Magnetic head and magnetic recording device

Abstract

Embodiments of the present invention provide a magnetic head and a magnetic recording device capable of improving recording density. According to the embodiment, the magnetic head includes a first and second magnetic poles and a laminate. The laminate includes a first magnetic layer, a second magnetic layer disposed between the second magnetic pole and the first magnetic layer, a third magnetic layer disposed between the second magnetic pole and the second magnetic layer, a fourth magnetic layer disposed between the second magnetic pole and the third magnetic layer, a first non-magnetic layer disposed between the first magnetic layer and the first magnetic pole, a second non-magnetic layer disposed between the second magnetic layer and the first magnetic layer, a third non-magnetic layer disposed between the third magnetic layer and the second magnetic layer, a fourth non-magnetic layer disposed between the fourth magnetic layer and the third magnetic layer, and a fifth non-magnetic layer disposed between the second magnetic pole and the fourth magnetic layer. The second non-magnetic layer is connected to the second and first magnetic layers. The third non-magnetic layer is connected to the third and second magnetic layers. The fourth non-magnetic layer is connected to the fourth and third magnetic layers.

Description

[0001] This application is based on Japanese Patent Application No. 2021-028528 (filing date: February 25, 2021) and claims the benefit of priority from the prior application, and the present application incorporates all the contents of the prior application by reference. Technical Field

[0002] Embodiments of the present invention relate to a magnetic head and a magnetic recording device. Background Art

[0003] A magnetic head is used to record information on a magnetic recording medium such as a HDD (Hard Disk Drive). In the magnetic head and the magnetic recording device, it is desired to increase the recording density. Summary of the invention

[0004] Embodiments of the present invention provide a magnetic head and a magnetic recording device capable of improving recording density.

[0005] Means for solving problems

[0006] According to an embodiment of the present invention, a magnetic head has a first magnetic pole, a second magnetic pole, and a stacked body disposed between the first magnetic pole and the second magnetic pole. The stacked body includes a first magnetic layer, a second magnetic layer disposed between the second magnetic pole and the first magnetic layer, a third magnetic layer disposed between the second magnetic pole and the second magnetic layer, a fourth magnetic layer disposed between the second magnetic pole and the third magnetic layer, a first non-magnetic layer disposed between the first magnetic layer and the first magnetic pole, a second non-magnetic layer disposed between the second magnetic layer and the first magnetic layer, a third non-magnetic layer disposed between the third magnetic layer and the second magnetic layer, a fourth non-magnetic layer disposed between the fourth magnetic layer and the third magnetic layer, and a fifth non-magnetic layer disposed between the second magnetic pole and the fourth magnetic layer. The second non-magnetic layer is in contact with the second magnetic layer and the first magnetic layer. The third non-magnetic layer is in contact with the third magnetic layer and the second magnetic layer. The fourth non-magnetic layer is in contact with the fourth magnetic layer and the third magnetic layer.

[0007] According to the magnetic head having the above-mentioned structure, it is possible to provide a magnetic head and a magnetic recording device capable of improving the recording density. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 (a) and Figure 1 (b) is a schematic diagram illustrating the magnetic head according to the first embodiment.

[0009] Figure 2 This is a schematic cross-sectional view illustrating the magnetic recording device according to the first embodiment.

[0010] Figure 3 is a graph illustrating the characteristics of the magnetic head.

[0011] Figure 4 (a)~ Figure 4 (d) is a graph illustrating the characteristics of the magnetic head.

[0012] Figure 5 (a)~ Figure 5 (c) is a graph illustrating the characteristics of the magnetic head.

[0013] Figure 6 (a)~ Figure 6 (c) is a graph illustrating the characteristics of the magnetic head.

[0014] Figure 7 It is a schematic cross-sectional view illustrating a magnetic head according to the embodiment.

[0015] Figure 8 It is a schematic perspective view illustrating a magnetic recording device according to an embodiment.

[0016] Fig. 9 This is a schematic perspective view illustrating a part of the magnetic recording device according to the embodiment.

[0017] Fig.10 It is a schematic perspective view illustrating a magnetic recording device according to an embodiment.

[0018] Fig.11 (a) and Fig.11 (b) is a schematic perspective view illustrating a part of the magnetic recording device according to the embodiment.

[0019]

Number Description

[0020] 20…Layered body, 20D…Circuit, 21-24…1st to 4th magnetic layers, 30D…Recording circuit, 30F…Medium facing surface, 30c…Coil, 30i…Insulating portion, 31, 32…1st and 2nd magnetic poles, 33…Shield, 41-45…1st to 5th non-magnetic layers, 60…Recording portion, 70…Reproducing portion, 71…Magnetic reproducing element, 72a, 72b…1st and 2nd reproducing magnetic shield, 80…Magnetic recording medium, 81…Magnetic recording layer, 82…Medium substrate, 83…Magnetization, 85…Medium moving direction, θ1…Angle, 110…Magnetic head, 150…Magnetic recording device, 154…Suspension, 155…Arm, 156…Voice coil motor, 157…Bearing portion, 158…Head gimbal assembly, 159…Head Slider, 159A…air inflow side, 159B…air outflow side, 160…head stack assembly, 161…support, 162…coil, 180…recording medium disk, 180M…spindle motor, 181…recording medium, 190…signal processing unit, 210…magnetic recording device, AR, AR1…arrow, D1…first direction, H1…magnetic field, Iw…recording current, OS…oscillation intensity, MD1 to MD3…first to third modes, OS…oscillation intensity, R21, R23, R31, R41, R42, R43…ratio, T1, T2…first and second terminals, W1, W2…first and second wirings, ic…current, je…electron flow, t1 to t4…first to fourth thicknesses, t41 to t45…thickness DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022] The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the size between parts, etc. are not necessarily the same as the actual ones. Even when showing the same part, the mutual dimensions and ratios may be different according to the drawings.

[0023] In the present specification and each drawing, the same reference numerals are given to the same elements as those described in the drawings already shown, and the detailed description thereof will be appropriately omitted.

[0024] (First embodiment)

[0025] Figure 1 (a) and Figure 1 (b) is a schematic diagram illustrating the magnetic head according to the first embodiment.

[0026] Figure 1 (a) is a cross-sectional view. Figure 1 (b) is from Figure 1 (a) Plan view as viewed from the arrow AR1.

[0027] Figure 2 This is a schematic cross-sectional view illustrating the magnetic recording device according to the first embodiment.

[0028] like Figure 2 As shown, the magnetic recording device 210 of the embodiment includes a magnetic head 110 and a circuit 20D. The magnetic recording device 210 may also include a magnetic recording medium 80. In the magnetic recording device 210, at least a recording operation is performed. In the recording operation, information is recorded on the magnetic recording medium 80 using the magnetic head 110.

[0029] The magnetic head 110 includes a recording unit 60. As described later, the magnetic head 110 may include a reproducing unit. The recording unit 60 includes a first magnetic pole 31, a second magnetic pole 32, and a laminate 20. The laminate 20 is provided between the first magnetic pole 31 and the second magnetic pole 32.

[0030] 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 main magnetic pole. The second magnetic pole 32 is, for example, a tail shield. Alternatively, the first magnetic pole 31 is a tail shield and the second magnetic pole 32 is a main magnetic pole.

[0031] The direction from the magnetic recording medium 80 to the magnetic head 110 is referred to as the Z-axis direction. A direction perpendicular to the Z-axis direction is referred to as the X-axis direction. The direction perpendicular to the Z-axis direction and the X-axis direction is referred to as the Y-axis direction. The Z-axis direction corresponds to, for example, the height direction. The X-axis direction corresponds to, for example, the along-track direction. The Y-axis direction corresponds to, for example, the through-track direction. Along the along-track direction, the magnetic recording medium 80 and the magnetic head 110 move relative to each other. At a desired position of the magnetic recording medium 80, a magnetic field (recording magnetic field) generated from the magnetic head 110 is applied. The magnetization at the desired position of the magnetic recording medium 80 is controlled to a direction corresponding to the recording magnetic field. Thus, information is recorded on the magnetic recording medium 80.

[0032] The direction from the first magnetic pole 31 to the second magnetic pole 32 is referred to as the first direction D1. The first direction D1 is substantially along the X-axis direction. In the embodiment, the first direction D1 may be inclined at a small angle with respect to the X-axis direction.

[0033] like Figure 2 As shown, a coil 30c is provided. In this example, a portion of the coil 30c is located 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, the first magnetic pole 31 is located between the shield 33 and the second magnetic pole 32. Another portion of the coil 30c is located between the shield 33 and the first magnetic pole 31. An insulating portion 30i is provided between these multiple elements. The shield 33 is, for example, a leading shield. The magnetic head 110 may also include a side shield (not shown).

[0034] like Figure 2As shown in FIG. 1 , a recording current Iw is supplied from the recording circuit 30D to the coil 30c. A recording magnetic field corresponding to the recording current Iw is applied from the first magnetic pole 31 to the magnetic recording medium 80.

[0035] like Figure 2 As shown, the first magnetic pole 31 includes a medium facing surface 30F. The medium facing surface 30F is, for example, an ABS (Air Bearing Surface). The medium facing surface 30F faces, for example, the magnetic recording medium 80. The medium facing surface 30F is, for example, along the XY plane.

[0036] like Figure 2 As shown, the circuit 20D is electrically connected to the laminate 20. In this example, the laminate 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 T1 and a second terminal T2. The first terminal T1 is electrically connected to the laminate 20 via the first wiring W1 and the first magnetic pole 31. The second terminal T2 is electrically connected to the laminate 20 via the second wiring W2 and the second magnetic pole 32. For example, a current (e.g., a direct current) is supplied to the laminate 20 from the circuit 20D.

[0037] like Figure 1 (a) and Figure 1 As shown in (b), the stacked body 20 includes a first magnetic layer 21, a second magnetic layer 22, a third magnetic layer 23, a fourth magnetic layer 24, a first non-magnetic layer 41, a second non-magnetic layer 42, a third non-magnetic layer 43, a fourth non-magnetic layer 44 and a fifth non-magnetic layer 45. Figure 1 (a) and Figure 1 In (b), the insulating portion 30i is omitted.

[0038] The first magnetic layer 21 is provided between the first magnetic pole 31 and the second magnetic pole 32. The second magnetic layer 22 is provided between the second magnetic pole 32 and the first magnetic layer 21. The third magnetic layer 23 is provided between the second magnetic pole 32 and the second magnetic layer 22. The fourth magnetic layer 24 is provided between the second magnetic pole 32 and the third magnetic layer 23. The first non-magnetic layer 41 is provided between the first magnetic layer 21 and the first magnetic pole 31. The second non-magnetic layer 42 is provided between the second magnetic layer 22 and the first magnetic layer 21. The third non-magnetic layer 43 is provided between the third magnetic layer 23 and the second magnetic layer 22. The fourth non-magnetic layer 44 is provided between the fourth magnetic layer 24 and the third magnetic layer 23. The fifth non-magnetic layer 45 is provided between the second magnetic pole 32 and the fourth magnetic layer 24.

[0039] For example, the first nonmagnetic layer 41 may be in contact with the first magnetic layer 21 and the first magnetic pole 31. The second nonmagnetic layer 42 may be in contact with the second magnetic layer 22 and the first magnetic layer 21. The third nonmagnetic layer 43 may be in contact with the third magnetic layer 23 and the second magnetic layer 22. The fourth nonmagnetic layer 42 may be in contact with the fourth magnetic layer 24 and the third magnetic layer 23. The fifth nonmagnetic layer 45 may be in contact with the second magnetic pole 32 and the fourth magnetic layer 24.

[0040] The first magnetic layer 21, the second magnetic layer 22, the third magnetic layer 23, and the fourth magnetic layer 24 include a first element, and the first element includes at least one selected from the group consisting of Fe, Co, and Ni. These magnetic layers may include, for example, FeCo alloys or the like.

[0041] The first nonmagnetic layer 41 includes, for example, at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag. The fifth nonmagnetic layer 45 includes, for example, at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W. Thus, in the laminate 20, the first nonmagnetic layer 41 and the fifth nonmagnetic layer 45 are asymmetric.

[0042] In one example, the second nonmagnetic layer 42 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W, and the third nonmagnetic layer 43 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag. In another example, the second nonmagnetic layer 42 includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag, and the third nonmagnetic layer 43 includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W. In this way, in the stack 20, it is better that the second nonmagnetic layer 42 and the third nonmagnetic layer 43 are asymmetric. The fourth nonmagnetic layer 44 includes, for example, at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag.

[0043] like Figure 1 As shown in (b), current ic is supplied to such a laminate 20. Current ic is supplied, for example, from the above-mentioned circuit 20D. Figure 1 As shown in (b), the current ic has a direction from the first magnetic layer 21 to the second magnetic layer 22. Figure 1 As shown in (b), the electron current je accompanying the current ic has a direction from the second magnetic layer 22 to the first magnetic layer 21. The direction of the current ic is the direction from the first magnetic pole 31 to the second magnetic pole 32.

[0044] For example, a current ic above the threshold value flows through the stack 20, whereby the magnetization of the magnetic layer contained in the stack 20 oscillates. The stack 20 functions as an STO (Spin-Torque Oscillator), for example. As the oscillation occurs, an alternating magnetic field (for example, a high-frequency magnetic field) is generated from the stack 20. The alternating magnetic field generated in the stack 20 is applied to the magnetic recording medium 80 to assist writing to the magnetic recording medium 80. For example, MAMR (Microwave Assisted Magnetic Recording) can be implemented.

[0045] In the magnetic head 110, the first magnetic layer 21 and the third magnetic layer 23 function as, for example, an oscillation layer. For example, the magnetization of the first magnetic layer 21 and the magnetization of the third magnetic layer 23 rotate. The second magnetic layer 22 and the fourth magnetic layer 24 function as, for example, a spin injection layer. In one example, spins are injected from the second magnetic layer 22 and the fourth magnetic layer 24 into the third magnetic layer 23. In another example, spins are injected from the second magnetic layer 22 into the first magnetic layer 21, and spins are injected from the fourth magnetic layer 24 into the third magnetic layer 23.

[0046] like Figure 1 As shown in (b), the thickness of the first magnetic layer 21 along the first direction D1 (the direction from the first magnetic pole 31 to the second magnetic pole 32) is referred to as the first thickness t1. The thickness of the second magnetic layer 22 along the first direction D1 is referred to as the second thickness t2. The thickness of the third magnetic layer 22 along the first direction D1 is referred to as the third thickness t3. The thickness of the fourth magnetic layer 24 along the first direction D1 is referred to as the fourth thickness t4. In the embodiment, the difference between the third thickness t3 and the first thickness t1 is small. For example, the third thickness t3 is greater than 0.5 times and less than 1.5 times the first thickness t1. As a result, as described later, oscillation is easily obtained.

[0047] The thickness of the first non-magnetic layer 41 along the first direction D1 is taken as thickness t41. The thickness of the second non-magnetic layer 42 along the first direction D1 is taken as thickness t42. The thickness of the third non-magnetic layer 43 along the first direction D1 is taken as thickness t43. The thickness of the fourth non-magnetic layer 44 along the first direction D1 is taken as thickness t44. The thickness of the fifth non-magnetic layer 45 along the first direction D1 is taken as thickness t45. These thicknesses are, for example, greater than 0.5 nm and less than 6 nm. By making these thicknesses greater than 0.5 nm, it is easy to reduce magnetic coupling, for example. For example, it is easy to obtain high oscillation strength. By making these thicknesses less than 6 nm, it is possible to suppress the thickness of the stack 20, for example. For example, it is possible to reduce the distance (recording gap) between the first magnetic pole 31 and the second magnetic pole 32. Thus, it is easy to obtain high recording density.

[0048] Next, an example of the simulation result of the oscillation behavior in the stacked body 20 will be described. In the first model and the second model of the simulation, Figure 1 (b) The first magnetic pole 31, the second magnetic pole 32, the first to fourth magnetic layers 21 to 24 and the first to fifth non-magnetic layers 41 to 45 are provided. As the physical property values ​​of the first magnetic layer 21 and the third magnetic layer 23, Fe 70 Co 30 Physical property values ​​of the alloy. As the physical property values ​​of the second magnetic layer 22 and the fourth magnetic layer 24, the physical property values ​​of the FeNi alloy are used. In this example, the FeNi alloy is Fe 78 Ni 22 . The first thickness t1 is 6.5nm. The second thickness t2 is 3nm. The third thickness t3 is 6.5nm. The fourth thickness t4 is 3nm. Thicknesses t41 to t45 are 2nm. In the first model, the physical property values ​​of Cu are used as the physical property values ​​of the first non-magnetic layer 41, the third non-magnetic layer 43, and the fourth non-magnetic layer 44. The physical property values ​​of Ta are used as the physical property values ​​of the second non-magnetic layer 42 and the fifth non-magnetic layer 45. In the second model, the physical property values ​​of Cu are used as the physical property values ​​of the first non-magnetic layer 41, the second non-magnetic layer 42, and the fourth non-magnetic layer 44. The physical property values ​​of Ta are used as the physical property values ​​of the third non-magnetic layer 43 and the fifth non-magnetic layer 45.

[0049] In the third model of the simulation, the second magnetic layer 22 and the third non-magnetic layer 43 are not provided, and the second non-magnetic layer 42 is in contact with the third magnetic layer 23. The other configurations in the third model are the same as those in the first model. Figure 1 (b) Oscillation characteristics of magnetization at the illustrated current ic.

[0050] Figure 3 is a graph illustrating the characteristics of the magnetic head.

[0051] Figure 3 The horizontal axis is the current ic (relative value). The vertical axis is the oscillation intensity OS. The oscillation intensity OS is the sum of the product of the amplitude of the oscillation of the magnetization of the first magnetic layer 21 and the first thickness t1 and the product of the amplitude of the oscillation of the magnetization of the third magnetic layer 23 and the third thickness t3. When the oscillation intensity OS is high, for example, it is easy to increase the recording density using MAMR.

[0052] like Figure 3As shown, in the region where the current ic is small, the oscillation intensity OS of the first model MD1 and the oscillation intensity OS of the second model MD2 are higher than the oscillation intensity OS of the third model MD3. It can be seen that a high oscillation intensity OS is obtained by including the first to fourth magnetic layers 21 to 24. This is considered to be because the addition of the second magnetic layer 22 increases the spin injected into the oscillation layer (i.e., the first magnetic layer 21 or the third magnetic layer 23).

[0053] According to the embodiment, for example, a high oscillation strength OS is obtained. A more stable oscillation is obtained. According to the embodiment, a stable MAMR can be implemented. A magnetic head capable of improving recording density can be provided.

[0054] Figure 4 (a)~ Figure 4 (d) is a graph illustrating the characteristics of the magnetic head.

[0055] Figure 4 The horizontal axis of (a) is the first thickness t1. Figure 4 In (a), the second thickness t2 is 3 nm, the third thickness t3 is 10 nm, and the fourth thickness t4 is 1 nm. Figure 4 The horizontal axis of (b) is the second thickness t2. Figure 4 In (b), the first thickness t1 is 6 nm, the third thickness t3 is 6 nm, and the fourth thickness t4 is 1 nm. Figure 4 The horizontal axis of (c) is the third thickness t3. Figure 4 In (c), the first thickness t1 is 10 nm, the second thickness t2 is 3 nm, and the fourth thickness t4 is 1 nm. Figure 4 The horizontal axis of (d) is the fourth thickness t4. Figure 4 In (d), the first thickness t1 is 8 nm, the second thickness t2 is 8 nm, and the third thickness t3 is 5 nm. In these figures, the current ic supplied to the stacked body 20 is 1.2×10 8 A / cm 2 The vertical axis of these graphs is the oscillation intensity OS.

[0056] like Figure 4 As shown in (a), the first thickness t1 is preferably not less than 5 nm and not more than 15 nm. Thus, a high oscillation strength OS is obtained.

[0057] like Figure 4As shown in (b), when the second thickness t2 is in the range of 1 nm to 10 nm, the oscillation intensity OS does not substantially change. For example, the second thickness t2 is, for example, greater than 1 nm and less than 10 nm. The thinner the second thickness t2 is, the better. For example, the second thickness t2 may also be, for example, greater than 1 nm and less than 8 nm. By making the second thickness t2 thin, the thickness of the stack 20 becomes thinner. For example, the recording gap can be reduced. Thus, a high recording density can be easily obtained. For example, the second thickness t2 may also be less than 3 nm. For example, the second thickness t2 may also be less than 2 nm.

[0058] like Figure 4 As shown in (c), the third thickness t3 is preferably not less than 5 nm and not more than 15 nm. Thus, a high oscillation strength OS is obtained.

[0059] like Figure 4 As shown in (d), the fourth thickness t4 is preferably 5 nm or less. This provides a high oscillation strength OS. The fourth thickness t4 is, for example, 1 nm or more and 5 nm or less.

[0060] Figure 5 (a)~ Figure 5 (c) is a graph illustrating the characteristics of the magnetic head.

[0061] Figure 5 The horizontal axis of (a) is the ratio R21. The ratio R21 is the ratio of the second thickness t2 to the first thickness t1. Figure 5 The horizontal axis of (b) is the ratio R31. The ratio R31 is the ratio of the third thickness t3 to the first thickness t1. Figure 5 The horizontal axis of (c) is the ratio R41. The ratio R41 is the ratio of the fourth thickness t4 to the first thickness t1. Figure 5 In (a), the ratio R31 is 1 and the ratio R41 is 0.17. Figure 5 In (b), the ratio R21 is 0.3 and the ratio R41 is 0.1. Figure 5 In (c), the ratio R21 is 0.7 and the ratio R31 is 1.

[0062] like Figure 5 As shown in (a), within the range of 0.2 to 1.5 of the ratio R21, the oscillation intensity OS does not substantially change. The ratio R21 is preferably lower. It is easy to reduce the recording gap. For example, the second thickness t2 is preferably smaller than the first thickness t1. For example, the second thickness t2 is preferably less than 0.75 times the first thickness t1. The second thickness t2 may also be less than 0.5 times the first thickness t1. For example, it is easy to reduce the recording gap. For example, it is easy to obtain a high recording density.

[0063] like Figure 5As shown in (b), the ratio R31 is preferably close to 1. Thus, a high oscillation strength OS is obtained. For example, the third thickness t3 is preferably 0.5 times or more and 1.5 times or less of the first thickness t1. For example, the third thickness t3 may also be 0.8 times or more and 1.25 times or less of the first thickness t1. A high oscillation strength OS is obtained.

[0064] like Figure 5 As shown in (c), it is preferably lower than R41. Thus, a high oscillation strength OS is obtained. For example, the fourth thickness t4 is preferably smaller than the first thickness t1. For example, the fourth thickness t4 is preferably less than 0.7 times the first thickness t1. For example, the fourth thickness t4 may also be less than 0.5 times the first thickness t1. A high oscillation strength OS is obtained.

[0065] Figure 6 (a)~ Figure 6 (c) is a graph illustrating the characteristics of the magnetic head.

[0066] Figure 6 The horizontal axis of (a) is the ratio R23. The ratio R23 is the ratio of the second thickness t2 to the third thickness t3. Figure 6 The horizontal axis of (b) is the ratio R43. The ratio R43 is the ratio of the fourth thickness t4 to the third thickness t3. Figure 6 The horizontal axis of (c) is the ratio R42. The ratio R42 is the ratio of the fourth thickness t4 to the second thickness t2. Figure 6 In (a), the ratio R31 is 1 and the ratio R41 is 0.17. Figure 6 In (b), the ratio R21 is 0.5 and the ratio R31 is 0.7. Figure 6 In (c), the ratio R31 is 1 and the ratio R21 is 0.38.

[0067] like Figure 6 As shown in (a), within the range of 0.2 to 1.5 of the ratio R23, the oscillation intensity OS does not substantially change. The ratio R23 is preferably lower. It is easy to reduce the recording gap. For example, the second thickness t2 is preferably, for example, smaller than the third thickness t3. For example, the second thickness t2 is preferably, for example, less than 0.75 times the third thickness t3. The second thickness t2 may also be, for example, less than 0.5 times the third thickness t3. For example, it is easy to reduce the recording gap. For example, it is easy to obtain a high recording density.

[0068] like Figure 6 As shown in (b), it is preferably lower than R43. Thus, a high oscillation strength OS is obtained. For example, the fourth thickness t4 is preferably smaller than the third thickness t3. For example, the fourth thickness t4 is preferably less than 0.7 times the third thickness t3. For example, the fourth thickness t4 may also be less than 0.5 times the third thickness t3. A high oscillation strength OS is obtained.

[0069] like Figure 6 As shown in (c), it is preferably lower than R42. Thus, a high oscillation strength OS is obtained. For example, the fourth thickness t4 is preferably 1.5 times or less of the second thickness t2. For example, the fourth thickness t4 may also be less than the second thickness t2. A high oscillation strength OS is obtained.

[0070] As described above, the first magnetic layer 21, the second magnetic layer 22, the third magnetic layer 23, and the fourth magnetic layer 24 include a first element including at least one selected from the group consisting of Fe, Co, and Ni. In an embodiment, for example, the first magnetic layer 21, the second magnetic layer 22, the third magnetic layer 23, and the fourth magnetic layer 24 do not substantially include a second element including at least one selected from the group consisting of Cr, V, Mn, Ti, and Sc. Alternatively, the concentration of the second element in the first magnetic layer 21, the second magnetic layer 22, the third magnetic layer 23, and the fourth magnetic layer 24 is less than 10 atm%. For example, the first to fourth magnetic layers 21 to 24 have, for example, positive polarization. In such a magnetic layer, stable oscillation is easily obtained.

[0071] Figure 4 (a)~ Figure 4 (d) Figure 5 (a)~ Figure 5 (c) and Figure 6 (a)~ Figure 6 (c) is an example of the simulation result of the characteristics in the first model MD1. In the second model MD2, the same tendency as above is obtained.

[0072] In an embodiment, the first magnetic pole 31 may include a plurality of magnetic regions arranged along the X-axis direction. The second magnetic pole 32 may include a plurality of magnetic regions arranged along the X-axis direction. The boundaries between the plurality of magnetic regions may be clear or unclear. For example, the plurality of magnetic regions are continuous.

[0073] Hereinafter, an example of a magnetic head and a magnetic recording medium 80 included in the magnetic recording device 210 according to the embodiment will be described.

[0074] Figure 7 It is a schematic cross-sectional view illustrating a magnetic head according to the embodiment.

[0075] like Figure 7 As shown, in the magnetic head of the embodiment (for example, the magnetic head 110), the first direction D1 from the first magnetic pole 31 to the second magnetic pole 32 may also be relative to the X-axis direction. The first direction D1 corresponds to the stacking direction of the stacked body 20. The X-axis direction is along the medium-opposing surface 30F. The absolute value of the angle between the first direction D1 and the medium-opposing surface 30F is set to angle θ1. The angle θ1 is, for example, greater than 15 degrees and less than 30 degrees. The angle θ1 may also be 0 degrees.

[0076] When the first direction D1 is inclined relative to the X-axis direction, the thickness of the layer corresponds to the length along the first direction D1. The configuration in which the first direction D1 is inclined relative to the X-axis direction can be applied to any magnetic head of the embodiment. For example, the interface between the first magnetic pole 31 and the stacked body 20, and the interface between the stacked body 20 and the second magnetic pole 32 can be inclined relative to the X-axis direction.

[0077] Hereinafter, an example of a magnetic head and a magnetic recording medium 80 included in the magnetic recording device 210 according to the embodiment will be described.

[0078] Figure 8 It is a schematic perspective view illustrating a magnetic recording device according to an embodiment.

[0079] like Figure 8 As shown, the magnetic head (e.g., magnetic head 110) of the embodiment is used together with the magnetic recording medium 80. In this example, the magnetic head 110 includes a recording unit 60 and a reproducing unit 70. Information is recorded on the magnetic recording medium 80 by the recording unit 60 of the magnetic head 110. Information recorded on the magnetic recording medium 80 is reproduced by the reproducing unit 70.

[0080] The magnetic recording medium 80 includes, for example, a dielectric substrate 82 and a magnetic recording layer 81 provided on the dielectric substrate 82. The magnetization 83 of the magnetic recording layer 81 is controlled by the recording unit 60.

[0081] The reproduction unit 70 includes, for example, a first reproduction magnetic shield 72a, a second reproduction magnetic shield 72b, and a magnetic reproduction element 71. The magnetic reproduction element 71 is provided between the first reproduction magnetic shield 72a and the second reproduction magnetic shield 72b. The magnetic reproduction element 71 can output a signal corresponding to the magnetization 83 of the magnetic recording layer 81.

[0082] like Figure 8 As shown, the magnetic recording medium 80 moves relative to the magnetic head 110 in the direction of the medium moving direction 85. The magnetic head 110 controls 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.

[0083] Fig. 9 This is a schematic perspective view illustrating a part of the magnetic recording device according to the embodiment.

[0084] Fig. 9 A head slider is illustrated.

[0085] The magnetic head 110 is provided on a head slider 159. The head slider 159 is made of, for example, Al2O3 / TiC, etc. The head slider 159 moves relative to the magnetic recording medium while floating or contacting the magnetic recording medium.

[0086] The head slider 159 has, for example, an air inlet side 159A and an air outlet side 159B. The magnetic head 110 is disposed on the side of the air outlet side 159B of the head slider 159. Thus, the magnetic head 110 moves relative to the magnetic recording medium while floating or contacting the magnetic recording medium.

[0087] Fig.10 It is a schematic perspective view illustrating a magnetic recording device according to an embodiment.

[0088] like Fig.10 As shown, in the magnetic recording device 150 of the embodiment, a rotary actuator is used. The recording medium disk 180 is installed on the spindle motor 180M. The recording medium disk 180 is rotated in the direction of the arrow AR by the spindle motor 180M. The spindle motor 180M responds to the control signal from the drive device control unit. The magnetic recording device 150 of this embodiment may have a plurality of 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). The recording medium 181 is, for example, a non-volatile memory such as a flash memory. For example, the magnetic recording device 150 may be a hybrid HDD (Hard Disk Drive).

[0089] The head slider 159 performs recording and reproduction of information recorded on the recording medium disk 180. The head slider 159 is provided at the top end of the thin film suspension 154. The magnetic head of the embodiment is provided near the top end of the head slider 159.

[0090] When the recording medium disk 180 rotates, the pressing force generated by the suspension 154 and the pressure generated on the medium facing surface (ABS) of the head slider 159 are balanced. The distance between the medium facing surface of the head slider 159 and the surface of the recording medium disk 180 becomes a predetermined floating amount. In the embodiment, the head slider 159 may also contact the recording medium disk 180. For example, a contact travel type may be applied.

[0091] The suspension 154 is connected to one end of an arm 155 (e.g., an actuator arm). The arm 155 has, for example, a coil frame portion, etc. The coil frame portion holds a driving coil. A voice coil motor 156 is provided at the other end of the arm 155. The voice coil motor 156 is a type of linear motor. The voice coil motor 156 includes, for example, a driving coil and a magnetic circuit. The driving coil is wound around the coil frame portion of the arm 155. The magnetic circuit includes a permanent magnet and a relative magnetic yoke. A driving coil is provided between the permanent magnet and the relative magnetic 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.

[0092] The arm 155 is held by a ball bearing. The ball bearings are provided at two locations, upper and lower, of the bearing portion 157. The arm 155 can be rotated and slid by the voice coil motor 156. The magnetic head can be moved to any position of the recording medium disk 180.

[0093] Fig.11 (a) and Fig.11 (b) is a schematic perspective view illustrating a part of the magnetic recording device according to the embodiment.

[0094] Fig.11 (a) illustrates a partial structure of the magnetic recording device and is an enlarged perspective view of the head stack assembly 160 . Fig.11 (b) is a perspective view illustrating a head assembly (head gimbal assembly: HGA) 158 which is a part of the head stack assembly 160 .

[0095] like Fig.11 As shown in (a), the head stack assembly 160 includes a bearing portion 157, a head gimbal assembly 158, and a bracket 161. The head gimbal assembly 158 extends from the bearing portion 157. The bracket 161 extends from the bearing portion 157. The direction in which the bracket 161 extends is opposite to the direction in which the head gimbal assembly 158 extends. The bracket 161 supports the coil 162 of the voice coil motor 156.

[0096] like Fig.11 As shown in (b), the head gimbal assembly 158 has an arm 155 extending from a bearing portion 157 and a suspension 154 extending from the arm 155.

[0097] A head slider 159 is provided at the top end of the suspension 154. The head slider 159 is provided with the magnetic head of the embodiment.

[0098] The head assembly (head gimbal assembly) 158 of the embodiment includes the magnetic head of the embodiment, a head slider 159 provided with the magnetic head, a suspension 154, and an 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.

[0099] The suspension 154 may include, for example, a wire for recording and reproducing a signal (not shown). The suspension 154 may include, for example, a wire for a heater for adjusting the floating amount (not shown). The suspension 154 may also include, for example, a wire for a spin-transfer torque oscillator (not shown). These wires are electrically connected to a plurality of electrodes provided on the magnetic head.

[0100] The magnetic recording device 150 includes a signal processing unit 190. The signal processing unit 190 uses a magnetic head to record and reproduce signals on a magnetic recording medium. The input and output lines of the signal processing unit 190 are connected to, for example, electrode pads of the head gimbal assembly 158 and are electrically connected to the magnetic head.

[0101] The magnetic recording device 150 of the embodiment includes a magnetic recording medium, a magnetic head of the embodiment, a movable part, a position control part and a signal processing part. The movable part can move relative to each other in a state where the magnetic recording medium and the magnetic head are separated or in contact. The position control part positions the magnetic head at a predetermined recording position of the magnetic recording medium. The signal processing part performs recording and reproduction of signals to the magnetic recording medium using the magnetic head.

[0102] For example, as the magnetic recording medium, a recording medium disk 180 is used. The movable portion includes, for example, a head slider 159. The position control portion includes, for example, a head gimbal assembly 158.

[0103] The implementation method may include the following technical solutions.

[0104] (Technical Solution 1)

[0105] A magnetic head comprises a first magnetic pole, a second magnetic pole, and a stacked body disposed between the first magnetic pole and the second magnetic pole;

[0106] The laminate includes a first magnetic layer, a second magnetic layer disposed between the second magnetic pole and the first magnetic layer, a third magnetic layer disposed between the second magnetic pole and the second magnetic layer, a fourth magnetic layer disposed between the second magnetic pole and the third magnetic layer, a first non-magnetic layer disposed between the first magnetic layer and the first magnetic pole, a second non-magnetic layer disposed between the second magnetic layer and the first magnetic layer, a third non-magnetic layer disposed between the third magnetic layer and the second magnetic layer, a fourth non-magnetic layer disposed between the fourth magnetic layer and the third magnetic layer, and a fifth non-magnetic layer disposed between the second magnetic pole and the fourth magnetic layer;

[0107] The second non-magnetic layer is in contact with the second magnetic layer and the first magnetic layer;

[0108] The third non-magnetic layer is in contact with the third magnetic layer and the second magnetic layer;

[0109] The fourth non-magnetic layer is in contact with the fourth magnetic layer and the third magnetic layer.

[0110] (Technical Solution 2)

[0111] A magnetic head as described in technical solution 1, wherein:

[0112] The first non-magnetic layer is in contact with the first magnetic layer and the first magnetic pole.

[0113] (Technical Solution 3)

[0114] A magnetic head as described in technical solution 2, wherein:

[0115] The fifth non-magnetic layer is in contact with the second magnetic pole and the fourth magnetic layer.

[0116] (Technical Solution 4)

[0117] A magnetic head as described in any one of technical solutions 1 to 3, wherein:

[0118] The fifth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

[0119] (Technical Solution 5)

[0120] A magnetic head as described in technical solution 4, wherein:

[0121] The first nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

[0122] (Technical Solution 6)

[0123] A magnetic head as described in technical solution 3 or 4, wherein:

[0124] The fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

[0125] (Technical Solution 7)

[0126] A magnetic head as described in any one of technical solutions 1 to 6, wherein:

[0127] The second non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W, and the third non-magnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag; or

[0128] The second non-magnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag, and the third non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W.

[0129] (Technical Solution 8)

[0130] A magnetic head as described in any one of technical solutions 1 to 7, wherein:

[0131] A third thickness of the third magnetic layer along a first direction from the first magnetic pole toward the second magnetic pole is not less than 0.5 times and not more than 1.5 times the first thickness of the first magnetic layer along the first direction.

[0132] (Technical Solution 9)

[0133] A magnetic head as described in technical solution 8, wherein:

[0134] The third thickness is not less than 0.8 times and not more than 1.25 times the first thickness.

[0135] (Technical Solution 10)

[0136] A magnetic head as described in technical solution 8 or 9, wherein:

[0137] A fourth thickness of the fourth magnetic layer along the first direction is smaller than the first thickness;

[0138] The fourth thickness is smaller than the third thickness.

[0139] (Technical Solution 11)

[0140] A magnetic head as described in technical solution 8 or 9, wherein:

[0141] A fourth thickness of the fourth magnetic layer along the first direction is less than or equal to 0.7 times the first thickness;

[0142] The fourth thickness is not more than 0.7 times the third thickness.

[0143] (Technical Solution 12)

[0144] A magnetic head as described in any one of technical solutions 8 to 11, wherein

[0145] A second thickness of the second magnetic layer along the first direction is smaller than the first thickness;

[0146] The second thickness is smaller than the third thickness.

[0147] (Technical Solution 13)

[0148] A magnetic head as described in any one of technical solutions 8 to 11, wherein

[0149] A second thickness of the second magnetic layer along the first direction is less than or equal to 0.75 times the first thickness;

[0150] The second thickness is not more than 0.75 times the third thickness.

[0151] (Technical Solution 14)

[0152] A magnetic head as described in any one of technical solutions 8 to 9, wherein:

[0153] A fourth thickness of the fourth magnetic layer along the first direction is 1.5 times or less of a second thickness of the second magnetic layer along the first direction.

[0154] (Technical Solution 15)

[0155] A magnetic head as described in any one of technical solutions 8 to 9, wherein:

[0156] A fourth thickness of the fourth magnetic layer along the first direction is less than or equal to a second thickness of the second magnetic layer along the first direction.

[0157] (Technical Solution 16)

[0158] A magnetic head as described in any one of technical solutions 8 to 15, wherein

[0159] A thickness of the second magnetic layer along the first direction is greater than or equal to 1 nm and less than or equal to 8 nm.

[0160] (Technical Solution 17)

[0161] A magnetic head as described in any one of technical solutions 8 to 16, wherein

[0162] A thickness of the fourth magnetic layer along the first direction is greater than or equal to 1 nm and less than or equal to 5 nm.

[0163] (Technical Solution 18)

[0164] A magnetic head as described in any one of technical solutions 8 to 17, wherein:

[0165] The first thickness is greater than or equal to 5 nm and less than or equal to 15 nm;

[0166] The third thickness is greater than or equal to 5 nm and less than or equal to 15 nm.

[0167] (Technical Solution 19)

[0168] A magnetic recording device, comprising a magnetic head and a circuit according to any one of technical solutions 1 to 18;

[0169] The circuit is capable of supplying current to the stack;

[0170] The current has a direction from the first magnetic layer to the second magnetic layer.

[0171] (Technical Solution 20)

[0172] A magnetic recording device as described in technical solution 19, wherein:

[0173] When the electric circuit supplies the current to the stacked body, an alternating magnetic field is generated from the stacked body.

[0174] According to the embodiment, it is possible to provide a magnetic head and a magnetic recording device capable of improving recording density.

[0175] In the present specification, “perpendicular” and “parallel” do not necessarily mean strictly perpendicular or strictly parallel, but also include, for example, deviations in the manufacturing process, as long as they are substantially perpendicular or substantially parallel.

[0176] The embodiments of the present invention are described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, the specific configuration of each element such as the magnetic pole, laminate, magnetic layer, non-magnetic layer and wiring contained in the magnetic head is also included in the scope of the present invention as long as those skilled in the art can obtain the same effect by appropriately selecting from the known range to implement the present invention in the same manner.

[0177] Configurations in which two or more elements of the specific examples are combined within a technically possible range are also included in the scope of the present invention as long as they include the gist of the present invention.

[0178] In addition, as an embodiment of the present invention, all magnetic heads and magnetic recording devices that can be implemented by technicians in this field through appropriate design changes based on the above-mentioned magnetic heads and magnetic recording devices also belong to the scope of the present invention as long as they include the gist of the present invention.

[0179] Furthermore, within the scope of the concept of the present invention, those skilled in the art can conceive of various changes and modifications, and it should be understood that these changes and modifications also belong to the scope of the present invention.

[0180] Several embodiments of the present invention have been described, but these embodiments are merely presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their variations are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope of their equivalents.

Claims

1. A magnetic head comprising a first magnetic pole, a second magnetic pole, and a stacked body disposed between the first magnetic pole and the second magnetic pole; The laminate includes a first magnetic layer, a second magnetic layer disposed between the second magnetic pole and the first magnetic layer, a third magnetic layer disposed between the second magnetic pole and the second magnetic layer, a fourth magnetic layer disposed between the second magnetic pole and the third magnetic layer, a first non-magnetic layer disposed between the first magnetic layer and the first magnetic pole, a second non-magnetic layer disposed between the second magnetic layer and the first magnetic layer, a third non-magnetic layer disposed between the third magnetic layer and the second magnetic layer, a fourth non-magnetic layer disposed between the fourth magnetic layer and the third magnetic layer, and a fifth non-magnetic layer disposed between the second magnetic pole and the fourth magnetic layer; The second non-magnetic layer is in contact with the second magnetic layer and the first magnetic layer; The third non-magnetic layer is in contact with the third magnetic layer and the second magnetic layer; The fourth non-magnetic layer is in contact with the fourth magnetic layer and the third magnetic layer; A third thickness of the third magnetic layer along a first direction from the first magnetic pole toward the second magnetic pole is not less than 0.5 times and not more than 1.5 times the first thickness of the first magnetic layer along the first direction.

2. The magnetic head according to claim 1, The first non-magnetic layer is in contact with the first magnetic layer and the first magnetic pole; The fifth non-magnetic layer is in contact with the second magnetic pole and the fourth magnetic layer.

3. The magnetic head according to claim 1, The fifth nonmagnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt, and W.

4. The magnetic head according to claim 3, The first nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

5. The magnetic head according to claim 3, The fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

6. The magnetic head according to claim 1, A fourth thickness of the fourth magnetic layer along the first direction is less than or equal to 0.7 times the first thickness; The fourth thickness is not more than 0.7 times the third thickness.

7. The magnetic head according to claim 1, A second thickness of the second magnetic layer along the first direction is less than or equal to 0.75 times the first thickness; The second thickness is not more than 0.75 times the third thickness.

8. The magnetic head according to claim 1, A fourth thickness of the fourth magnetic layer along the first direction is 1.5 times or less of a second thickness of the second magnetic layer along the first direction.

9. The magnetic head according to claim 1, The second non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W, The third non-magnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag. The fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

10. The magnetic head according to claim 1, The second non-magnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag. The third non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W. The fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

11. A magnetic head comprising a first magnetic pole, a second magnetic pole, and a stacked body disposed between the first magnetic pole and the second magnetic pole; The laminate includes a first magnetic layer, a second magnetic layer disposed between the second magnetic pole and the first magnetic layer, a third magnetic layer disposed between the second magnetic pole and the second magnetic layer, a fourth magnetic layer disposed between the second magnetic pole and the third magnetic layer, a first non-magnetic layer disposed between the first magnetic layer and the first magnetic pole, a second non-magnetic layer disposed between the second magnetic layer and the first magnetic layer, a third non-magnetic layer disposed between the third magnetic layer and the second magnetic layer, a fourth non-magnetic layer disposed between the fourth magnetic layer and the third magnetic layer, and a fifth non-magnetic layer disposed between the second magnetic pole and the fourth magnetic layer; The second non-magnetic layer is in contact with the second magnetic layer and the first magnetic layer; The third non-magnetic layer is in contact with the third magnetic layer and the second magnetic layer; The fourth non-magnetic layer is in contact with the fourth magnetic layer and the third magnetic layer; The second non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W; The third non-magnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag; The fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

12. A magnetic head comprising a first magnetic pole, a second magnetic pole, and a stacked body disposed between the first magnetic pole and the second magnetic pole; The laminate includes a first magnetic layer, a second magnetic layer disposed between the second magnetic pole and the first magnetic layer, a third magnetic layer disposed between the second magnetic pole and the second magnetic layer, a fourth magnetic layer disposed between the second magnetic pole and the third magnetic layer, a first non-magnetic layer disposed between the first magnetic layer and the first magnetic pole, a second non-magnetic layer disposed between the second magnetic layer and the first magnetic layer, a third non-magnetic layer disposed between the third magnetic layer and the second magnetic layer, a fourth non-magnetic layer disposed between the fourth magnetic layer and the third magnetic layer, and a fifth non-magnetic layer disposed between the second magnetic pole and the fourth magnetic layer; The second non-magnetic layer is in contact with the second magnetic layer and the first magnetic layer; The third non-magnetic layer is in contact with the third magnetic layer and the second magnetic layer; The fourth non-magnetic layer is in contact with the fourth magnetic layer and the third magnetic layer; The second non-magnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V and Ag; The third non-magnetic layer includes at least one selected from the group consisting of Ru, Ir, Ta, Rh, Pd, Pt and W; The fourth nonmagnetic layer includes at least one selected from the group consisting of Cu, Au, Cr, Al, V, and Ag.

13. A magnetic recording device comprising the magnetic head and the circuit according to claim 1, 11 or 12; The circuit is capable of supplying current to the stack; The current has a direction from the first magnetic layer to the second magnetic layer.

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