms) and the thickness (t).

[0087] By setting the magnetic moments per unit area of the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> to be different from each other, the magnetization directions of the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> can be antiparallel to each other appropriately.

[0088] Preferably, the total thickness of the thickness t3 of the first free magnetic sublayer <b>30</b> and the thickness t2 of the second free magnetic sublayer <b>31</b> is 70 to 250 Å. By forming the free magnetic layer <b>26</b> at such a thickness, the product of the change in resistance ΔR and the area A can be effectively increased.

[0089] Preferably, the difference between the thickness t3 of the first free magnetic sublayer <b>30</b> and the thickness t2 of the second free magnetic sublayer <b>31</b> is 5 to 70 Å. By setting the difference in the thickness between the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> in the range described above, the demagnetizing field of the free magnetic layer <b>26</b> can be effectively weakened, and in particular, the demagnetizing field can be brought close to zero.

[0090] Preferably, the difference between the magnetic moment per unit area of the first free magnetic sublayer <b>30</b> and the magnetic moment per unit area of the second free magnetic sublayer <b>31</b> is 0.04 memu/cm²(0.5 T.nm) to 0.56 memu/cm²(7.06 T.nm). By setting the difference in the magnetic moment per unit area between the first free magnetic sublayer <b>30</b> and the second free magnetic sublayer <b>31</b> in the range described above, the demagnetizing field of the free magnetic layer <b>26</b> can be effectively weakened, and in particular, the demagnetizing field can be brought close to zero.

[0091] The material for the free magnetic layer <b>26</b> will now be described. In the embodiment shown in FIG. 1, the second free magnetic sublayer <b>31</b> has a double-layer structure. As described above, for example, the magnetic region <b>27</b> is a CoFe alloy layer and the magnetic region <b>28</b> is a NiFe alloy layer.

[0092] Since the magnetic region <b>27</b> is the CoFe alloy layer, i.e., the magnetic region composed of the CoFe alloy, is located in the vicinity of the interface with the first nonmagnetic layer <b>25</b>, it is possible to appropriately prevent Ni of the magnetic region <b>28</b> from diffusing into the first nonmagnetic layer <b>25</b>.

[0093] The first free magnetic sublayer <b>30</b> is composed of a CoFe alloy. By forming the first free magnetic sublayer <b>30</b> using a CoFe alloy, the variation in the magnitude of the unidirectional interlayer exchange coupling generated between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>30</b> can be moderated compared to a case in which the first free magnetic sublayer <b>30</b> is composed of a NiFe alloy.

[0094] As the thickness of the second nonmagnetic layer <b>32</b> is increased, the magnitude of the unidirectional interlayer exchange coupling between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>30</b> is decreased. As the thickness of the second nonmagnetic layer <b>32</b> is decreased, the magnitude of the interlayer exchange coupling is increased.

[0095] However, the variation in the magnitude of the interlayer exchange coupling becomes extremely large if the first free magnetic sublayer <b>30</b> is composed of a NiFe alloy. Therefore, in order to obtain required interlayer exchange coupling, the thickness of the second nonmagnetic layer <b>32</b> and the thickness of the free magnetic sublayer <b>30</b> must be set extremely strictly, resulting in a decrease in the production yield. In particular, the thickness of the second nonmagnetic layer <b>32</b> must be set at an extremely small value of several angstroms, and if the allowance of the proper thickness is small, it is not easy to form the second nonmagnetic layer <b>32</b> at a predetermined thickness.

[0096] In contrast, if the first free magnetic sublayer <b>30</b> is composed of a CoFe alloy, since the variation in the magnitude of the interlayer exchange coupling becomes relatively moderate, the allowance of the proper thicknesses for the second nonmagnetic layer <b>32</b> and the first free magnetic sublayer <b>30</b> become larger compared to a case in which the first free magnetic sublayer <b>30</b> is composed of a NiFe alloy. Consequently, the second nonmagnetic layer <b>32</b> and the first free magnetic sublayer <b>30</b> are easily formed at thicknesses within the predetermined ranges, and interlayer exchange coupling with a predetermined magnitude is easily obtained.

[0097] The materials for the magnetic layers <b>27</b>, <b>28</b>, and <b>30</b> described above are taken as an example, and the present invention is not limited thereto. For example, the magnetic layer <b>27</b> may be composed of Co. The magnetic layer <b>28</b> may be composed of a CoFeNi alloy. The first free magnetic sublayer <b>30</b> may be composed of a CoFeNi alloy.

[0098] The second antiferromagnetic layer <b>33</b> will now be described. The second antiferromagnetic layer <b>33</b> is preferably composed of an antiferromagnetic material containing X and Mn, wherein X is at least one element selected from the group consisting of Pt, Pd, Ir, Rh, Ru, and Os. For example, the second antiferromagnetic layer <b>33</b> is composed of a PtMn alloy.

[0099] The magnitude of the unidirectional interlayer exchange coupling between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>30</b> is also influenced by the material for the second antiferromagnetic layer <b>33</b>. The interlayer exchange coupling magnetic field must have a proper magnitude. By forming the second antiferromagnetic layer <b>33</b> using a PtMn alloy or the like, the variation in the magnitude of the interlayer exchange coupling in response to the variation in the thickness of the second nonmagnetic layer <b>32</b> can be moderated, and interlayer exchange coupling with a predetermined magnitude is easily obtained. The antiferromagnetic material containing X and Mn, wherein X is at least one element selected from the group consisting of Pt, Pd, Ir, Rh, Ru, and Os, exhibits excellent corrosion resistance, which is also desirable.

[0100] The thickness of the second antiferromagnetic layer <b>33</b> is preferably 70 to 300 Å. By setting the thickness of the second antiferromagnetic layer <b>33</b> within the range described above, interlayer exchange coupling with a predetermined magnitude is easily obtained. Additionally, the second antiferromagnetic layer <b>33</b> may be composed of an antiferromagnetic material containing, X, X′, and Mn, wherein X′ is at least one element selected from the group consisting of Ne, Ar, Kr, Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, Cd, Sn, Hf, Ta, W, Re, Au, Pb, and rare-earth elements.

[0101]FIG. 2 is a partial sectional view of a magnetic sensing element in a second embodiment of the present invention, viewed from the surface facing a recording medium. The same reference numerals as those in FIG. 1 are used in FIG. 2 for the same layers.

[0102] In the embodiment shown in FIG. 2, a free magnetic layer <b>26</b> also has a laminated ferrimagnetic structure, and a second nonmagnetic layer <b>32</b> and a second antiferromagnetic layer <b>33</b> are deposited on a surface of a first free magnetic sublayer <b>53</b> opposite to the surface in contact with a nonmagnetic intermediate sublayer <b>49</b>.

[0103] Consequently, unidirectional interlayer exchange coupling is produced between the first free magnetic sublayer <b>53</b> and the second antiferromagnetic layer <b>33</b>, and the first free magnetic sublayer <b>53</b> is aligned in a single domain state in the track width direction. The free magnetic layer <b>26</b> has the laminated ferrimagnetic structure and the physical thickness of the free magnetic layer <b>26</b> corresponds to the total thickness of the first free magnetic sublayer <b>53</b> and a second free magnetic sublayer <b>48</b>. Since the physical thickness is increased, the product of the change in resistance ΔR and the area A can be improved and the read output can be improved. Since the magnetic thickness is decreased due to the laminated ferrimagnetic structure, the demagnetizing field of the free magnetic layer <b>26</b> is decreased, and a continuous bias with a proper magnitude can be stably applied from the second antiferromagnetic layer <b>33</b> to the first free magnetic sublayer <b>53</b>. Therefore, it is possible to fabricate a magnetic sensing element with satisfactory read sensitivity η.

[0104] In the embodiment shown in FIG. 2, a pinned magnetic layer <b>24</b> has a laminated ferrimagnetic structure like the free magnetic layer <b>26</b>. In the embodiment shown in FIG. 2, the pinned magnetic layer <b>24</b> has a quadruple-layer structure.

[0105] A first pinned magnetic sublayer <b>40</b> is, for example, composed of a CoFe alloy. A second pinned magnetic sublayer <b>44</b> is disposed on the first pinned magnetic sublayer <b>40</b> with a nonmagnetic intermediate sublayer <b>41</b> therebetween. In this embodiment, the second pinned magnetic sublayer <b>44</b> has a double-layer structure. A magnetic layer <b>42</b> is, for example, composed of a CoFe alloy, and a magnetic layer <b>43</b> is, for example, composed of a Heusler alloy.

[0106] By forming the first pinned magnetic sublayer <b>40</b> using a CoFe alloy, an exchange coupling magnetic field generated between the first antiferromagnetic layer <b>23</b> and the first pinned magnetic sublayer <b>40</b> can be increased, and the magnetization of the first pinned magnetic sublayer <b>40</b> is pinned, for example, in the height direction (in the Y direction).

[0107] On the other hand, the magnetization of the second pinned magnetic sublayer <b>44</b> is pinned in a direction opposite to the magnetization direction of the first pinned magnetic sublayer <b>40</b> by antiferromagnetic interlayer exchange coupling generated between the first pinned magnetic sublayer <b>40</b> and the second pinned magnetic sublayer <b>44</b>. That is, the magnetization of the second pinned magnetic sublayer <b>44</b> is pinned in a direction opposite to the Y direction.

[0108] By forming the magnetic layer <b>42</b> composed of a CoFe alloy at the side of the second pinned magnetic sublayer <b>44</b> in contact with the nonmagnetic intermediate sublayer <b>41</b>, antiferromagnetic interlayer exchange coupling with the first pinned magnetic sublayer <b>40</b> can be strengthened, and the magnetization of the second pinned magnetic sublayer <b>44</b> can be strongly pinned. Element diffusion is also prevented. The nonmagnetic intermediate sublayer <b>41</b> is preferably composed of at least one nonmagnetic conductive material selected from the group consisting of Ru, Rh Ir, Os, Cr, Re, and Cu. The thickness of the nonmagnetic intermediate sublayer <b>41</b> is preferably 4 to 12 Å, and by forming the nonmagnetic intermediate sublayer <b>41</b> thinly in such a range, the antiferromagnetic interlayer exchange coupling between the first pinned magnetic sublayer <b>40</b> and the second pinned magnetic sublayer <b>44</b> can be strengthened.

[0109] As described above, the magnetic layer <b>43</b> is, for example, composed of a Heusler alloy. The Heusler alloy is, for example, represented by the formula X₂YZ, wherein X is an element selected from the group consisting of groups IIIA to IIB elements of the periodic table, Y is Mn, and Z is at least one element selected from the group consisting of Al, Si, Ga, Ge, In, Sn, Tl, Pb, and Sb. The Heusler alloy is a ferromagnetic and half-metallic alloy layer. Herein, the “half-metallic” property corresponds to a polarizability P of 0.5 or more. The polarizability P is represented by the relationship P=(N↑−N↓)/(N↑+N↓), where −1≦P≦1, N↑ is the number of spin-up conduction electrons in the vicinity of the Fermi level, and N↓ is the number of spin-down conduction electrons in the vicinity of the Fermi level. The conduction electrons in the vicinity of the Fermi level actually contribute to conduction.

[0110] By providing the magnetic layer <b>43</b> composed of a Heusler alloy in the vicinity of the interface with the first nonmagnetic layer <b>25</b>, the change in resistance AR can be increased, and the rate of change in resistance (ΔR/R) can be appropriately improved.

[0111] The magnetic layer <b>43</b> may be composed of La_0.7Sr_0.3MnO₃, CrO₂, or F₃O₄instead of the Heusler alloy. These are also ferromagnetic and half-metallic alloys. The magnetic layer <b>43</b> may also be composed of a commonly used ferromagnetic material, such as a CoFe alloy.

[0112] In the embodiment shown in FIG. 2, the free magnetic layer <b>26</b> has a septuple-layer structure. The magnetic layer <b>45</b>, for example, composed of a Heusler alloy, the magnetic layer <b>46</b>, for example, composed of a NiFe alloy, and the magnetic layer <b>47</b>, for example, composed of a CoFe alloy constitute the second free magnetic sublayer <b>48</b>.

[0113] As described above, by disposing the magnetic layer <b>45</b> composed of a Heusler alloy at the interface with the first nonmagnetic layer <b>25</b>, the rate of change in resistance (ΔR/R) can be appropriately improved. By disposing the magnetic layer <b>47</b> composed of a CoFe alloy at the interface with the nonmagnetic intermediate sublayer <b>49</b>, the antiferromagnetic interlayer exchange coupling generated between the first free magnetic sublayer <b>53</b> and the magnetic layer <b>47</b> can be strengthened, and the magnetization directions of the first free magnetic sublayer <b>53</b> and the second free magnetic sublayer <b>48</b> can be maintained in the antiparallel state properly.

[0114] Additionally, when the second free magnetic sublayer <b>48</b> is entirely composed of a Heusler alloy, a CoFe alloy, or the like, the sensitivity of the second free magnetic sublayer <b>48</b> is slightly degraded. Therefore, by inserting the magnetic layer <b>46</b> composed of a NiFe alloy in the center of the second free magnetic sublayer <b>48</b>, the sensitivity of the second magnetic sublayer <b>48</b> to an external magnetic field is increased.

[0115] As shown in FIG. 2, the nonmagnetic intermediate sublayer <b>49</b> is disposed on the second free magnetic sublayer <b>48</b>, and preferably, the nonmagnetic intermediate sublayer <b>49</b> is composed of at least one nonmagnetic conductive material selected from the group consisting of Ru, Rh, Ir, Os, Cr, Re, and Cu. The thickness of the nonmagnetic intermediate sublayer <b>49</b> is preferably 4 to 12 Å, and by forming the nonmagnetic intermediate sublayer <b>49</b> thinly in such a range, the antiferromagnetic interlayer exchange coupling between the first free magnetic sublayer <b>53</b> and the second free magnetic sublayer <b>48</b> can be strengthened.

[0116] In FIG. 2, a layer <b>50</b> is a magnetic layer, for example, composed of a CoFe alloy, a layer <b>51</b> is a magnetic layer, for example, composed of a NiFe alloy, and a layer <b>52</b> is a magnetic layer, for example, composed of a CoFe alloy. The magnetic layers <b>50</b> to <b>52</b> constitute the first free magnetic sublayer <b>53</b>.

[0117] By disposing the magnetic layer <b>50</b> composed of the CoFe alloy at the interface with the nonmagnetic intermediate sublayer <b>49</b>, antiferromagnetic interlayer exchange coupling generated between the second free magnetic sublayer <b>48</b> and the magnetic layer <b>50</b> can be strengthened, and the second free magnetic sublayer <b>48</b> can be aligned in a single domain state stably. The magnetic layer <b>50</b> also acts as a diffusion-preventing layer which prevents the diffusion of elements into the nonmagnetic intermediate sublayer <b>49</b>.

[0118] By disposing the magnetic layer <b>52</b> composed of the CoFe alloy at the interface with the second nonmagnetic layer <b>32</b>, the unidirectional interlayer exchange coupling generated between the second antiferromagnetic layer <b>33</b> and the magnetic layer <b>52</b> can be set so as to have a proper magnitude stably, and the second free magnetic sublayer <b>48</b> can be aligned into a single domain state stably. The magnetic layer <b>52</b> also acts as a diffusion-preventing layer which prevents the diffusion of elements into the second nonmagnetic layer <b>32</b>.

[0119] Although the first free magnetic sublayer <b>53</b> does not directly contribute to the change in magnetoresistance, if the magnetization of the first free magnetic sublayer <b>53</b> is not reversed appropriately in response to an external magnetic field, the magnetic reversal of the second free magnetic sublayer <b>48</b> is inhibited. Therefore, in order to increase the sensitivity of the first free magnetic sublayer <b>53</b> to an external magnetic field, the magnetic layer <b>51</b> composed of the NiFe alloy is inserted in the center of the first free magnetic sublayer <b>53</b>.

[0120] In the embodiment shown in FIG. 2, end faces <b>35</b><i>a </i>of the multilayer film <b>35</b> in the track width direction (in the X direction) are scraped off from the protective layer <b>34</b> to the middle of the multilayer film <b>35</b>, unlike the continuously etched faces from the protective layer <b>34</b> to the underlayer <b>21</b> shown in FIG. 1. In the embodiment shown in FIG. 2, the end faces <b>35</b><i>a </i>are scraped off to the middle of the magnetic layer <b>42</b> of the second pinned magnetic sublayer <b>44</b>.

[0121] The scraped end faces <b>35</b><i>a </i>of the multilayer film <b>35</b> must extend at least to the lower layer of the free magnetic layer <b>26</b>. As described above, since the track width Tw is determined by the width in the track width direction of the free magnetic layer <b>26</b>, in order to properly meet track narrowing, the width of the free magnetic layer <b>26</b> must be decreased by scraping the end faces <b>35</b><i>a </i>of at least the free magnetic layer <b>26</b>. The end faces <b>35</b><i>a </i>may be scraped to the middle of the layer constituting the pinned magnetic layer <b>24</b> as shown in FIG. 2, or may be scraped to the middle of the first antiferromagnetic layer <b>23</b>. Alternatively, the end faces <b>35</b><i>a </i>may be scraped to both end faces of the underlayer <b>21</b> as in shown in FIG. 1.

[0122]FIG. 3 is a partial sectional view of a magnetic sensing element in a third embodiment of the present invention, viewed from the surface facing a recording medium.

[0123] In the embodiment shown in FIG. 3, the magnetic sensing element has the same structure as that of the magnetic sensing element shown in FIG. 2 except that layers between the underlayer <b>21</b> and the protective layer <b>34</b> in the multilayer film <b>35</b> shown in FIG. 2 are deposited in the reversed order.

[0124] That is, in the embodiment shown in FIG. 3, an second antiferromagnetic layer <b>33</b>, a second nonmagnetic layer <b>32</b>, a first free magnetic sublayer <b>53</b>, a nonmagnetic intermediate sublayer <b>49</b>, a second free magnetic sublayer <b>48</b>, a first nonmagnetic layer <b>25</b>, a second pinned magnetic sublayer <b>44</b>, a nonmagnetic intermediate sublayer <b>41</b>, a first pinned magnetic sublayer <b>40</b>, and a first antiferromagnetic layer <b>23</b> are deposited in that order above an underlayer <b>21</b>. The materials and thicknesses for the individual layers are the same as those described with reference to FIGS. 1 and 2.

[0125] In the embodiment shown in FIG. 3, the second nonmagnetic layer <b>32</b> and the second antiferromagnetic layer <b>33</b> are formed on a surface of the first free magnetic sublayer <b>53</b> opposite to the surface in contact with the nonmagnetic intermediate sublayer <b>49</b>. Unidirectional interlayer exchange coupling is produced between the first free magnetic sublayer <b>53</b> and the second antiferromagnetic layer <b>33</b>, and the first free magnetic sublayer <b>53</b> is aligned in a single domain state in the track width direction. The free magnetic layer <b>26</b> has a multilayered ferrimagnetic structure, and the physical thickness of the free magnetic layer <b>26</b> corresponds to the total thickness of the first free magnetic sublayer <b>53</b> and the second free magnetic sublayer <b>48</b>. Since the physical thickness is increased, the product of the change in resistance ΔR and the area A can be improved and the read output can be improved. Since the magnetic thickness is decreased due to the laminated ferrimagnetic structure, the demagnetizing field of the free magnetic layer <b>26</b> is decreased, and a continuous bias with a proper magnitude can be stably applied from the second antiferromagnetic layer <b>33</b> to the first free magnetic sublayer <b>53</b>. Therefore, it is possible to fabricate a magnetic sensing element with satisfactory read sensitivity In the embodiment shown in FIG. 3, the end faces <b>35</b><i>a </i>of the multilayer film <b>35</b> must be scraped off by etching at least to the end faces of the second free magnetic sublayer <b>48</b>. The reason for this is that the second free magnetic sublayer <b>48</b> is the layer which actually contributes to the magnetoresistance effect, and the track width Tw is determined by the width in the track width direction of the second free magnetic sublayer <b>48</b>. In the embodiment shown in FIG. 3, etching is performed to the end faces of the middle of the first free magnetic sublayer <b>53</b>. Etching may be performed further to the lower layer.

[0126] FIGS. <b>4</b> to <b>6</b> are sectional views which show the steps in a method for fabricating the magnetic sensing element shown in FIG. 2. Since a method for fabricating the magnetic sensing element shown in FIG. 1 is basically the same as that of the magnetic sensing element shown in FIG. 2, the method for fabricating the magnetic sensing element shown in FIG. 2 only will be described. Described below is considered to be a representative fabrication method among several methods for fabricating the magnetic sensing element.

[0127] In a step shown in FIG. 4, a lower shielding layer <b>20</b>, an underlayer <b>21</b>, a seed layer <b>22</b>, a first antiferromagnetic layer <b>23</b>, a first pinned magnetic sublayer <b>40</b>, a nonmagnetic intermediate sublayer <b>41</b>, a second pinned magnetic sublayer <b>44</b>, a first nonmagnetic layer <b>25</b>, a second free magnetic sublayer <b>48</b>, a nonmagnetic intermediate sublayer <b>49</b>, a first free magnetic sublayer <b>53</b>, a second nonmagnetic layer <b>32</b>, and a part of a second antiferromagnetic layer <b>33</b> are continuously formed by sputtering. The materials and the thicknesses therefor are the same as those described with reference to FIGS. 1 and 2.

[0128] The reason for forming only a part of the second antiferromagnetic layer <b>33</b> in the step shown in FIG. 4 is that if the second antiferromagnetic layer <b>33</b> is formed with a large thickness, unidirectional interlayer exchange coupling is also generated between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>53</b> by annealing in a magnetic field to produce an exchange coupling magnetic field between the first antiferromagnetic layer <b>23</b> and the first pinned magnetic sublayer <b>40</b>, and it becomes difficult to align the free magnetic layer <b>26</b> in a single domain state in the track width direction in the subsequent step.

[0129] Therefore, the second antiferromagnetic layer <b>33</b> is formed thinly first such that unidirectional interlayer exchange coupling does not occur between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>53</b> even by annealing in a magnetic field. Specifically, the thickness of the second antiferromagnetic layer <b>33</b> is set at 50 Å or less.

[0130] As shown in FIG. 4, a protective layer <b>60</b>, for example, composed of Ru is formed by sputtering on the second antiferromagnetic layer <b>33</b>. The protective layer <b>60</b> is provided so as to properly prevent the second antiferromagnetic layer <b>33</b> from being oxidized. When the protective layer <b>60</b> is composed of Ru, Cr, or the like, even if the protective layer <b>60</b> is formed at an extremely small thickness, the protective layer <b>60</b> functions as an oxidation-inhibiting layer satisfactorily, which is advantageous compared to a case in which the protective layer <b>60</b> must be formed thickly. The protective layer <b>60</b> is scraped off in the subsequent step, and since the protective layer <b>60</b> is extremely thin, the protective layer <b>60</b> can be removed by an ion milling process with low energy. Thereby, the second antiferromagnetic layer <b>33</b> below the protective layer <b>60</b> is not substantially influenced by ion milling. The thickness of the protective layer <b>60</b> is preferably 10 Å or less, and more preferably 5 Å or less.

[0131] After the multilayer film shown in FIG. 4 is formed, a first annealing process is performed in a first magnetic field. Consequently, an exchange coupling magnetic field is generated between the first antiferromagnetic layer <b>23</b> and the first pinned magnetic sublayer <b>40</b>, and for example, the magnetization of the first pinned magnetic sublayer <b>40</b> is pinned in the height direction (in the Y direction). On the other hand, the magnetization of the second pinned magnetic layer <b>44</b> is pinned in a direction opposite to the Y direction by interlayer coupling between the first pinned magnetic sublayer <b>40</b> and the second pinned magnetic sublayer <b>44</b>. In the first annealing process, for example, the annealing temperature is set at 270° C. and the magnitude of the magnetic field is set at 800 kA/m.

[0132] Next, the protective layer <b>60</b> is scraped off by ion milling with low energy. The protective layer <b>60</b> may be completely removed, or a part of the protective layer <b>60</b> may be left. For example, if the thickness of the remaining protective layer <b>60</b> is 3 Å or less, antiferromagnetic characteristics of the second antiferromagnetic layer <b>33</b> are not degraded.

[0133] In the step shown in FIG. 5, the rest of the second antiferromagnetic layer <b>33</b> is formed by sputtering on the second antiferromagnetic layer <b>33</b> which has been partially formed in the step shown in FIG. 4 to complete the second antiferromagnetic layer <b>33</b> with a predetermined thickness. A protective layer <b>34</b> composed of Ta or the like is formed on the second antiferromagnetic layer <b>33</b>. Additionally, as indicated by dotted lines in FIG. 5, the protective layer <b>60</b> composed of Ru or the like may be partially left, and in such a case, the element constituting the protective layer <b>60</b> is diffused in the second antiferromagnetic layer <b>33</b> in an annealing process subsequently performed in a magnetic field.

[0134] Next, a second annealing process in a second magnetic field is performed. The second annealing process is performed in order to control the magnetization direction of the free magnetic layer <b>26</b>, and the second magnetic field is oriented in the track width direction.

[0135] For example, if the first free magnetic sublayer <b>53</b> is magnetized rightward by the second annealing process, the second free magnetic sublayer <b>48</b> is magnetized leftward in the drawing. In the second annealing process, for example, the annealing temperature is set at 250° C. and the magnitude of the magnetic field is set at 24 kA/m.

[0136] The annealing temperature in the second annealing process must be lower than the blocking temperature at which the exchange coupling magnetic field by the first antiferromagnetic layer <b>23</b> is lost, and the magnitude of the second magnetic field must be smaller than the magnitude of the exchange coupling magnetic field between the first antiferromagnetic layer <b>23</b> and the first pinned magnetic sublayer <b>40</b>. Otherwise, the magnetization of the pinned magnetic layer <b>24</b> is fluctuated by the second annealing process.

[0137] Next, in the step shown in FIG. 6, a resist layer <b>61</b> having a predetermined shape is formed on the protective layer <b>34</b>. The width in the track width direction (in the X direction) of the resist layer <b>61</b> is set as small as possible because the width in the track width direction of the free magnetic layer <b>26</b>, which corresponds to the track width Tw, is restricted by the width of the resist layer <b>61</b>.

[0138] As shown in FIG. 6, end faces <b>35</b><i>a </i>not covered with the resist layer <b>61</b> are scraped off by etching. The insulating layers <b>36</b> shown in FIG. 2 are then formed on the end faces <b>35</b><i>a</i>, and the resist layer <b>61</b> is removed. The upper shielding layer <b>37</b> is formed over the insulating layers <b>36</b> and the protective layer <b>34</b> by plating or sputtering.

[0139] In order to fabricate the magnetic sensing element shown in FIG. 3, layers up to a part of the first antiferromagnetic layer <b>23</b> are formed solidly by sputtering, and the protective layer <b>60</b> composed of Ru or the like described with reference to FIG. 4 is formed thereon. Unidirectional exchange coupling is produced between the second antiferromagnetic layer <b>33</b> and the first free magnetic sublayer <b>53</b> by a first annealing process in a first magnetic field. The protective layer <b>60</b> is scraped off by ion milling with low energy, and the rest of the first antiferromagnetic layer <b>23</b> is formed thereon to complete the first antiferromagnetic layer <b>23</b> with a predetermined thickness. A second annealing process in a second magnetic field is performed to produce an exchange coupling magnetic field between the first antiferromagnetic layer <b>23</b> and the first pinned magnetic sublayer <b>40</b>. The subsequent step is the same as that shown in FIG. 6.

[0140] Additionally, magnetic sensing elements of the present invention can also be used for magnetic heads for tape recording, magnetic sensors, etc., in addition to thin-film magnetic heads built in hard disk apparatuses.

[0141] As described above in detail, in accordance with the present invention, for example, a first antiferromagnetic layer, a pinned magnetic layer, a first nonmagnetic layer, a second free magnetic sublayer, a nonmagnetic intermediate sublayer, a first free magnetic sublayer, a second nonmagnetic layer, and a second antiferromagnetic layer are deposited in that order from the bottom.

[0142] Consequently, unidirectional interlayer exchange coupling is generated between the first free magnetic sublayer and the second antiferromagnetic layer, and the first free magnetic sublayer is aligned in a single domain state in the track width direction. The free magnetic layer has a laminated ferrimagnetic structure. The physical thickness of the free magnetic layer corresponds to the total thickness of the first free magnetic sublayer and the second free magnetic sublayer. Since the physical thickness of the free magnetic layer is increased, the product of a change in resistance ΔR and an area A can be improved, resulting in an improvement in read output. In the laminated ferrimagnetic structure, since the magnetic thickness is decreased, the demagnetizing field of the free magnetic layer is weakened, and it is possible to stably apply a continuous bias with a proper magnitude from the second antiferromagnetic layer to the first free magnetic sublayer. Therefore, it is possible to fabricate a magnetic sensing element with satisfactory read sensitivity η.

[0143] In accordance with the present invention, it is possible to provide a magnetic sensing element in which both read output and read sensitivity can be improved even if the element is miniaturized.