Patent Publication Number: US-11393493-B1

Title: Magnetic head and magnetic recording device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-020441, filed on Feb. 12, 2021; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a magnetic head and a magnetic recording device. 
     BACKGROUND 
     Information is recorded on a magnetic recording medium such as an HDD (Hard Disk Drive) using a magnetic head. It is desired to improve the recording density in the magnetic head and the magnetic recording device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are schematic views illustrating a magnetic head according to a first embodiment; 
         FIG. 2  is a schematic cross-sectional view illustrating a magnetic recording device according to the first embodiment; 
         FIG. 3  is a graph view illustrating characteristics of the magnetic head; 
         FIGS. 4A and 4B  are graph views illustrating characteristics of the magnetic head; 
         FIG. 5  is a graph view illustrating characteristics of the magnetic head; 
         FIGS. 6A and 6B  are schematic plan views illustrating the magnetic head according to the first embodiment; 
         FIGS. 7A and 7B  are schematic views illustrating characteristics of the magnetic head according to the embodiment; 
         FIG. 8  is a schematic view illustrating characteristics of the magnetic head according to the first embodiment; 
         FIG. 9  is a schematic cross-sectional view illustrating the magnetic head according to the embodiment; 
         FIG. 10  is a schematic perspective view illustrating the magnetic recording device according to the embodiment; 
         FIG. 11  is a schematic perspective view illustrating a portion of the magnetic recording device according to the embodiment; 
         FIG. 12  is a schematic perspective view illustrating a magnetic recording device according to the embodiment; and 
         FIGS. 13A and 13B  are schematic perspective views illustrating a portion of the magnetic recording device according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a magnetic recording head includes a first magnetic pole, a second magnetic pole, and a stacked body provided between the first magnetic pole and the second magnetic pole. The stacked body includes a first magnetic layer, a second magnetic layer provided between the first magnetic layer and the second magnetic pole, a first non-magnetic layer provided between the first magnetic layer and the second magnetic layer, a second non-magnetic layer provided between the second magnetic layer and the second magnetic pole, and a third non-magnetic layer provided between the first magnetic pole and the first magnetic layer. The first magnetic layer includes a first element including at least one of Fe, Co, or Ni. The second magnetic layer includes the first element, and a second element including at least one selected from the group consisting of Cr, V, Mn, Ti, and Sc. The first magnetic layer does not include the second element, or a concentration of the second element in the first magnetic layer is lower than a concentration of the second element in the second magnetic layer. A first thickness of the first magnetic layer along a first direction from the first magnetic pole toward the second magnetic pole is not less than 0.25 times and not more than 4 times a second thickness of the second magnetic layer along the first direction. 
     According to one embodiment, a magnetic recording device includes the magnetic head described above, and an electric circuit. The electric circuit is configured to supply a current to the stacked body. The current has a direction from the first magnetic layer toward the second magnetic layer. 
     Various embodiments are described below with reference to the accompanying drawings. 
     The drawings are schematic and conceptual; and the relationships between the thickness and width of portions, the proportions of sizes among portions, etc., are not necessarily the same as the actual values. The dimensions and proportions may be illustrated differently among drawings, even for identical portions. 
     In the specification and drawings, components similar to those described previously or illustrated in an antecedent drawing are marked with like reference numerals, and a detailed description is omitted as appropriate. 
     First Embodiment 
       FIGS. 1A and 1B  are schematic views illustrating a magnetic head according to a first embodiment 
       FIG. 1A  is a cross-sectional view.  FIG. 1B  is a plan view viewed in a direction of an arrow AR 1  of  FIG. 1A . 
       FIG. 2  is a schematic cross-sectional view illustrating a magnetic recording device according to the first embodiment. 
     As shown in  FIG. 2 , a magnetic recording device  210  according to the embodiment includes a magnetic head  110  and an electric circuit  20 D. The magnetic recording device  210  may include a magnetic recording medium  80 . At least the recording operation is performed in the magnetic recording device  210 . In the recording operation, information is recorded on the magnetic recording medium  80  using the magnetic head  110 . 
     The magnetic head  110  includes a recording part  60 . As will be described later, the magnetic head  110  may include a reproducing part. The recording unit  60  includes a first magnetic pole  31 , a second magnetic pole  32 , and a stacked body  20 . The stacked body  20  is provided between the first magnetic pole  31  and the second magnetic pole  32 . 
     For example, the first magnetic pole  31  and the second magnetic pole  32  form a magnetic circuit. The first magnetic pole  31  is, for example, a major magnetic pole. The second magnetic pole  32  is, for example, a trailing shield. 
     The direction from the magnetic recording medium  80  toward the magnetic head  110  is taken as a Z-axis direction. One direction perpendicular to the Z-axis direction is taken as an X-axis direction. The direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction. The Z-axis direction corresponds to, for example, a height direction. The X-axis direction corresponds to, for example, a down track direction. The Y-axis direction corresponds to, for example, a cross-track direction. The magnetic recording medium  80  and the magnetic head  110  move relatively along the down track direction. A magnetic field (recording magnetic field) generated from the magnetic head  110  is applied to a desired position of the magnetic recording medium  80 . The magnetization of the magnetic recording medium  80  at a desired position is controlled in a direction corresponding to the recording magnetic field. As a result, information is recorded on the magnetic recording medium  80 . 
     The direction from the first magnetic pole  31  toward the second magnetic pole  32  is taken as a first direction D 1 . The first direction D 1  substantially follows the X-axis direction. In the embodiment, the first direction D 1  may be inclined at a small angle with respect to the X-axis direction. 
     As shown in  FIG. 2 , a coil  30   c  is provided. In this example, a portion of the coil  30   c  is between the first magnetic pole  31  and the second magnetic pole  32 . In this example, a shield  33  is provided. In the X-axis direction, there is the first magnetic pole  31  between the shield  33  and the second magnetic pole  32 . Another portion of the coil  30   c  is between the shield  33  and the first magnetic pole  31 . An insulating portion  30   i  is provided between these multiple elements. The shield  33  is, for example, a leading shield. The magnetic head  110  may include a side shield (not shown). 
     As shown in  FIG. 2 , a recording current Iw is supplied to the coil  30   c  from a recording circuit  30 D. A recording magnetic field corresponding to the recording current Iw is applied to the magnetic recording medium  80  from the first magnetic pole  31 . 
     As shown in  FIG. 2 , the first magnetic pole  31  includes a medium facing surface  30 F. The medium facing surface  30 F is, for example, ABS (Air Bearing Surface). The medium facing surface  30 F faces, for example, the magnetic recording medium  80 . The medium facing surface  30 F is, for example, along the XY plane. 
     As shown in  FIG. 2 , the electric circuit  20 D is electrically connected to the stacked body  20 . In this example, the stacked body  20  is electrically connected to the first magnetic pole  31  and the second magnetic pole  32 . The magnetic head  110  is provided with a first terminal T 1  and a second terminal T 2 . The first terminal T 1  is electrically connected to the stacked body  20  via a first wiring W 1  and the first magnetic pole  31 . The second terminal T 2  is electrically connected to the stacked body  20  via a second wiring W 2  and the second magnetic pole  32 . From the electric circuit  20 D, for example, a current (for example, a direct current) is supplied to the stacked body  20 . 
     As shown in  FIGS. 1A and 1B , the stacked body  20  includes a first magnetic layer  21 , a second magnetic layer  22 , a third magnetic layer  23 , a first non-magnetic layer  41 , and a second non-magnetic layer  42 , and a third non-magnetic layer  43 . In  FIGS. 1A and 1B , the insulating portion  30   i  is omitted. 
     The second magnetic layer  22  is provided between the first magnetic layer  21  and the second magnetic pole  32 . The first non-magnetic layer  41  is provided between the first magnetic layer  21  and the second magnetic layer  22 . The second non-magnetic layer  42  is provided between the second magnetic layer  22  and the second magnetic pole  32 . The third non-magnetic layer  43  is provided between the first magnetic pole  31  and the first magnetic layer  21 . 
     For example, the third non-magnetic layer  43  may be in contact with the first magnetic pole  31  and the first magnetic layer  21 . The first non-magnetic layer  41  may be in contact with the first magnetic layer  21  and the second magnetic layer  22 . The second non-magnetic layer  42  may be in contact with the second magnetic layer  22  and the second magnetic pole  32 . 
     At least one of the first non-magnetic layer  41 , the second non-magnetic layer  42 , or the third non-magnetic layer  43  includes a third element. The third element includes, for example, at least one selected from the group consisting of Cu, Au, Cr, V, Al, and Ag. In a non-magnetic layer including such a material, for example, high spin transmittance can be obtained. For example, high oscillation strength can be obtained. 
     At least one of the second non-magnetic layer  42  or the third non-magnetic layer  43  may include a fourth element. The fourth element includes, for example, at least one selected from the group consisting of Ru, Jr, Ta, Rh, Pd, Pt, and W. In a non-magnetic layer including such a material, for example, low spin transmittance can be obtained. For example, stable oscillation can be easily obtained. At least one of the second non-magnetic layer  42  or the third non-magnetic layer  43  may include the above-mentioned third element and fourth element. 
     In the embodiment, the first magnetic layer  21  includes a first element. The first element includes at least one of Fe, Co, or Ni. 
     The second magnetic layer  22  includes the first element and a second element. The second element includes at least one selected from the group consisting of Cr, V, Mn, Ti, and Sc. The first magnetic layer  21  does not include the second element. Or, a concentration of the second element in the first magnetic layer  21  is lower than a concentration of the second element in the second magnetic layer  22 . 
     For example, the concentration of the second element in the second magnetic layer  22  is not less than 10 atomic % and not more than 80 atomic %. The second magnetic layer  22  including such a material has, for example, negative spin polarization. On the other hand, for example, the first magnetic layer  21  has positive spin polarization. 
     As shown in  FIG. 1B , a current ic is supplied to such a stacked body  20 . The current ic is supplied from, for example, the electric circuit  20 D described above. As shown in  FIG. 1B , the current ic has a direction from the first magnetic layer  21  toward the second magnetic layer  22 . As shown in  FIG. 1B , an electron flow je accompanying the current ic has a direction from the second magnetic layer  22  toward the first magnetic layer  21 . 
     For example, when the current ic equal to or higher than the threshold value flows through the laminated body  20 , the magnetization of the magnetic layer included in the stacked body  20  oscillates. The stacked body  20  functions as, for example, an STO (Spin-Torque Oscillator). An alternating magnetic field (for example, a high frequency magnetic field) is generated from the stacked body  20  with the oscillation. The alternating magnetic field generated by the stacked body  20  is applied to the magnetic recording medium  80 , and writing to the magnetic recording medium  80  is assisted. For example, MAMR (Microwave Assisted Magnetic Recording) can be performed. 
     In the magnetic head  110 , the first magnetic layer  21  and the second magnetic layer  22  function as, for example, an oscillation layer. For example, the spin torque of negative transmission from the second magnetic layer  22  acts on the first magnetic layer  21 . For example, the spin torque reflected by the first magnetic layer  21  acts on the second magnetic layer  22 . For example, the magnetization of the first magnetic layer  21  and the magnetization of the second magnetic layer  22  rotate while interacting with each other. 
     As shown in  FIG. 1B , the thickness of the first magnetic layer  21  along the first direction (direction from the first magnetic pole  31  to the second magnetic pole  32 ) is taken as a first thickness t 1 . The thickness of the second magnetic layer  22  along the first direction is taken as a second thickness t 2 . In the embodiment, for example, the first thickness t 1  may be the same as the second thickness t 2 . This makes it easier to obtain oscillation, as will be described later. 
     The thickness of the first non-magnetic layer  41  along the first direction is taken as a thickness t 41 . The thickness of the second non-magnetic layer  42  along the first direction is taken as a thickness t 42 . The thickness of the third non-magnetic layer  43  along the first direction is taken as a thickness t 43 . These thicknesses are, for example, not less than 0.5 nm and not more 6 nm. When these thicknesses are not less than 0.5 nm, stable oscillation becomes easy. When these thicknesses are not more than 6 nm, for example, the spin transmittance tends to be high. For example, it is easy to obtain high oscillation intensity. 
     In the following, an example of simulation results regarding the behavior of oscillation in the stacked body  20  will be described. In the simulation model, the configuration shown in  FIG. 1B  is provided. That is, the first magnetic pole  31 , the second magnetic pole  32 , the first magnetic layer  21 , the second magnetic layer  22 , and the first to third non-magnetic layers  41  to  43  are provided. The oscillation characteristics of magnetization when the current is (current above the threshold value) illustrated in  FIG. 1B  is supplied is simulated. In the simulation model, the physical characteristic value of the Fe 70 Co 30  alloy is used as the physical characteristic value of the first magnetic layer  21 . The physical characteristic value of the Fe 70 Cr 30  alloy is used as the physical characteristic value of the second magnetic layer  22 . The physical characteristic value of Cu is used as the physical characteristic value of the first non-magnetic layer  41  and the third non-magnetic layer  43 . The physical characteristic value of Ta is used as the physical characteristic value of the second non-magnetic layer  42 . The thicknesses t 41  to t 43  are 2 nm. 
       FIG. 3  is a graph view illustrating characteristics of the magnetic head. 
     In the simulation illustrated in  FIG. 3 , a sum of the first thickness t 1  of the first magnetic layer  21  and the second thickness t 2  of the second magnetic layer  22  is kept constant at 19 nm, and a ratio of the first thickness t 1  to the second thickness t 2  is changed. The horizontal axis of  FIG. 3  is a thickness ratio R 1 . The thickness ratio R 1  is a ratio of the first thickness t 1  to the second thickness t 2  (that is, t 1 /t 2 ). The vertical axis is oscillation strength OS. The oscillation strength OS is a sum of the product of the amplitude of the magnetization of the first magnetic layer  21  and the first thickness t 1  and the product of the amplitude of the vibration of the magnetization of the second magnetic layer  22  and the second thickness t 2 . When the oscillation strength OS is high, for example, the recording density by MAMR is likely to be improved. 
     As shown in  FIG. 3 , when the thickness ratio R 1  is close to 1, high oscillation strength OS can be obtained. For example, stable oscillation can be obtained when the thickness ratio R 1  is not less than 0.25 and not more than 4. The thickness ratio R 1  may be not less than 0.33. Higher oscillation strength OS can be obtained. The thickness ratio R 1  may be not more than 3. Higher oscillation strength OS can be obtained. 
     In the embodiment, the first thickness t 1  is preferably not less than 0.25 times and not more than 4 times the second thickness t 2 . As a result, the high oscillation strength OS can be obtained. Stable oscillation can be obtained. The first thickness t 1  may be not less than 0.33 times and not more than 3 times of the second thickness. Higher oscillation strength OS can be obtained. More stable oscillation can be obtained. According to the embodiment, stable MAMR can be carried out. It is possible to provide a magnetic head which is possible to improve the recording density. 
       FIGS. 4A and 4B  are graph views illustrating characteristics of the magnetic head. 
     The horizontal axis of  FIG. 4A  is the first thickness t 1 . In  FIG. 4A , the second thickness t 2  is 15 nm. The horizontal axis of  FIG. 4B  is the second thickness t 2 . In  FIG. 4B , the first thickness t 1  is 15 nm. In  FIGS. 4A and 4B , the current is supplied to the stacked body  20  is 2.5×10 8  A/cm 2 . The vertical axis of  FIGS. 4A and 4B  is oscillation strength OS. 
     As shown in  FIG. 4A , the first thickness t 1  is preferably not less than 5 nm. As a result, the high oscillation strength OS can be obtained. The first thickness t 1  may be, for example, not more than 20 nm. For example, the distance between the first magnetic pole  31  and the second magnetic pole  32  (for example, a recording gap) can be shortened. For example, it is easy to obtain a high recording density. 
     As shown in  FIG. 4B , the second thickness t 2  is preferably not less than 5 nm. As a result, the high oscillation strength OS can be obtained. The second thickness t 2  may be not more than 20 nm. For example, the recording gap can be shortened. For example, it is easy to obtain a high recording density. 
       FIG. 5  is a graph view illustrating characteristics of the magnetic head. 
     The horizontal axis of  FIG. 5  is a sum ts of the first thickness t 1  and the second thickness t 2 . The vertical axis is oscillation strength OS. 
     As shown in  FIG. 5 , the sum ts of the first thickness t 1  and the second thickness t 2  is preferably not less than 15 nm. As a result, high oscillation strength OS can be obtained. The sum ts may be not more than 40 nm. For example, the recording gap can be shortened. For example, it is easy to obtain a high recording density. 
       FIGS. 6A and 6B  are schematic plan views illustrating the magnetic head according to the first embodiment. 
     As shown in  FIG. 6A , a magnetic head  111  according to the embodiment includes the first magnetic pole  31 , the second magnetic pole  32 , and the stacked body  20 . Also in the magnetic head  111 , the stacked body  20  includes the first magnetic layer  21 , the second magnetic layer  22 , the first non-magnetic layer  41 , the second non-magnetic layer  42 , and the third non-magnetic layer  43 . In the magnetic head  111 , at least one of the first magnetic layer  21  or the second magnetic layer  22  includes multiple regions. Other configurations of the magnetic head  111  may be the same as those of the magnetic head  110 . 
     For example, the first magnetic layer  21  includes a first magnetic region  21   a  and a second magnetic region  21   b . The second magnetic region  21   b  is between the first magnetic region  21   a  and the first non-magnetic layer  41 . For example, saturation magnetization of the first magnetic region  21   a  is larger than saturation magnetization of the second magnetic region  21   b . This makes it easy to obtain stable oscillation, for example. 
     For example, the saturation magnetization of the first magnetic region  21   a  is not less than 1.2 times the saturation magnetization of the second magnetic region  21   b . As a result, stable oscillation can be easily obtained. The saturation magnetization of the first magnetic region  21   a  may be not more than 3 times the saturation magnetization of the second magnetic region  21   b . As a result, stable oscillation can be easily obtained. 
     For example, a concentration of Fe in the first magnetic region  21   a  is higher than a concentration of Fe in the second magnetic region  21   b . For example, the saturation magnetization of the first magnetic region  21   a  tends to be larger than the saturation magnetization of the second magnetic region  21   b . For example, a concentration of Ni in the first magnetic region  21   a  is lower than a concentration of Ni in the second magnetic region  21   b . As a result, for example, the saturation magnetization of the first magnetic region  21   a  tends to be larger than the saturation magnetization of the second magnetic region  21   b . The boundary between the first magnetic region  21   a  and the second magnetic region  21   b  may be clear or unclear. 
     For example, the second magnetic layer  22  includes a third magnetic region  22   c  and a fourth magnetic region  22   d . The fourth magnetic region  22   d  is between the third magnetic region  22   c  and the first non-magnetic layer  41 . For example, saturation magnetization of the third magnetic region  22   c  is larger than saturation magnetization of the fourth magnetic region  22   d . This makes it easy to obtain stable oscillation, for example. 
     For example, the saturation magnetization of the third magnetic region  22   c  is not less than 1.2 times the saturation magnetization of the fourth magnetic region  22   d . This makes it easy to obtain stable oscillation. The saturation magnetization of the third magnetic region  22   c  may be not more than 3 times the saturation magnetization of the fourth magnetic region  22   d . This makes it easy to obtain stable oscillation. 
     For example, a concentration of Fe in the third magnetic region  22   c  is higher than a concentration of Fe in the fourth magnetic region  22   d . As a result, for example, the saturation magnetization of the third magnetic region  22   c  tends to be larger than the saturation magnetization of the fourth magnetic region  22   d . For example, a concentration of the second element in the third magnetic region  22   c  is lower than a concentration of the second element in the fourth magnetic region  22   d . As a result, for example, the saturation magnetization of the third magnetic region  22   c  tends to be larger than the saturation magnetization of the fourth magnetic region  22   d . The boundary between the third magnetic region  22   c  and the fourth magnetic region  22   d  may be clear or unclear. 
     As shown in  FIG. 6B , a magnetic head  112  according to the embodiment includes the first magnetic pole  31 , the second magnetic pole  32 , and the stack body  20 . In the magnetic head  112 , the stacked body  20  includes a third magnetic layer  23  in addition to the first magnetic layer  21 , the second magnetic layer  22 , the first non-magnetic layer  41 , the second non-magnetic layer  42 , and the third non-magnetic layer  43 . Other configurations of the magnetic head  112  may be the same as those of the magnetic head  110  or the magnetic head  111 . 
     The third magnetic layer  23  is provided between the second magnetic layer  22  and the second non-magnetic layer  42 . The third magnetic layer  23  includes the first element including at least one of Fe, Co, or Ni. The third magnetic layer  23  does not include the second element. Or, a concentration of the second element in the third magnetic layer  23  is lower than a concentration of the second element in the second magnetic layer  22 . As described above, the second element includes at least one selected from the group consisting of Cr, V, Mn, Ti, and Sc. 
     For example, saturation magnetization of the third magnetic layer  23  is higher than saturation magnetization of the second magnetic layer  22 . This makes it easy to obtain stable oscillation, for example. The boundary between the third magnetic layer  23  and the first magnetic layer  21  may be clear or unclear. The third magnetic layer  23  may be continuous with the second magnetic layer  22 . 
     In the magnetic head  112 , the first thickness t 1  of the first magnetic layer  21  is, for example, not less than 0.8 times and not more than 1.25 times a sum of the third thickness t 3  of the third magnetic layer  23  along the first direction (direction from the first magnetic pole  31  toward the second magnetic pole  32 ) and the second thickness t 2  of the second magnetic layer  22 . For example, high oscillation strength OS can be obtained. Stable oscillation can be obtained. 
       FIGS. 7A and 7B  are schematic views illustrating characteristics of the magnetic head according to the embodiment. 
     The horizontal axis of  FIGS. 7A and 7B  is the recording current Iw flowing through the coil  30   c . The recording magnetic field generated from at least one of the first magnetic pole  31  or the second magnetic pole  32  changes according to the recording current Iw flowing through the coil  30   c . The recording magnetic field is applied to the stacked body  20 . Therefore, the horizontal axis corresponds to the magnetic field applied to the stacked body  20 . The vertical axis of  FIGS. 7A and 7B  is an electrical resistance Rx of the stacked body  20 . 
     In  FIG. 7A , the current ic supplied to the stacked body  20  is smaller than a threshold current Ith of oscillation. In the example of  FIG. 7A , the current ic is, for example, 1.0×10 6  A/cm 2 . In  FIG. 7B , the current ic supplied to the stacked body  20  is larger than the threshold current Ith. In the example of  FIG. 7B , the current ic is 1.0×10 8  A/cm 2 . The current ic in  FIG. 7B  is 100 times the current ic in  FIG. 7A .  FIG. 7A  corresponds to characteristics in the non-oscillating state.  FIG. 7B  corresponds to characteristics in the oscillating state. These figures illustrate characteristics of the temporal average value of the electrical resistance Rx. When the stacked body  20  is oscillating, the electrical resistance Rx changes with the oscillation. A temporal average resistance is adopted as the electrical resistance Rx. The time average can also suppress the influence of noise, for example. 
     As shown in  FIG. 7A , in a case where the current ic is sufficiently smaller than the threshold current Ith, the electrical resistance Rx increases as the absolute value of the recording current Iw (that is, the magnetic field) increases. When the absolute value of the recording current Iw is sufficiently large, the electrical resistance Rx is saturated. For example, the recording current Iw when the electrical resistance Rx is saturated is, for example, 50 mA. The magnetic field at this time is about 15,000 Oe. 
     In the magnetic recording device head according to the embodiment, for example, the characteristics illustrated in  FIG. 7A  occur. As shown in  FIG. 7A , the electrical resistance Rx of the stacked body  20  is a first resistance Rx 1  when the recording current Iw is a first current I1. The electrical resistance Rx is a second resistance Rx 2  when the recording current Iw is a second current I2. The electrical resistance Rx is a third resistance Rx 3  when the recording current Iw is a third current I3. The absolute value of the first current I1 is smaller than the absolute value of the second current I2 and smaller than the absolute value of the third current I3. The direction of the second current I2 is opposite to the direction of the third current I3. The first resistance Rx 1  is lower than the second resistance Rx 2  and is lower than the third resistance Rx 3 . For example, a valley-shaped current-resistance characteristic occurs. The first current I1 may be substantially 0. 
     As shown in  FIG. 7B , in a case where the current ic is larger than the threshold current Ith and oscillation occurs, the electric resistance Rx shows the characteristics of peaks and valleys. In this case as well, if the absolute values of the second current I2 and the third current I3 are sufficiently large, it can be regarded as a valley-shaped characteristic. For example, the absolute values of the second current I2 and the third current I3 may be values when the electric resistance Rx is saturated in a case where the current ic is sufficiently smaller than the threshold current Ith. Also in this case, the first resistance Rx 1  is lower than the second resistance Rx 2  and is lower than the third resistance Rx 3 . On the other hand, in a general STO, a mountain-shaped characteristic occurs. The valley-shaped characteristics in the embodiment are considered to be specific characteristics depending on the configuration according to the embodiment. 
     Such specific characteristics may be related to the fact that the first magnetic layer  21  has positive polarization and the second magnetic layer  22  has negative polarization. In such a combination, in a case where the absolute value of the recording current Iw is large (that is, a case where the absolute value of the magnetic field is large), the directions of magnetization of the first magnetic layer  21  and the second magnetic layer  22  are close to parallel to each other, and the resistance is considered to be increasing. In a general STO, each magnetic layer has positive polarization. The resistance decreases when the magnetization directions are close to parallel to each other. 
       FIG. 8  is a schematic view illustrating characteristics of the magnetic head according to the first embodiment. 
     The horizontal axis in  FIG. 8  is a time tm. The vertical axis is magnetization Mz (normalized value).  FIG. 8  shows an example relating to magnetization Mz 1  of the first magnetic layer  21  and magnetization Mz 2  of the second magnetic layer  22 . As shown in  FIG. 8 , the magnetization Mz 1  and the magnetization Mz 2  rotate in opposite phases (for example, in a state where the opposite directions are kept). 
     In the following, an example of the magnetic head and the magnetic recording medium  80  included in the magnetic recording device  210  according to the embodiment will be described. 
       FIG. 9  is a schematic cross-sectional view illustrating the magnetic head according to the embodiment. 
     As shown in  FIG. 9 , in the magnetic head according to the embodiment (for example, the magnetic head  110 ), the first direction D 1  from the first magnetic pole  31  toward the second magnetic pole  32  may be inclined with respect to the X-axis direction. The first direction D 1  corresponds to the stacking direction of the stacked body  20 . The X-axis direction is along the medium facing surface  30 F. The angle between the first direction D 1  and the medium facing surface  30 F is taken as an angle θ 1 . The angle θ 1  is, for example, not less than 15 degrees and not more than 30 degrees. The angle Al may be 0 degrees. 
     When the first direction D 1  is inclined with respect to the X-axis direction, the thickness of the layer corresponds to the length along the first direction D 1 . The configuration in which the first direction D 1  is inclined with respect to the X-axis direction may be applied to any magnetic head according to the embodiment. For example, the interface between the first magnetic pole  31  and the laminated body  20  and the interface between the stacked body  20  and the second magnetic pole  32  may be inclined with respect to the X-axis direction. 
     In the following, an example of the magnetic head and the magnetic recording medium  80  included in the magnetic recording device  210  according to the embodiment will be described. 
       FIG. 10  is a schematic perspective view illustrating the magnetic recording device according to the embodiment. 
     As shown in  FIG. 10 , the magnetic head according to the embodiment (for example, the magnetic head  110 ) is used together with the magnetic recording medium  80 . In this example, the magnetic head  110  includes the recording part  60  and the reproducing part  70 . Information is recorded on the magnetic recording medium  80  by the recording part  60  of the magnetic head  110 . The reproducing part  70  reproduces the information recorded on the magnetic recording medium  80 . 
     The magnetic recording medium  80  includes, for example, a medium substrate  82  and a magnetic recording layer  81  provided on the medium substrate  82 . The magnetization  83  of the magnetic recording layer  81  is controlled by the recording part  60 . 
     The reproducing part  70  includes, for example, a first reproducing magnetic shield  72   a , a second reproducing magnetic shield  72   b , and a magnetic reproducing element  71 . The magnetic reproducing element  71  is provided between the first reproducing magnetic shield  72   a  and the second reproducing magnetic shield  72   b . The magnetic reproducing element  71  is possible to output a signal corresponding to the magnetization  83  of the magnetic recording layer  81 . 
     As shown in  FIG. 10 , the magnetic recording medium  80  moves relative to the magnetic head  110  in a direction of the medium movement direction  85 . The magnetic head  110  controls the information corresponding to the magnetization  83  of the magnetic recording layer  81  at an arbitrary position. The magnetic head  110  reproduces information corresponding to the magnetization  83  of the magnetic recording layer  81  at an arbitrary position. 
       FIG. 11  is a schematic perspective view illustrating a portion of the magnetic recording device according to the embodiment. 
       FIG. 11  illustrates a head slider. 
     The magnetic head  110  is provided on a head slider  159 . The head slider  159  includes, for example, Al 2 O 3 /TiC and the like. The head slider  159  moves relative to the magnetic recording medium while floating or contacting the magnetic recording medium. 
     The head slider  159  includes, for example, an air inflow side  159 A and an air outflow side  159 B. The magnetic head  110  is arranged on the side surface of the air outflow side  159 B of the head slider  159 . As a result, the magnetic head  110  moves relative to the magnetic recording medium while floating or contacting the magnetic recording medium. 
       FIG. 12  is a schematic perspective view illustrating a magnetic recording device according to the embodiment. 
     As shown in  FIG. 12 , in the magnetic recording device  150  according to the embodiment, a rotary actuator is used. A recording medium disc  180  is mounted on a spindle motor  180 M. The recording medium disc  180  is rotated in the direction of an arrow AR by the spindle motor  180 M. The spindle motor  180 M responds to a control signal from the drive device controller. The magnetic recording device  150  according to the embodiment may include multiple recording medium disks  180 . The magnetic recording device  150  may include a recording medium  181 . The recording medium  181  is, for example, an SSD (Solid State Drive). As the recording medium  181 , for example, a non-volatile memory such as a flash memory is used. For example, the magnetic recording device  150  may be a hybrid HDD (Hard Disk Drive). 
     The head slider  159  records and reproduces the information to be recorded on the recording medium disk  180 . The head slider  159  is provided at the tip of the thin film suspension  154 . A magnetic head according to the embodiment is provided near the tip of the head slider  159 . 
     When the recording medium disk  180  rotates, the pressing pressure by a suspension  154  and the pressure generated on the medium facing surface (ABS) of the head slider  159  are balanced. The distance between the media facing surface of the head slider  159  and the surface of the recording medium disc  180  is a predetermined fly height. In the embodiment, the head slider  159  may contact the recording medium disc  180 . For example, a contact-sliding type may be applied. 
     The suspension  154  is connected to one end of an arm  155  (e.g., an actuator arm). The arm  155  includes, for example, a bobbin portion and the like. The bobbin portion holds the drive coil. A voice coil motor  156  is provided at the other end of the arm  155 . The voice coil motor  156  is a kind of linear motor. The voice coil motor  156  includes, for example, a drive coil and a magnetic circuit. The drive coil is wound around the bobbin portion of the arm  155 . The magnetic circuit includes a permanent magnet and an opposed yoke. A drive coil is provided between the permanent magnet and the opposing yoke. The suspension  154  has one end and the other end. The magnetic head is provided at one end of the suspension  154 . The arm  155  is connected to the other end of the suspension  154 . 
     The arm  155  is held by a ball bearing. Ball bearings are provided at two locations above and below the bearing part  157 . The arm  155  can be rotated and slid by the voice coil motor  156 . The magnetic head can be moved to an arbitrary position on the recording medium disk  180 . 
       FIGS. 13A and 13B  are schematic perspective views illustrating a portion of the magnetic recording device according to the embodiment. 
       FIG. 13A  illustrates a partial configuration of the magnetic recording device and is an enlarged perspective view of a head stack assembly  160 .  FIG. 13B  is a perspective view illustrating a magnetic head assembly (head gimbal assembly: HGA)  158  that is a portion of the head stack assembly  160 . 
     As shown in  FIG. 13A , the head stack assembly  160  includes the bearing part  157 , the head gimbal assembly  158 , and a support frame  161 . The head gimbal assembly  158  extends from the bearing part  157 . The support frame  161  extends from the bearing part  157 . The extending direction of the support frame  161  is opposite to the extending direction of the head gimbal assembly  158 . The support frame  161  supports a coil  162  of the voice coil motor  156 . 
     As shown in  FIG. 13B , the head gimbal assembly  158  includes the arm  155  extending from the bearing part  157  and the suspension  154  extending from the arm  155 . 
     The head slider  159  is provided at the tip of the suspension  154 . The head slider  159  is provided with the magnetic head according to the embodiment. 
     The magnetic head assembly (head gimbal assembly)  158  according to the embodiment includes the magnetic head according to the embodiment, the head slider  159  provided with the magnetic head, the suspension  154 , and the arm  155 . The head slider  159  is provided at one end of the suspension  154 . The arm  155  is connected to the other end of the suspension  154 . 
     The suspension  154  includes, for example, lead wires (not shown) for recording and reproducing signals. The suspension  154  may include, for example, a lead wire (not shown) for a heater for adjusting the fly height. The suspension  154  may include, for example, a lead wire (not shown) for a spin transfer torque oscillator. These lead wires and multiple electrodes provided on the magnetic head are electrically connected. 
     The magnetic recording device  150  is provided with a signal processor  190 . The signal processor  190  records and reproduces a signal on a magnetic recording medium using a magnetic head. In the signal processor  190 , the input/output lines of the signal processor  190  are connected to, for example, the electrode pads of the head gimbal assembly  158 , and are electrically connected to the magnetic head. 
     The magnetic recording device  150  according to the embodiment includes the magnetic recording medium, the magnetic head according to the embodiment, a movable part, a position controller, and the signal processor. The movable part is relatively movable in a state where the magnetic recording medium and the magnetic head are separated or brought into contact with each other. The position controller aligns the magnetic head with a predetermined recording position on the magnetic recording medium. The signal processor records and reproduces a signal on a magnetic recording medium using a magnetic head. 
     For example, as the above-mentioned magnetic recording medium, the recording medium disk  180  is used. The movable part includes, for example, the head slider  159 . The position controller includes, for example, the head gimbal assembly  158 . 
     The embodiment may include the following configurations (e.g., technical proposals). 
     Configuration 1 
     A magnetic recording head, comprising: 
     a first magnetic pole; 
     a second magnetic pole; and 
     a stacked body provided between the first magnetic pole and the second magnetic pole, 
     the stacked body including
         a first magnetic layer,   a second magnetic layer provided between the first magnetic layer and the second magnetic pole,   a first non-magnetic layer provided between the first magnetic layer and the second magnetic layer,   a second non-magnetic layer provided between the second magnetic layer and the second magnetic pole, and   a third non-magnetic layer provided between the first magnetic pole and the first magnetic layer,       

     the first magnetic layer including a first element including at least one of Fe, Co, or Ni, 
     the second magnetic layer including the first element, and a second element including at least one selected from the group consisting of Cr, V, Mn, Ti, and Sc, 
     the first magnetic layer not including the second element, or a concentration of the second element in the first magnetic layer being lower than a concentration of the second element in the second magnetic layer, and 
     a first thickness of the first magnetic layer along a first direction from the first magnetic pole toward the second magnetic pole being not less than 0.25 times and not more than 4 times a second thickness of the second magnetic layer along the first direction. 
     Configuration 2 
     The magnetic head according to Configuration 1, wherein the first thickness is not less than 0.33 times the second thickness. 
     Configuration 3 
     The magnetic head according to Configuration 1 or 2, wherein 
     the third non-magnetic layer contacts the first magnetic pole and the first magnetic layer. 
     Configuration 4 
     The magnetic head according to one of Configurations 1 to 3, wherein 
     the first non-magnetic layer contacts the first magnetic layer and the second magnetic layer. 
     Configuration 5 
     The magnetic head according to one of Configurations 1 to 4, wherein 
     the second non-magnetic layer contacts the second magnetic layer and the second magnetic pole. 
     Configuration 6 
     The magnetic head according to Configuration 1, wherein 
     at least one of the first non-magnetic layer, the second non-magnetic layer, or the third non-magnetic layer includes a third element including at least one selected from the group consisting of Cu, Au, Cr, V, Al, or Ag. 
     Configuration 7 
     The magnetic head according to one of Configurations 1 to 6, wherein 
     the second thickness is not less than 5 nm. 
     Configuration 8 
     The magnetic head according to one of Configurations 1 to 7, wherein 
     the first thickness is not less than 5 nm. 
     Configuration 9 
     The magnetic head according to one of Configurations 1 to 8, wherein 
     a sum of the first thickness and the second thickness is not less than 15 nm. 
     Configuration 10 
     The magnetic head according to one of Configurations 1 to 9, wherein 
     the first magnetic layer includes a first magnetic region and a second magnetic region, 
     the second magnetic region is between the first magnetic region and the first non-magnetic layer, and 
     saturation magnetization of the first magnetic region is larger than saturation magnetization of the second magnetic region. 
     Configuration 11 
     The magnetic head according to one of Configurations 1 to 9, wherein 
     the first magnetic layer includes a first magnetic region and a second magnetic region, 
     the second magnetic region is between the first magnetic region and the first non-magnetic layer, and 
     a concentration of Fe in the first magnetic region is higher than a concentration of Fe in the second magnetic region. 
     Configuration 12 
     The magnetic head according to one of Configurations 1 to 11, wherein 
     the second magnetic layer includes a third magnetic region and a fourth magnetic region, 
     the fourth magnetic region is between the third magnetic region and the first non-magnetic layer, and 
     saturation magnetization of the third magnetic region is larger than saturation magnetization of the fourth magnetic region. 
     Configuration 13 
     The magnetic head according to one of configurations 1 to 12, wherein 
     the second magnetic layer includes a third magnetic region and a fourth magnetic region, 
     the fourth magnetic region is between the third magnetic region and the first non-magnetic layer, and 
     a concentration of Fe in the third magnetic region is higher than a concentration of Fe in the fourth magnetic region. 
     Configuration 14 
     The magnetic head according to one of Configurations 1 to 13, wherein 
     the stacked body further includes a third magnetic layer, 
     the third magnetic layer is provided between the second magnetic layer and the second non-magnetic layer, 
     the third magnetic layer includes a first element including at least one of Fe, Co, or Ni, and 
     the third magnetic layer does not include the second element, or a concentration of the second element in the third magnetic layer is lower than a concentration of the second element in the second magnetic layer. 
     Configuration 15 
     The magnetic head according to one of Configurations 1 to 14, wherein 
     a concentration of the second element in the second magnetic layer is not less than 10 atomic % and not more than 80 atomic %. 
     Configuration 16 
     The magnetic head according to one of Configurations 1 to 15, wherein 
     a current is supplied to the stacked body in a direction from the first magnetic layer toward the second magnetic layer. 
     Configuration 17 
     The magnetic head according to Configurations 16, wherein 
     an alternating magnetic field is generated from the stacked body when the current is supplied to the stacked body. 
     Configuration 18 
     The magnetic head according to one of Configurations 1 to 17, further comprising: 
     a coil, 
     a recording magnetic field generated from at least one of the first magnetic pole or the second magnetic pole changing according to a recording current flowing through the coil, 
     an electrical resistance of the stacked body being a first resistance when the recording current is a first current, 
     the electrical resistance being a second resistance when the recording current is a second current, 
     the electrical resistance being a third resistance when the recording current is a third current, 
     an absolute value of the first current being smaller than an absolute value of the second current, and being smaller than an absolute value of the third current, 
     a direction of the second current being opposite to a direction of the third current, and 
     the first resistance being lower than the second resistance, and being lower than the third resistance. 
     Configuration 19 
     A magnetic recording device, comprising: 
     the magnetic head according to one of Configurations 1 to 16; and 
     an electric circuit, 
     the electric circuit being configured to supply a current to the stacked body, and 
     the current having a direction from the first magnetic layer toward the second magnetic layer. 
     Configuration 20 
     The magnetic recording device according to Configuration 19, wherein 
     when the electric circuit supplies a current to the stacked body, an alternating magnetic field is generated from the stacked body. 
     According to the embodiment, a magnetic head and a magnetic recording device, in which a recording density is possible to be improved, can be provided. 
     In the specification of the application, “perpendicular” and “parallel” refer to not only strictly perpendicular and strictly parallel but also include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular and substantially parallel. 
     Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the embodiments of the invention are not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in magnetic heads such as magnetic poles, stacked bodies, magnetic layers, non-magnetic layers, wirings, etc., from known art. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained. 
     Further, any two or more components of the specific examples may be combined within the extent of technical feasibility and are included in the scope of the invention to the extent that the purport of the invention is included. 
     Moreover, all magnetic heads, and magnetic recording devices practicable by an appropriate design modification by one skilled in the art based on the magnetic heads, and the magnetic recording devices described above as embodiments of the invention also are within the scope of the invention to the extent that the purport of the invention is included. 
     Various other variations and modifications can be conceived by those skilled in the art within the spirit of the invention, and it is understood that such variations and modifications are also encompassed within the scope of the invention. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.