JP5468124B2 - Magnetic recording head and magnetic recording apparatus - Google Patents

Description

  The present invention includes a magnetic recording head having a function of recording information by irradiating a magnetic recording medium with a high frequency magnetic field to drive magnetic resonance and inducing magnetization reversal of the recording medium, and the magnetic recording head. The present invention relates to a magnetic recording apparatus.

The amount of information distributed in the form of digital data has increased dramatically as the capabilities of computers in recent years and the speed and capacity of networks have increased. In order to efficiently receive, distribute, and extract such a large amount of information, a storage device that can input and output a large amount of information at high speed is required. In the magnetic disk, as the recording density is increased, a problem that a signal once recorded gradually decreases due to thermal fluctuation has become apparent. This is because the magnetic recording medium is an assembly of magnetic crystallites, and the volume of the crystallites is decreasing. In order to obtain sufficient heat fluctuation stability, the commonly used thermal fluctuation index Kβ (= K _u V / kT; _Ku : magnetic anisotropy, V: particle volume, T: absolute temperature, k: Boltzmann constant) It is believed that there must be more than 70. If K _u and T (material, environment) are constant, magnetization reversal due to thermal fluctuation is more likely to occur in particles with smaller V. As the recording density increases and the recording film volume occupied by 1 bit decreases, V must be lowered, and thermal fluctuation cannot be ignored. Increasing the K _u in order to suppress the thermal fluctuation, it will exceed a recording magnetic field of the magnetization reversal magnetic field necessary for magnetic recording can be generated by the recording head, the recording disabled state.

In order to avoid this problem, Patent Document 1 discloses a microwave assisted magnetic recording (MAMR) technique by Chu Zhu et al. As shown in FIG. 1A, MAMR is a microwave magnetic field from a spin torque oscillator (STO) arranged adjacent to the main magnetic pole in addition to the write magnetic field from the main magnetic pole of the perpendicular magnetic recording head. Is applied to the magnetic recording medium 7 having a large magnetic anisotropy, the recording target region is set in a magnetic resonance state, the magnetization is shaken, and the magnetization reversal magnetic field is lowered to perform recording. Recording to a microwave irradiation region is possible for a magnetic recording medium corresponding to a high recording density exceeding 1 Tbit / in ² , which has been difficult to record with a conventional magnetic head due to insufficient recording magnetic field. The STO transmits the spin torque from the fixed layer 31 to the adjacent high frequency magnetic field generation layer (FGL) 32 through Cu, and rotates the magnetization of the FGL 32 that is the in-plane free layer at a high speed in the plane. Microwave (high frequency magnetic field) is generated.

Since MAMR uses a magnetic resonance phenomenon, an effective microwave magnetic field component is a counterclockwise rotating magnetic field component that has the same rotational direction as the precession of magnetization of the recording medium. On the other hand, as shown in FIG. 1B, the microwave magnetic field from the FGL 32 that is the STO microwave magnetic field generation source is an elliptical rotating magnetic field whose rotation direction depends on the magnetization rotation direction of the FGL. The direction is backward and forward. Therefore, a counterclockwise rotating magnetic field effective for MAMR is created only on one side of the front and rear of the FGL 32. For this reason, it is necessary to reverse the rotation direction of the magnetization of the FGL 32 every time the main magnetic pole polarity is reversed. As disclosed in Patent Document 2 and Patent Document 3, it is practical to reverse the magnetization of the fixed layer serving as a spin torque source according to the main magnetic pole magnetic field H _ext while keeping the STO drive current constant (FIG. 2A and FIG. 2). 2B).

  In this case, since it is considered that the spin torque necessary for FGL driving cannot be obtained during the magnetization reversal of the fixed layer, it is necessary to increase the speed of the fixed layer magnetization reversal. Patent Document 2 discloses a technique for reducing the coercive force of the fixed layer of the STO disclosed in Patent Document 1 and reversing the fixed layer magnetization by the main magnetic pole magnetic field, and a magnetic material having a high magnetic flux density in the vicinity of the fixed layer. A technique for increasing the reversal speed by installing a cable is disclosed. Patent Document 2 discloses a technique in which a part of a main magnetic pole or an auxiliary magnetic pole is substantially a fixed layer. A protrusion (lip) is provided on the main magnetic pole, a high-frequency magnetic field generator is disposed through the spin scattering layer, and a current is applied so that the spin torque acts in a direction to suppress the influence of the magnetic field from the main magnetic pole on the FGL. It is set to flow. With this configuration, it is possible to allow the inflow magnetic field from the main pole to the high-frequency magnetic field generator to be perpendicular to the film surface, and since the main pole is used as a spin source, the maximum high-frequency does not depend on the polarity of the main pole. A high-frequency magnetic field generator driving current capable of obtaining a magnetic field can be set according to a desired frequency.

  Further, by forming an equivalent FGL pair that rotates at high speed while keeping the magnetizations antiparallel to each other, and applying a unidirectional high-frequency magnetic field parallel to the recording medium surface generated from the end face, the efficiency is improved regardless of the FGL rotation direction. Techniques for reversing the medium magnetization well are disclosed in Patent Documents 4 and 5.

US 2008/0019040 A1 JP 2009-070541 A Japanese Patent Application No. 2010-510082 JP 2008-277586 A JP 2008-305486 A

  In microwave assisted recording (MAMR) having a recording density exceeding 1 Tbit per square inch, a magnetic recording medium is irradiated with a strong high-frequency magnetic field on a nanometer-order region to which a write magnetic field from a main pole is applied. Is locally magnetically resonant, and the information is recorded by reducing the magnetization reversal field. Because of the principle of magnetic resonance, only the high-frequency rotating magnetic field component coinciding with the rotation direction of the precession of magnetization in the recording area is effective for medium magnetization reversal. Therefore, in order to obtain a high-frequency magnetic field with high reversal efficiency, it is necessary to reverse the rotation direction of the FGL magnetization when the main magnetic pole polarity is reversed. If the rotation direction of the magnetization of the FGL is not reversed every time the main magnetic pole polarity is reversed, the reversal position of the medium magnetization is shifted before and after the FGL, and the linear recording density cannot be increased.

  In Patent Document 1, since a multi-layer film having high magnetic anisotropy (and relatively low saturation magnetic flux density) such as (Co / Pd) n and (Co / Pt) n is used for the fixed layer of STO, it is stable. It is considered that spin torque is supplied to the FGL. However, since the fixed layer magnetization does not reverse with the reversal of the main magnetic pole polarity, the STO drive current is reversed in order to reverse the rotation direction of the FGL magnetization. In this case, the efficiency of the spin torque changes depending on whether the current is positive or negative, b) the external magnetic field applied to the FGL is not equal, c) the rising angle of the FGL magnetization is different, and d) the STO drive current is the main magnetic pole magnetic field. It is necessary to solve the problem that it is necessary to synchronize, and it is extremely difficult to realize.

In Patent Document 2, a multilayer film such as (Co / Pd) n, (Co / Pt) n having a coercive force lower than the magnetic field from the main pole is used for the fixed layer serving as a spin torque source, and the STO driving current is constant. In this state, the magnetization of the fixed layer is reversed in synchronization with the polarity of the main magnetic pole, and then the rotation direction of the magnetization of the FGL is reversed. The coercive force was low (Co / Pd) n, multilayer film such as (Co / Pt) n tends to saturation magnetic flux density B _s is further lowered, be stacked high B _s material, sufficient fixing The magnetization reversal speed of the layer cannot be obtained. In addition, since the coercive force of the fixed layer is low, there is a problem that when the current is increased to supply a large spin torque to the FGL, the fixed layer magnetization becomes unstable due to the reaction. Furthermore, since these multilayer films have a large damping constant α of magnetization motion of 0.1-0.3, spin is consumed by the spin pumping action, so it is necessary to flow a large amount of current to obtain a high-frequency magnetic field of the same frequency. There is also a problem.

  In Patent Document 3, the protrusion (lip) portion provided on the main magnetic pole is used as a fixed layer, so that the magnetization of the fixed layer is reversed in synchronization with the main magnetic pole polarity while keeping the STO drive current constant. The direction of magnetization rotation is reversed. Since a part of the main magnetic pole or auxiliary magnetic pole is substantially a fixed layer, the magnetization reversal speed is considered to be sufficiently high. However, the magnetization of the fixed layer is likely to fluctuate due to the influence of the magnetization state of the main magnetic pole and the reaction of the spin torque from the FGL, and it is difficult to flow a large STO drive current and increase the oscillation frequency. In these Patent Documents 2 and 3, the magnetization of the magnetic material serving as the spin torque source is reversed in synchronization with the main magnetic pole polarity when the main magnetic pole polarity is reversed. Therefore, the total value of the main magnetic pole polarity reversal time, the fixed layer reversal time, and the FGL stabilization time is required until a stable oscillation state is achieved at the time of reversing the main magnetic pole polarity. There are concerns that cannot be met.

  In Patent Documents 4 and 5, an in-plane linear oscillating magnetic field is generated at the center of the head, and there is no difference in recording characteristics depending on the rotation direction of the FGL. However, at the track end, the influence of the high-frequency magnetic field with phase lag from the FGL end is unavoidable, and the influence of the rotating magnetic field component becomes significant. Therefore, when the track density is increased, the recording characteristics depend on the rotation direction of the FGL. It will change. For this reason, similarly to Patent Documents 2 and 3, it is necessary to reverse the magnetization of the fixed layer in synchronization with the main magnetic pole polarity. The techniques of Patent Documents 4 and 5 also have a problem that the required current is doubled because, in principle, it is necessary to rotate the fixed layer magnetization equivalent to the FGL magnetization at high speed.

In the HDD, the bit length in the track direction is shortened as the surface recording density increases. In magnetic recording exceeding 1 Tbit / in ² , the bit length in the track direction is expected to be 10 nm or less. In this case, when a head-medium relative speed of 20 m / s, which is typically used in current HDDs, is applied, recording is performed at 10/20 = 0.5 n seconds or less per bit. In this case, the information transfer rate is 2 Gbit / s. In the techniques of Patent Documents 2 to 5, it is necessary to reverse the fixed layer magnetization in synchronization with the main magnetic pole polarity. For this reason, even if the inversion time of the fixed layer is 0.2 nsec or less, the FGL magnetization may be separated from the stable oscillation state due to the spin torque transmitted from the fixed layer during this inversion time. Since recovery is considered to take an equivalent amount of time, it is difficult to realize an information transfer rate exceeding 2 Gbit / s.

  An object of the present invention is to provide a magnetic recording suitable for ultra-high density magnetic recording that is highly reliable and results in cost reduction by setting the time from the start of polarity reversal to the steady oscillation state to 0.3 nsec or less. To provide a head and a magnetic recording apparatus.

  The magnetic recording head of the present invention has a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, generates a magnetization reversal magnetic field from the main magnetic pole, and generates a high-frequency magnetic field from the spin torque oscillation element. A magnetic recording head for recording information by reversing the magnetization of a magnetic recording medium. A spin torque oscillation element includes a vertical free layer composed of a magnetic film having a magnetic anisotropy axis in a direction perpendicular to the film surface, and an effective And an in-plane free layer having an easy magnetization surface on the film surface, and a current flows from the in-plane free layer side to the vertical free layer side. The vertical free layer is preferably thinner than the in-plane free layer. In the perpendicular free layer, it is preferable that the magnetic anisotropy field caused by the material and the effective demagnetizing field in the direction perpendicular to the film surface of the perpendicular free layer substantially antagonize in the opposite direction. Furthermore, it is preferable that the vertical free layer is disposed closer to the main magnetic pole than the in-plane free layer.

  In the spin torque oscillation device of the present invention, the magnetization of the perpendicular free layer remains almost in the magnetization rotation plane, and therefore the angle with the magnetic anisotropy axis hardly changes before and after the polarity reversal of the main pole. Since the in-plane free layer magnetization remains almost in the plane of rotation, the recording medium can be written immediately after the main magnetic pole polarity is reversed. By applying the spin torque oscillation element of the present invention, the rotation state can be rapidly changed with respect to the applied magnetic field. As a result, it is possible to realize an information transfer rate exceeding 2 Gbit / s in magnetic recording using microwave assist recording in which the recording density exceeds 1 Tbit per square inch.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

The figure which shows the principle of MAMR. The figure which shows the magnetic field created from FGL. The figure which shows the relationship between the direction of the external magnetic field and STO drive current in the conventional STO. The figure which shows the relationship between the direction of the external magnetic field and STO drive current in the conventional STO. The figure which shows the calculation model of STO. The figure which shows the time change of the fixed layer magnetization z component and FGL magnetization z component in conventional STO. FIG. 4B is a diagram showing a time change of the FGL magnetization x component in the conventional STO. FIG. 4C is a diagram showing a time change of the fixed layer magnetization x component in the conventional STO. The figure which shows the rotation direction of the fixed layer magnetization and FGL magnetization in conventional STO. FIG. 5A is a diagram showing a time change of the external magnetic field reversal used in the calculation. FIG. 5B is a diagram showing a time change of the fixed layer magnetization z component in the conventional STO. FIG. 5C is a diagram showing a time change of the FGL magnetization z component in the conventional STO. FIG. 5D is a diagram showing a time change of the FGL magnetization x component in the conventional STO. The figure which shows the time change of perpendicular free layer magnetization z component at the time of the external magnetic field reversal of STO of this invention, and in-plane free layer magnetization z component. FIG. 6B is a diagram showing the time change of the in-plane free layer magnetization x component of the STO of the present invention. FIG. 6C is a diagram showing the time change of the perpendicular free layer magnetization x component of the STO of the present invention. The figure which shows the rotation direction of in-plane free layer magnetization and perpendicular | vertical free layer magnetization of STO of this invention. The figure which shows the external magnetic field dependence of AF mode oscillation frequency of STO. The figure which shows the result of having investigated the state of AF mode oscillation by changing a perpendicular magnetic anisotropy magnetic field with respect to the combination of magnetization and thickness of a perpendicular free layer. The figure which shows the external magnetic field dependence of the STO oscillation frequency which made electric current amount a parameter. The figure which shows the dependence of the in-plane magnetization component of an in-plane free layer with respect to the value which pulled the effective demagnetizing field from the magnetic anisotropic magnetic field resulting from a material in various conditions. FIG. 8A is a diagram showing a change over time of the external magnetic field reversal used in the calculation. FIG. 8B is a diagram showing a time change of the perpendicular free layer magnetization z component of the STO of the present invention. FIG. 8C is a diagram showing the time change of the in-plane free layer magnetization z component of the STO of the present invention. FIG. 8D is a diagram showing the time change of the in-plane free layer magnetization x component of the STO of the present invention. FIG. 9A is a diagram showing a time change of fast external magnetic field reversal used for calculation. FIG. 9B is a diagram showing a time change of the z component of the perpendicular free layer magnetization of the STO of the present invention. FIG. 9C is a diagram showing a time change of the in-plane free layer magnetization z component of the STO of the present invention. FIG. 10A is a time enlarged view of FIG. 9A. FIG. 10B is a time enlarged view of FIG. 9B. FIG. 10C is a time enlarged view of FIG. 9C. FIG. 10B is a diagram showing the rotation directions of the perpendicular free layer magnetization and the in-plane free layer magnetization at 2.5 nsec in FIGS. 10B and 10C. 10B is a diagram showing the rotation directions of the perpendicular free layer magnetization and the in-plane free layer magnetization at 3.5 ns in FIGS. 10B and 10C. FIG. The figure which shows how to obtain | require the high frequency magnetic field component effective for magnetization reversal. The schematic block diagram which shows the structure of STO. The figure which shows the distance dependence from the main magnetic pole of an effective high frequency magnetic field component. The schematic block diagram which shows the structure of STO. The figure which shows the distance dependence from the main magnetic pole of an effective high frequency magnetic field component. The schematic block diagram which shows the structure of STO. The figure which shows the distance dependence from the main magnetic pole of an effective high frequency magnetic field component. The schematic block diagram which shows the structure of STO. The figure which shows the distance dependence from the main magnetic pole of an effective high frequency magnetic field component. The figure which shows the relationship between the oscillation frequency of STO of this invention, and an external magnetic field. The figure which shows the relationship between the oscillation frequency of STO of this invention, and an external magnetic field. The figure which shows the relationship between the oscillation frequency of STO of this invention, and an external magnetic field. 1 is a schematic sectional view of a magnetic recording head according to an embodiment of the present invention. The figure which shows the relationship between the oscillation frequency of only STO, and an external magnetic field. The expanded sectional view of a slider and the recording / reproducing part mounted in it. The enlarged view of a magnetic head part. FIG. 3 is a diagram illustrating a configuration example of a magnetic head slider and a magnetic head. FIG. 3 is a diagram illustrating a configuration example of a magnetic head slider and a magnetic head. 1 is a schematic top view of a magnetic recording apparatus. FIG. 22A is a cross-sectional view taken along the line AA ′ of FIG.

  During the oscillation test of the MAMR STO prototype head, when a STO drive current in the opposite direction to that of the prior art was applied, a behavior that was considered to enable high-speed switching of the main pole polarity was observed. For the purpose of analyzing a new oscillation state that has not been considered in the past, the following LLG (Landau Lifschitz Gilbert) equation (1 The magnetization reversal behavior was analyzed by computer simulation based on). Here, the fixed layer or the perpendicular free layer is formed of a magnetic film having a magnetic anisotropy axis in a direction perpendicular to the film surface, and the FGL or the in-plane free layer is effectively a magnetic film having an easy magnetization surface on the film surface. Consists of. FIG. 3 is a diagram showing an STO calculation model.

ここで、γ，Ｉ，μ_B，ｅ，Ｐ は、それぞれ、ジャイロ磁気定数、膜面垂直方向の電流（Jは電流密度）、ボーア磁子、素電荷、分極率である。ｍ_h，Ｈ_h-eff，α_h，Ｖ_h，Ｍ_sh は、それぞれ、面内自由層２（又はＦＧＬ３２）の単位ベクトル、有効磁界、ダンピング定数、体積、飽和磁化である。また、ｍ_p，Ｈ_p-eff，α_p，Ｖ_p，Ｍ_sp は、それぞれ、垂直自由層１（又は固定層３１）の単位ベクトル、有効磁界、ダンピング定数、体積、飽和磁化である。面内自由層２の有効磁界Ｈ_h-effは、磁気異方性磁界Ｈ_ah（＝Ｈ_kh×cosθ_mh、θ_mhは面内自由層磁化とｚ軸のなす角）、静磁界Ｈ_sh、反磁界Ｈ_dh、及び外部磁界Ｈ_extの３成分の和で構成される。また、垂直自由層１の有効磁界Ｈ_p-effは、磁気異方性磁界Ｈ_ap（＝Ｈ_kp×cosθ_mp、θ_mpは垂直自由層磁化とｚ軸のなす角）、静磁界Ｈ_sp、反磁界Ｈ_dp、及び外部磁界Ｈ_extの３成分の和で構成される。静磁界Ｈ_sh，Ｈ_spは、図３の空間配置に示すように、面内自由層２と垂直自由層１とが平行で３ｎｍ離れている場合について、互いの磁化の影響を算出した。面内自由層２と垂直自由層１との間隙は、交換相互作用を伝えずに電流にてスピン情報を伝達すＣｕなどの非磁性スピン伝導層のためのものであり、層厚は３ｎｍに限定されるものではない。

Here, γ, I, μ _B , e, P are a gyro magnetic constant, a current in the direction perpendicular to the film surface (J is a current density), a Bohr magneton, an elementary charge, and a polarizability, respectively. m _h , H _h-eff , α _h , V _h , and M _sh are the unit vector, effective magnetic field, damping constant, volume, and saturation magnetization of the in-plane free layer 2 (or FGL 32), respectively. Further, m _p , H _p-eff , α _p , V _p , and M _sp are the unit vector, effective magnetic field, damping constant, volume, and saturation magnetization of the vertical free layer 1 (or the fixed layer 31), respectively. The effective magnetic field H _h-eff of the in _- plane free layer 2 is the magnetic anisotropy field H _ah (= H _kh × cos θ _mh , θ _mh is the angle formed by the in-plane free layer magnetization and the z axis), the static magnetic field H _sh , It is composed of the sum of three components of a demagnetizing field H _dh and an external magnetic field H _ext . The effective magnetic field H _p-eff of the vertical free layer 1 is a magnetic anisotropy magnetic field H _ap (= H _kp × cos θ _mp , θ _mp is an angle formed by the vertical free layer magnetization and the z axis), a static magnetic field H _sp , It is composed of the sum of three components of a demagnetizing field H _dp and an external magnetic field H _ext . As shown in the spatial arrangement of FIG. 3, the static magnetic fields H _sh and H _sp were calculated from the influence of mutual magnetization when the in-plane free layer 2 and the vertical free layer 1 were parallel and separated by 3 nm. The gap between the in-plane free layer 2 and the vertical free layer 1 is for a non-magnetic spin conduction layer such as Cu that transmits spin information by electric current without transmitting exchange interaction, and the layer thickness is 3 nm. It is not limited.

First, the calculation result of the oscillation state is shown for a conventional STO. The calculation model is as follows: a fixed layer 31 having a width of 40 nm, a height of 40 nm, a thickness of 10 nm, a saturation magnetic flux density of 1.5 T, and a perpendicular magnetic anisotropy H _kp of 960 kA / m (12 kOe); A soft magnetic material having a height of 40 nm × thickness of 12 nm and a saturation magnetic flux density of 2.3 T was assumed. 4A to 4D are diagrams showing temporal changes in fixed layer magnetization and FGL magnetization when a current is passed from the fixed layer 31 side to the FGL 32 side as in a conventional STO. The external magnetic field H _ext was applied with an intensity of 480 kA / m in the + z direction, and the magnitude of the STO drive current was 0.1 TA / m ² . In addition, since the current density value shown by this specification changes with various conditions, the effect of this invention is not limited to the described current density value. Figure 4A is the z-component of the fixed layer magnetization M _fixed and FGL magnetization M _FGL, Figure 4B FGL magnetization of the x component M _FGL-x, FIG. 4C saturate the x component M _{fixed -x} pinned layer magnetizations of each of the magnetic layer Values normalized by magnetization (M _sFGL , M _{s fixed} ) are shown. FIG. 4D shows the rotation directions of the fixed layer magnetization and the FGL magnetization.

  In FIG. 4A, since the z component of the magnetization does not change from 1.3 nsec to 10 nsec in both the fixed layer magnetization and the FGL magnetization, the constant angle with the + z axis direction (magnetic field application direction) is maintained. Recognize. In FIG. 4A, the reason why the magnetization has increased after decreasing once is that the initial condition used in this simulation is in a relatively high energy state, and it was necessary to release this energy first.

  4B, since the x component of the FGL magnetization orthogonal to the z axis is regularly oscillated by a sine wave, the FGL magnetization is tilted about 90 degrees from the z axis (xy plane), and the z direction is It is inferred that it is rotating as an axis. The number of rotations (vibrations) is about 23 GHz because 4.6 rotations per 0.2 nsec. Since MAMR uses a high-frequency magnetic field generated by switching the magnetization appearing on the FGL side surface at high speed, it is preferable that the FGL magnetization rotates in the xy plane as much as possible. The angle of the FGL magnetization from the + z-axis direction and the magnetization rotation speed increase as the current flowing from the STO fixed layer side to the FGL side increases. Therefore, in the conventional STO, there is a possibility that the current value at which the optimum rotation (vibration) number for the magnetization reversal of the recording medium is not matched with the current value at which the FGL magnetization rotates in the xy plane.

  Next, referring to FIG. 4C, the fixed layer magnetization is regularly oscillated by a sine wave as in the FGL magnetization. From this, it is inferred that the fixed layer magnetization oscillates while being tilted from the z-axis, though very little. Although it is considered that the fixed layer magnetization fluctuates due to the FGL magnetization, if the fixed layer magnetization is not sufficiently fixed and the fluctuation increases, stable in-plane rotation of the FGL magnetization cannot be obtained.

  Hereinafter, the conventional oscillation mode in which the magnetization of the fixed layer 31 is directed substantially in the + z-axis direction and the magnetization of the FGL 32 is rotated in the plane will be referred to as T-mode oscillation. In T mode oscillation, when a current is passed from the fixed layer 31 side to the FGL 32 side, electrons (spin) that attempt to make the FGL magnetization antiparallel to the fixed layer magnetization are reflected from the fixed layer, and the FGL magnetization is rotated by the spin torque action. To do. In order to obtain a stable oscillation (magnetization rotation) state, the fixed layer magnetization needs to be sufficiently fixed. In a conventional STO using T-mode oscillation, oscillation tends to be disturbed when the external magnetic field is weak, the perpendicular magnetic anisotropy of the fixed layer is weak, or the fixed layer is thin. This is considered because the fixed layer is not sufficiently fixed.

  FIG. 4D shows how the magnetization moves during a minute time of about 0.01 ns in order to investigate the rotation direction of each magnetization. Here, θ is an angle from the + z-axis direction of each magnetization, and φ is an angle from the + x-axis direction when each magnetization is projected onto the xy plane. It can be seen that both the FGL magnetization and the fixed layer magnetization move in the direction in which φ increases, and the rotation is clockwise around the + z-axis direction where the external magnetic field is applied. In the case of MAMR, when the STO is arranged in the vicinity of the main magnetic pole during MAMR and the magnetic field from the main magnetic pole is used as the magnetic field applied to the STO, the high frequency rotating magnetic field with high magnetization reversal efficiency of the recording medium is the main magnetic pole and the STO. Is the preferred direction of rotation generated between

5A to 5D show temporal changes of the fixed layer magnetization and the FGL magnetization when the external magnetic field is reversed in the T mode (conventional STO). FIG. 5A shows a time profile of an external magnetic field whose polarity reverses from the minus z direction to the plus z direction at t = 5 ns, and is a hyperbolic secant function that takes about 0.2 ns from the start of inversion to the completion of inversion. (Tanh) was used. FIG. 5B shows the magnetization reversal (z component) of the fixed layer, FIG. 5C shows the FGL magnetization reversal (z component), and FIG. 5D shows the FGL magnetization rotation (x component) about the z direction. The external magnetic field H _ext was 480 kA / m, the perpendicular magnetic anisotropy H _kp of the fixed layer was 960 kA / m, and the magnitude of the STO drive current was 0.1 TA / m ² .

5A and 5B, the fixed layer magnetization starts to rotate after the reversal of the external magnetic field is completed, and it takes 0.25 nsec until the reversal is completed. From FIG. 5B and FIG. 5C, the FGL magnetization is greatly deviated from the stable oscillation position (M _vz = 0) at which the output magnetic field becomes maximum at the initial stage of the reversal of the fixed layer magnetization. Since the STO drive (DC) current continues to flow during the reversal of the fixed layer magnetization, it is considered that the spin torque from the fixed layer acts to move the FGL magnetization away from the stable oscillation position. It takes about 0.2 nsec to return the FGL magnetization to the stable oscillation position. Therefore, about 0.7 nsec is required from the start of reversal of the external magnetic field to the stable oscillation state. According to FIG. 5D, during this period, the FGL is in an irregular oscillation state, and it is assumed that sufficient assist recording cannot be performed.

6A to 6D are diagrams showing temporal changes in the magnetization of the vertical free layer 1 and the magnetization of the in-plane free layer 2 constituting the STO of the present invention. As in FIG. 4, the calculation model is 40 nm wide × 40 nm high × 10 nm thick as the vertical free layer 1 (fixed layer in FIG. 4), the saturation magnetic flux density is 1.5 T, and the vertical magnetic anisotropy H _kp is Assuming a magnetic material of 960 kA / m (12 kOe), a soft magnetic material of width 40 nm × height 40 nm × thickness 12 nm and saturation magnetic flux density 2.3 T as the in-plane free layer 2 (FGL 32 in FIG. 4), Contrary to the case of FIG. 4, it was made to flow from the in-plane free layer 2 side to the vertical free layer 1 side. The external magnetic field H _ext was applied with an intensity of 480 kA / m in the + z direction, and the magnitude of the STO drive current was 0.1 TA / m ² . 6A shows the z component of the in-plane free layer magnetization M _h and the perpendicular free layer magnetization M _p , FIG. 6B shows the x component M _hx of the in-plane free layer magnetization, and FIG. 6C shows the x component M _px of the perpendicular free layer magnetization, respectively. The values normalized by the saturation magnetization (M _sh , M _sp ) of the magnetic layer are shown. FIG. 6D shows the direction of magnetization rotation.

  In FIG. 6A, since the z component of the magnetization does not change from 1.3 nsec to 10 nsec in both the perpendicular free layer magnetization and the in-plane free layer magnetization, a constant angle with the + z axis direction (magnetic field application direction) is maintained. You can see that From FIG. 6B, since the x component of the in-plane free layer magnetization orthogonal to the z-axis is regularly oscillated by a sine wave, the in-plane free layer magnetization is tilted about 90 degrees from the z-axis (xy plane). ) Is presumed to rotate around the z direction. 6C, the perpendicular free layer magnetization is also regularly oscillated by a sine wave, and the perpendicular free layer magnetization is tilted about 80 degrees from the z axis (xy plane). It is inferred that it is rotating as an axis. Further, comparing FIG. 6B and FIG. 6C, the phases are shifted from each other by about 180 degrees, so that the perpendicular free layer magnetization and the in-plane free layer magnetization are almost opposite to each other and are rotated near the in-plane. I understand. The number of rotations (vibrations) is about 16 GHz because 3.1 rotations per 0.2 nsec. In FIG. 6A, the z component of both free layer magnetizations once increases and then converges in the vicinity of the in-plane (Mz = 0) because the initial condition used in this simulation is a relatively high energy state. This is because it was necessary to release this energy first. Once in the stable oscillation state, even if the polarity of the external magnetic field is changed, a high energy state is not immediately obtained.

  FIG. 6D shows how the magnetization moves during a minute time of about 0.01 ns in order to investigate the rotation direction of each magnetization. The definitions of the angles θ and φ are the same as in FIG. 4D. It can be seen that both the in-plane free layer magnetization and the perpendicular free layer magnetization move in the direction in which φ increases and rotate clockwise in the + z-axis direction where an external magnetic field is applied. In the case of MAMR, when the STO is arranged in the vicinity of the main magnetic pole during MAMR and the magnetic field from the main magnetic pole is used as the magnetic field applied to the STO, the high frequency rotating magnetic field with high magnetization reversal efficiency of the recording medium is the main magnetic pole and the STO. Is the preferred direction of rotation generated between

  This newly discovered oscillation mode of the present invention in which the perpendicular free layer magnetization and the in-plane free layer magnetization are antiparallel and substantially rotated in the xy plane is hereinafter referred to as AF mode oscillation. . In AF mode oscillation, the in-plane free layer magnetization follows the perpendicular free layer magnetization by the spin torque generated by passing a current from the in-plane free layer side to the vertical free layer side, and the vertical free layer magnetization is changed to the in-plane free layer magnetization. The action to escape is balanced autonomously. Further, the in-plane free layer magnetization rotates approximately in the xy plane, whereas the perpendicular free layer magnetization slightly tilts in the direction of the external magnetic field from the xy plane. For this reason, even if the direction of the external magnetic field is reversed, the deviation of the inclination of the perpendicular free layer magnetization from the z-axis is small, and it is expected that the switching can be performed promptly.

In FIG. 7A, a soft magnetic material having a width of 40 nm × height of 40 nm × thickness of 12 nm and a saturation magnetic flux density of 2.3 T is used as the in-plane free layer, and the width of 40 nm × height of 40 nm × thickness (t _p is used as the vertical free layer. ) 3 nm in saturation magnetic flux density B _sp is 1.5T, the vertical magnetic anisotropy due to the material H _kp is 0.48MA / m (6kOe), 0.80MA / m (10kOe), 1.12MA / m (14kOe ), The dependence of the AF mode oscillation frequency on the external magnetic field when a 1.44 MA / m (18 kOe) magnetic material is used. Effective demagnetizing field H _dp-eff (= 4πM _sp × (N _pz −N _px )) in the direction perpendicular to the film surface of the vertical free layer, M _sp is the saturation magnetization of the vertical free layer, N _pz and N _px are the z direction and x The directional magnetic field coefficient is 1.09 MA / m. The STO drive current is passed from the in-plane free layer side to the vertical free layer side.

Referring to FIG. 7A, the oscillation frequency increases as the external magnetic field _Hext is applied more strongly under the conditions of each perpendicular magnetic anisotropy. However, when the value of H _ext + H _kp reaches a fixed value (here, about 2000 kA / m) determined by the current value and the value of the effective magnetic field in the vertical direction of the vertical free layer, the magnetization of the vertical free layer is in-plane. AF mode oscillation cannot be maintained because the magnetic field application direction cannot be maintained. As perpendicular magnetic anisotropy field H _kp of vertical free layer is small, seems to have been obtained higher oscillation frequency, as long as H _kp has the higher high oscillating STO is the external magnetic field H _ext is certain conditions An oscillation frequency is obtained. In MAMR, in order to record on a medium corresponding to a higher recording density, it is necessary to increase the oscillation frequency of STO. It is effective to use a vertical free layer having a high H _kp as much as possible so as to increase the external (gap) magnetic field applied to the STO and oscillate accordingly.

In order to realize MAMR by obtaining a stable oscillation (magnetization rotation) state in the AF mode, the setting of perpendicular magnetic anisotropy is a key point. 7B is a saturation magnetic flux density B _sp vertical free layer, for various combinations of thickness t _p, the state of the AF mode oscillation by changing the perpendicular magnetic anisotropy field H _kp due to the material of the vertical free layer It is the result of investigation. For each combination, when the value obtained by subtracting the effective demagnetizing field H _dp-eff in the vertical direction from H _kp is smaller than −250 kA / m, the oscillation may not be stable. In FIG. 7A, when the perpendicular magnetic anisotropy is 480 kA / m and 800 kA / m, the oscillation is unstable in the low magnetic field region where H _ext is 250 kA / m. H _dp-eff is subtracted from H _kp. It is considered that the measured values are too small, −610 (= 480-1090) kA / m and −290 (= 800-1090) kA / m, respectively. When the value obtained by subtracting H _dp-eff from H _kp is larger than 400 kA / m, AF mode oscillation cannot be excited. It is considered that the magnetization of the perpendicular free layer is oriented in the direction of the perpendicular magnetic anisotropy axis and does not become the AF mode. The effective demagnetizing field in the direction perpendicular to the magnetic field and the film surface must be reversed and almost antagonized. The value obtained by subtracting H _dp-eff from H _kp needs to be between −250 kA / m and 400 kA / m. Within the above range, a higher oscillation frequency can be obtained when H _kp > H _dp-eff . However, a break-in oscillation of about 1 to 2 n seconds is required after the STO drive current is input and before the perpendicular free layer magnetization falls from the perpendicular direction to the in-plane direction before entering the writing state. When H _kp <H _dp-eff , the write state can be entered immediately after the STO drive current is input.

FIG. 7C shows an STO having a width of 40 nm, a height of 40 nm, a thickness of 3 nm, a saturation magnetic flux density of 1.5 T, and a perpendicular magnetic anisotropy H _kp of 1.12 MA / m as a vertical free layer. This shows the dependence of the oscillation frequency on the external magnetic field when the current amount is 0.4 TA / m ² and the current amounts are 0.1 and 1.6.

Under each current condition, the oscillation frequency increases as the external magnetic field H _ext is applied more strongly. As long as the STO oscillates under a condition where the external magnetic field H _ext is constant, the smaller the current value, the higher the oscillation frequency can be obtained, but the higher the current value, the higher the oscillation frequency can be obtained. The highest current can be obtained by increasing the current that can be applied to the STO, increasing the external (gap) magnetic field applied to the STO, and using a vertical free layer having the largest possible perpendicular magnetic anisotropy H _kp that oscillates accordingly. An oscillation frequency is obtained. In the STO of the present invention using the AF mode oscillation, since the in-plane free layer magnetization is substantially in-plane, appropriate perpendicular free layer magnetization and perpendicular magnetic anisotropy with respect to a combination of an external (gap) magnetic field and a current value. By setting the characteristics, it is possible to maximize the high-frequency output (magnetic field) at the optimum rotation (vibration) number for the magnetization reversal of the recording medium. The STO of the present invention is assumed to be installed between the main magnetic pole and the auxiliary magnetic pole, and it is effective to reduce the distance between the main magnetic pole and the auxiliary magnetic pole in order to increase the external (gap) magnetic field.

FIG. 7D shows that the in-plane magnetization component M _h-xy of the in _- plane free layer in the AF mode oscillation state under various conditions is obtained by subtracting the effective demagnetizing field H _dh-eff from the perpendicular magnetic anisotropic magnetic field H _kh caused by the material. It is shown as a function of the value. In the figure, H _hk is changed, and assuming that a negative magnetic anisotropic material such as a (Co / Fe) n multilayer film is used, a negative H _hk can be obtained. The fact that H _{hk of the} perpendicular magnetic anisotropy is a negative value means that the magnetic anisotropy is of the easy magnetization surface type. In the figure, M _h-xy is normalized by the saturation magnetization M _{sh of the} in _- plane free layer. If the value of M _h-xy / M _sh is 1.0, the in-plane free layer magnetization is in-plane. This means that there is a maximum high-frequency magnetic field strength.

FIG. 7D shows that the maximum high-frequency magnetic field strength can be obtained if the value of H _kh -H _dh-eff is smaller than −200 kA / m even under various conditions. Therefore, application to the in-plane free layer of the negative perpendicular magnetic anisotropic material CoIr alloy, CoFeIr alloy, and (Co / Fe) n multilayer film having an easy magnetization surface has a narrow track width and an effective demagnetizing field. This is particularly effective in a head with high track density that can be reduced. From the above, the in-plane free layer is a magnetic film in which the effective demagnetizing field is dominant compared to the magnetic anisotropy field caused by the material perpendicular to the film surface, that is, the film surface has an easy-magnetization surface effectively. It turns out that there is a need.

FIGS. 8A to 8D show temporal changes of the perpendicular free layer magnetization and the in-plane free layer magnetization when the external magnetic field is reversed in the AF mode (STO of the present invention). Of the conditions at the top of FIG. 7B, the perpendicular magnetic anisotropy H _kp of 960 kA / m (H _kp −H _dp-eff = −130 kA / m) was used. The magnitude of the external magnetic field H _ext is 480 kA / m, and the STO drive current is 0.3 TA / m ² . FIG. 8A shows a time profile of an external magnetic field whose polarity is reversed from the minus z direction to the plus z direction at t = 5 ns. (Tanh) was used. 8B shows the magnetization reversal (z component) of the vertical free layer, FIG. 8C shows the reversal of the in-plane free layer magnetization (z component), and FIG. 8D shows the rotation of the in-plane free layer magnetization about the z direction (x component). Indicated.

8A and 8B, the perpendicular free layer magnetization starts rotating simultaneously with the start of reversal of the external magnetic field, and completes simultaneously with the completion of reversal of the external magnetic field. 8B and 8C, the in-plane free layer magnetization hardly deviates from the stable oscillation position (M _vz = 0) at which the output magnetic field is maximum while the vertical free layer magnetization is reversed. Therefore, the time required from the start of reversal of the external magnetic field to the stable oscillation state is only about 0.2 nsec required for reversal of the external magnetic field. In this way, it was found that the state was switched while the perpendicular free layer magnetization and the in-plane free layer magnetization were kept substantially antiparallel, and high-speed switching was possible. It can be considered that the behavior of M _vx during this period seen in FIG. 8D reflects the situation where the in-plane rotation speed of the in-plane free layer magnetization is slow and the rotation direction is switched. This is consistent with the behavior of the oscillation frequency with respect to the external magnetic field in FIGS. 7A and 7C. Since the magnetic resonance frequency of the magnetic particles in the middle of reversal decreases when the magnetization of the magnetic recording medium is reversed, by using the STO of the present invention, the reversal of the magnetic particles in the middle of the magnetization reversal can be efficiently performed by reversing the external (write) magnetic field. Wave assist can be performed.

  In order to investigate the high-frequency response characteristic potential in the AF mode in detail, the time change of the high-speed reversal in which the reversal time of the external magnetic field shown in FIG. The application direction of the external magnetic field is the z direction. FIG. 9B shows the time change of the perpendicular free layer magnetization z component with respect to this, and FIG. 9C shows the time change of the in-plane free layer magnetization z component.

From FIG. 9B, it can be seen that the magnetization of the perpendicular free layer magnetization is completely reversed following the external magnetic field after 1 ns. In addition, as shown in FIG. 9C, the in-plane free layer magnetization is hardly deviated from the stable oscillation position (M _vz = 0) at which the output magnetic field becomes maximum after 1 _ns . Note that the behavior of the perpendicular free layer magnetization and the in-plane free layer magnetization before 1 ns is because the state greatly deviated from the good AF oscillation state is the initial state of the calculation, and it is sufficient if the AF mode oscillation state is once entered. It is considered that high-speed inversion characteristics can be obtained. When assist recording is performed in the AF mode oscillation state after a long pause, it is considered that break-in driving of about 1-2 n seconds is necessary.

  FIGS. 10A to 10C further expand the state of the magnetization behavior when switching the external magnetic field in the vicinity of 3 ns of FIGS. 9A to 9C. 10A corresponds to FIG. 9A, FIG. 10B corresponds to FIG. 9B, and FIG. 10C corresponds to FIG. 9C. As shown in FIG. 10B, the perpendicular free layer magnetization starts reversal immediately after reversal of the external magnetic field, and reversal is completed in about 0.1 nsec. During this time, as shown in FIG. 10C, the in-plane free layer magnetization is slightly displaced from the stable oscillation position.

  FIG. 10D shows the rotation directions of the perpendicular free layer magnetization and the in-plane free layer magnetization at 2.5 ns in FIGS. 10B and 10C. FIG. 10E shows the rotation directions of the perpendicular free layer magnetization and the in-plane free layer magnetization at 3.5 ns in FIGS. 10B and 10C. The definitions of the angles θ and φ are the same as in FIG. 4D. The rotation direction is reversed between the time of 2.5 ns and the time of 3.5 ns, and the rotation direction of the perpendicular free layer magnetization and the in-plane free layer magnetization is reliably switched according to the external magnetic field. Can be confirmed.

In order to examine the effect of microwave assisted magnetization reversal by the high frequency magnetic field generated from the STO in the AF mode oscillation state, the effective high frequency magnetic field component H _hf-eff is obtained. The high-frequency magnetic field adds the magnetic fields from the bottom surface (including the top bottom surface) and the side surface of the vertical free layer and the in-plane free layer. Generally, the magnetic field from the bottom and the magnetic field from the side are not orthogonal except on the track center. Considering this point, it is necessary to obtain a high-frequency magnetic field component H _hf-eff effective for microwave-assisted inversion generated from the FGL. As shown in FIG. 11, the high-frequency magnetic field H _hf is considered to be a combined magnetic field of the magnetic field H _b from the bottom surface and the magnetic field H _s from the side surface whose phases are shifted from each other by 90 degrees. It is expressed in

Here, the magnetic field component effective for assist is approximated to be parallel in the medium plane, and Equation (3) is obtained.

Substituting equation (3) into equation (2) yields the following equation (4).

  Further, when only the counterclockwise component acting on the microwave assisted magnetization reversal is considered and the exp (−iωt) term is ignored, the following equation (5) is obtained. The subscripts h and p of H mean an in-plane free layer and a vertical free layer, respectively.

FIGS. 12A and 12B to FIGS. 15A and 15B show the influence of the effective high-frequency magnetic field component H _{hf-eff in the} AF mode on the writing characteristics. In any case, the STO drive current is passed from the in-plane free layer 2 side to the vertical free layer 1 side. In the present study, the in-plane free layer 2 or the vertical free layer 1 is disposed 20 nm away from the main pole 5 as an example, but the effect of the present invention can be obtained without being limited by this value. Similarly, the gap for the nonmagnetic spin conductor between the in-plane free layer 2 and the vertical free layer 1 is 3 nm, but the effect of the present invention can be expected without using this value. The graph in the figure assumes that when a write magnetic field is applied to the recording medium, first, a magnetic field from the main pole 5 and then a high-frequency magnetic field from the STO are applied to the medium, and the H _hf-eff on the STO side is The change is shown with respect to the distance from the main pole end on the STO side. The writing point was the half-value point of the highest peak of H _hf-eff that was farther from the main pole. When the main magnetic pole polarity is reversed, a magnetization transition region is formed at the write point.

FIG. 12A is a schematic configuration diagram showing an example of the STO in which the vertical free layer 1 having the same thickness as the in-plane free layer 2 is disposed on the side opposite to the main magnetic pole 5. The thicknesses of the vertical free layer 1 and the in-plane free layer 2 were both 15 nm. The saturation magnetic flux density B _s of the in-plane free layer was 2.3T. The distance between the main pole 5 and the in-plane free layer 2 is 20 nm. FIG. 12B shows the distance dependency of H _{hf-eff from} the main magnetic pole tip when the saturation magnetic flux density of the vertical free layer 1 is 1.2 T and 2.4 T in the arrangement shown in FIG. 12A. For comparison, H _hf-eff by an in _- plane free layer alone (conventional STO FGL) is shown by a broken line with B _sp = 0.

The peaks of H _hf-eff are named as the first peak and the second peak from the main magnetic pole side. With increasing the saturation magnetic flux density B _sp vertical free layer, the second peak is the write point becomes larger than the first peak there is a main pole away from (25nm⇒50nm) problem, the effective high frequency magnetic field peak value, B _In the case of _sp = 2.4T, it becomes 1.3 times that of the conventional STO. Therefore, the STO of this embodiment is preferably combined with a head (main magnetic pole) that can influence the magnetic field even at a position away from the main magnetic pole.

FIG. 13A is a schematic configuration diagram showing an example of the STO in which the vertical free layer 1 thinner than the in-plane free layer is disposed on the side opposite to the main magnetic pole 5. The thickness of the vertical free layer 1 was 5 nm. The thickness of the in-plane free layer 2 was 15 nm, and the saturation magnetic flux density B _s was 2.3 T. The distance between the main pole 5 and the in-plane free layer 2 is 20 nm. FIG. 13B shows the distance dependence of H _{hf-eff from} the main pole tip when the saturation magnetic flux density of the vertical free layer 1 is 1.2 T and 2.4 T in the arrangement shown in FIG. 13A. As the B _{s of the} vertical free layer increases, the second peak becomes larger and approaches the main pole side, so there is a concern about the deterioration of the separation characteristics (re-inversion of magnetization due to the second peak). There is an advantage of being close to the main pole. Therefore, the STO of this embodiment is preferably combined with a head (main magnetic pole) having a high magnetic field gradient.

FIG. 14A is a schematic configuration diagram showing an example of the STO in which the vertical free layer 1 having the same thickness as the in-plane free layer is disposed between the main magnetic pole 5 and the in-plane free layer 2. The thicknesses of the vertical free layer 1 and the in-plane free layer 2 were both 15 nm. The saturation magnetic flux density B _s of the in-plane free layer 2 was 2.3T. The distance between the main pole 5 and the vertical free layer 1 is 20 nm. FIG. 14B shows the distance dependence of H _{hf-eff from} the main pole tip when the saturation magnetic flux density of the vertical free layer 1 is 1.2 T and 2.4 T in the arrangement shown in FIG. 14A. Although the writing point moves away from the main pole, the writing magnetic field peak is pushed up (in the case of B _sp = 2.4T, 1.3 times that of the conventional STO), and the third peak is effectively reduced. Therefore, the STO of this embodiment is preferably combined with a head (main magnetic pole) that can influence the magnetic field even at a position away from the main magnetic pole.

FIG. 15A is a schematic configuration diagram showing an example of the STO in which the vertical free layer 1 thinner than the in-plane free layer 2 is disposed between the main magnetic pole 5 and the in-plane free layer 2. The thickness of the in-plane free layer 2 was 15 nm, and the saturation magnetic flux density B _s was 2.3 T. The thickness of the vertical free layer 1 was 5 nm. The distance between the main pole 5 and the vertical free layer 1 is 20 nm. FIG. 15B shows the distance dependence of H _{hf-eff from} the main pole tip when the saturation magnetic flux density of the vertical free layer 1 is 1.2T and 2.4T in the arrangement shown in FIG. 15A. When the perpendicular free layer on the main pole side is thin, the effect of pushing up the write magnetic field peak is not significant, but the write point deviation hardly depends on the magnetization of the perpendicular free layer. Therefore, the STO of this embodiment can perform high-speed data transmission with the same write characteristics as the conventional STO.

16A to 16C are diagrams showing the dependence of the AF mode oscillation frequency on the external magnetic field when a current is passed from the in-plane free layer side to the vertical free layer side. The in-plane free layer uses a soft magnetic material having a width of 40 nm, a height of 40 nm and a thickness of 12 nm and a saturation magnetic flux density of 2.3 T, and the vertical free layer has a saturation magnetic flux density _Bsp of 1.5 T and perpendicular magnetic anisotropy. A magnetic material having a property H _kp of 0.96 MA / m (12 kOe), a width of 40 nm × a height of 40 nm, and a thickness changed to 6 nm, 3 nm, and 1.5 nm was used. It was found that when the current value was changed so that the oscillation characteristics did not change greatly depending on the thickness of the vertical free layer, the current value decreased almost in inverse proportion to the film thickness. From this, it is considered that the current value required for AF mode oscillation is determined mainly by the film thickness of the vertical free layer, unlike the conventional STO that oscillates in T mode. Therefore, in the STO that oscillates in the AF mode, it is possible to apply a thick in-plane free layer that can obtain a strong high-frequency magnetic field without greatly increasing the required drive current value.

  By combining with the STO structure shown in FIG. 13A and FIG. 15A, power saving and improvement of the oscillation frequency can be expected. When a magnetic material having negative magnetic anisotropy is used as the in-plane free layer, more stable oscillation characteristics can be obtained. Further, when the vertical free layer is arranged between the main magnetic pole and the in-plane free layer, there is an advantage that the degree of freedom in design is increased because the writing point does not change greatly depending on the magnetization and thickness of the vertical free layer.

  As described above, a magnetic recording device that records information by arranging a spin torque oscillation element in the vicinity of the main magnetic pole that generates a magnetization reversal magnetic field and generating a high-frequency magnetic field from the spin torque oscillation element to cause a magnetic resonance state and magnetization reversal of the recording medium. In the head, the spin torque oscillation element includes a vertical free layer made of a magnetic film having a magnetic anisotropy axis in a direction perpendicular to the film surface and an in-plane free layer made of a magnetic film having an easy-to-magnetize surface on the film surface. It was found that high-speed magnetization reversal characteristics can be obtained by flowing a substantially constant current from the in-plane free layer side to the vertical free layer side. Further, it has been found that by making the vertical free layer thinner than the in-plane free layer, power saving and an improvement in the oscillation frequency can be expected, and a high recording density can be achieved. It was also found that the degree of freedom in design is increased by installing the vertical free layer closer to the main pole than the in-plane free layer. Since the STO of the present invention does not require the perpendicular free layer to be strongly fixed during oscillation unlike the conventional STO, a material having a relatively small perpendicular magnetic anisotropy can be used. In this case, by using a magnetic material having a small damping constant, it is possible to reduce the current required for oscillation, and to suppress changes in material magnetism and deterioration of element characteristics due to electron migration or the like. On the other hand, since the in-plane free layer magnetization rotates substantially in the plane, a strong and stable high-frequency magnetic field can be obtained. From these facts, it was found that an information recording apparatus to which microwave assisted recording having a recording density exceeding 1 Tbit per square inch can be used to realize an information transfer speed exceeding 2 Gbit / s.

  It should be noted that the magnetizations of the equivalent two free layers separated by the nonmagnetic layer shown in Japanese Patent Application Laid-Open Nos. 2008-277586 and 2008-305486 are rotated in a substantially antiparallel coupled state. The technology in which magnetic fields between positive and negative magnets with equal amounts appearing on the ABS end face oscillate linearly in the medium plane is 1) a spin-polarized layer (fixed layer) is required 2) energization from the fixed layer side to the FGL side (The current direction is opposite to that of the STO of the present invention) 3) The thickness of the pair of free rotating layers is substantially equal. 4) The present invention is different from the present invention in that perpendicular magnetic anisotropy is not imparted to the free rotating layer. Is not relevant to the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail.
FIG. 17 shows a magnetic recording head according to an embodiment of the present invention cut along a plane perpendicular to the recording medium surface (vertical direction in the figure) and parallel to the head running direction (track direction which is the left or right direction in the figure). FIG. The figure also shows a cross section of the medium.

  The recording head 200 constitutes a magnetic circuit between the main magnetic pole 5 and the counter magnetic pole 6 in the upper part of the drawing. However, in the upper part of the drawing, it is assumed that it is electrically insulated. In the magnetic circuit, the magnetic lines of force form a closed circuit, and it is not necessary to be formed of only a magnetic material. Further, an auxiliary magnetic pole or the like may be arranged on the opposite side of the main magnetic pole 5 from the counter magnetic pole 6 to form a magnetic circuit. In this case, the main magnetic pole 5 and the auxiliary magnetic pole need not be electrically insulated. Further, it is assumed that the magnetic recording head 200 is provided with a coil, a copper wire and the like for exciting these magnetic circuits. The STO 201 of the present invention is formed between the main magnetic pole 5 and the counter magnetic pole 6. The main magnetic pole 5 and the counter magnetic pole 6 are provided with an electrode or a means for making electrical contact with the electrode, and an STO drive current from the main magnetic pole 5 side to the counter magnetic pole 6 side or vice versa can flow through the in-plane free layer 2. It is configured as follows. The material of the main magnetic pole 5 and the counter magnetic pole 6 was a CoFe alloy having a large saturation magnetization and almost no magnetocrystalline anisotropy. The recording medium 7 is a laminated film in which a 10 nm-Ru layer is formed on a substrate 19 as a base layer 20 on a 30 nm-CoFe, and a magnetic anisotropic magnetic field is 1.6 MA / m (20 kOe) as a recording layer 16. A CoCrPt—SiOx layer having a thickness of 10 nm was used.

  An STO 201 comprising a nonmagnetic spin scattering layer 8, a perpendicular free layer 1, a nonmagnetic spin conduction layer 3, an in-plane free layer 2, and a second nonmagnetic spin scattering layer 9 is formed in layers adjacent to the main pole 5. To the opposing magnetic pole 6. Note that the nonmagnetic spin scattering layer 8 to the second nonmagnetic spin scattering layer 9 have a columnar structure extending in the left-right direction of the drawing, and have a rectangular cross section with a long direction along the ABS surface. By adopting the rectangular shape, shape anisotropy occurs in the track width direction, and therefore, in-plane magnetization rotation of the in-plane free layer 2 even if there is an in-plane component of the in-plane free layer 2 of the leakage magnetic field from the main pole. Thus, the main magnetic pole 5 and the in-plane free layer 2 can be brought close to each other. However, when the leakage magnetic field from the main pole is small, there is no problem even if the cross-sectional shape is square. The side length w along the ABS surface of these cross-sectional shapes is an important factor for determining the recording track width, and is 40 nm in this embodiment. In the microwave assisted recording, a recording medium having a large magnetic anisotropy that cannot be recorded unless the recording magnetic field from the main magnetic pole 5 and the high-frequency magnetic field from the vertical free layer 1 and the in-plane free layer 2 are aligned is used. Therefore, the width and thickness of the main pole 5 (length in the head running direction) can be set large so that a large recording magnetic field can be obtained. In this embodiment, a recording magnetic field of about 0.9 MA / m is obtained by setting the width to 80 m and the thickness to 100 nm.

  For the vertical free layer 1, a 5 nm- (Co / Ni) n multilayer film was used. The magnetic field applied to the STO of this example is 40 nm from the end face of the main magnetic pole 5 to the end face of the counter magnetic pole 6 and the height of the in-plane free layer 2 is 38 nm. Therefore, the magnetic field is analyzed using 3D magnetic field analysis software. As a result, it is about 0.8 MA / m (10 kOe). The in-plane free layer 2 was a CoFe alloy having a thickness of 15 nm with a large saturation magnetization and almost no magnetocrystalline anisotropy. In the in-plane free layer 2, the magnetization rotates at a high speed in the plane along the layer, and the leakage magnetic field from the magnetic poles appearing on the ABS surface and the side surface acts as a high-frequency magnetic field. A material with a large saturation magnetization having negative perpendicular magnetic anisotropy, such as a (Co / Fe) n multilayer film, may be used for the in-plane free layer 2. In this case, the in-plane rotation of the in-plane free layer magnetization is stabilized.

  In the STO 201 of this embodiment, since the vertical free layer 1 is between the main magnetic pole 5 and the in-plane free layer 2, STO drive from the counter magnetic pole 6 side to the main magnetic pole 5 side to obtain the AF mode spin torque oscillation ( (DC) current needs to flow. When the magnetic flux flows from the main magnetic pole 5 side, the rotation direction of the magnetization of the in-plane free layer 2 is counterclockwise when viewed from the upstream side of the STO drive (DC) current, and the magnetic field from the main magnetic pole 5 A rotating magnetic field having the same direction as the direction of precession of magnetization of the recording medium to be reversed can be applied. When a magnetic field flows into the main magnetic pole 5, the rotation direction of the magnetization of the in-plane free layer 2 is clockwise when viewed from the upstream side of the high-frequency drive (DC) current, and is reversed by the magnetic field applied to the main magnetic pole 5. A rotating magnetic field having the same direction as the direction of precession of magnetization can be applied. Therefore, the rotating high frequency magnetic field generated from the in-plane free layer 2 has an effect of assisting the magnetization reversal by the main magnetic pole 5 regardless of the polarity of the main magnetic pole 5. This effect cannot be obtained with the high-frequency magnetic field generator of Patent Document 1 in which the direction of the spin torque does not change depending on the polarity of the main magnetic pole 5.

  The spin torque action increases as the STO drive current increases, and increases when a Co or CoFeB layer having a high polarizability is inserted between the nonmagnetic spin conduction layer 3 and the adjacent layer by about 1 nm. For the nonmagnetic spin conduction layer 3, 2 nm-Cu was used. For the nonmagnetic spin scattering layers 8 and 9, 3 nm-Ru was used. Even if Pd or Pt is used, the same effect is obtained. The nonmagnetic spin scattering layers 8 and 9 have an effect of preventing the interaction between the STO and the main magnetic pole 5 and the counter magnetic pole 6 via the spin torque by scattering the spin information. Without the nonmagnetic spin scattering layers 8 and 9, the STO oscillation may not be stable. In the simulations so far and in the examples of FIGS. 12 to 15, the nonmagnetic spin conduction layer 3 and the nonmagnetic spin scattering layers 8 and 9 are not considered. However, since they are nonmagnetic, they interact magnetically with STO. Furthermore, since it is a nanometer-order structure, it is considered that there is almost no influence on the generated high-frequency magnetic field.

FIG. 18 shows the result of measuring the relationship between the oscillation frequency of the STO only and the external magnetic field by removing the main magnetic pole 5, the nonmagnetic spin scattering layers 8 and 9, and the counter magnetic pole 6 from the prototype head shown in FIG. FIG. For the vertical free layer, 40 nm × 40 nm × 5 nm, H _kp = 1280 kA / m (16 kOe), B _s = 1.2 T, (Co / Pt) n multilayer film was used (H _kp −H _dp-eff = 280 kA / m) ). It can be seen that in the AF mode, the oscillation frequency increases in proportion to the applied external magnetic field. When the thickness of the perpendicular free layer is 10 nm (H _kp −H _dp-eff = 470 kA / m), 15 nm (H _kp −H _dp-eff = 650 kA / m), or a large perpendicular magnetic anisotropy H _kp When = 1440 kA / m (18 kOe, H _kp -H _dp-eff = 440 kA / m), no oscillation occurred. This is probably because a sufficient demagnetizing field was not obtained. Further, when the (Co / Pd) n multilayer film and the (Co / Pt) n multilayer film were used for the vertical free layer, oscillation did not occur even when the thickness tp was changed in the range of 5 nm to 15 nm. This is probably because the perpendicular magnetic anisotropy was too large compared to the saturation magnetization, and a sufficient demagnetizing field could not be obtained even if it was made thin. As in this embodiment, when using an STO that oscillates in an AF mode by applying a magnetic field from the outside without bringing a magnetic material close to the spin torque oscillator (STO) of the present invention, the main magnetic pole 5 and the nonmagnetic spin The scattering layers 8 and 9 and the counter magnetic pole 6 are not necessary.

  As shown in the schematic diagram of FIG. 19, the magnetic head slider 102 mounted with the recording / reproducing unit 109 incorporating the STO 201 of the present invention was attached to the suspension 106, and the recording / reproducing characteristics were examined using a spin stand.

  The recording / reproducing unit 109 includes a recording head unit and a reproducing head unit. As shown in the enlarged view in the figure, the recording head portion is composed of an auxiliary magnetic pole 206, an STO 201 disposed between the main magnetic pole 5 and the counter magnetic pole 6, a coil 205 for exciting the main magnetic pole, and the like. The reproducing head unit includes a reproducing sensor 207 disposed between the lower shield 208 and the upper shield 210. The auxiliary magnetic pole 206 and the upper shield 210 may be used in combination. The drive current of each component of the recording / reproducing unit 109 is fed by the wiring 108 and supplied to each component by the terminal 110. In the enlarged view, the power source 202 for flowing current to the STO 201 is schematically shown. However, the power source 202 is actually installed outside the slider 102, and the STO driving current from the power source 202 is supplied to the STO 201 via the wiring 108. Supplied.

  Magnetic recording was performed at a head medium relative speed of 20 m / s, a magnetic spacing of 7 nm, and a track pitch of 50 nm, and this was reproduced by a GMR head having a shield interval of 15 nm. When the STO drive voltage was changed and a 1300 kFCI signal was recorded at 512 MHz, a maximum signal / noise ratio of 13.1 dB was obtained when the STO drive voltage was 150 mV. Further, when a 2600 kFCI signal was recorded at 1024 MHz, the maximum signal / noise ratio was 8.0 dB. From this, it was found that an information transfer rate exceeding 2 Gbit / s can be realized at a recording density exceeding 1 Tbit per square inch. The frequency of the high frequency magnetic field at this time was 30 GHz. When the conventional structure STO of T-mode oscillation that can obtain the same FGL (in-plane free layer) thickness and oscillation frequency is used, a substantially equivalent result is obtained when the head medium relative speed is 10 m / s. However, at 20 m / s, the signal / noise ratio when a 2600 kFCI signal was recorded was greatly degraded to a maximum of 3.0 dB. The conventional structure STO optimized for T-mode oscillation, even if the STO drive current is reversed, because the fixed layer (vertical free layer) is thick, the demagnetizing field is insufficient and cannot antagonize the perpendicular magnetic anisotropic magnetic field. AF mode oscillation does not occur.

  FIG. 20 shows a magnetic recording head having a main magnetic pole 5 receding from the STO according to an embodiment of the present invention perpendicular to the recording medium surface (up and down direction in the figure) and head running direction (left or right direction in the figure). It is the cross-sectional schematic diagram cut | disconnected by the surface parallel to a track direction). The figure also shows a cross section of the medium. By retracting the main magnetic pole 5 from the STO, a magnetic field component entering the STO laminated surface from the main magnetic pole 5 can be reduced, and a reliable operation of the STO is expected.

  The recording head 200 constitutes a magnetic circuit between the main magnetic pole 5 and the counter magnetic pole 6 in the upper part of the drawing. However, in the upper part of the drawing, it is assumed that it is electrically insulated. In the magnetic circuit, the magnetic lines of force form a closed circuit, and it is not necessary to be formed of only a magnetic material. Further, an auxiliary magnetic pole or the like may be arranged on the opposite side of the main magnetic pole 5 from the counter magnetic pole 6 to form a magnetic circuit. In this case, the main magnetic pole 5 and the auxiliary magnetic pole need not be electrically insulated. Further, it is assumed that the magnetic recording head 200 is provided with a coil, a copper wire and the like for exciting these magnetic circuits. The STO 201 of the present invention is formed between the main magnetic pole 5 and the counter magnetic pole 6 via the main magnetic pole side magnetic field rectifying layer 12 and the counter magnetic pole magnetic field rectifying layer 13. The main magnetic pole side magnetic field rectifying layer 12 and the counter magnetic pole magnetic field rectifying layer 13 are designed so that a magnetic field as strong as possible is perpendicular to the laminated surface of the STO 201. In particular, the counter magnetic field rectifying layer 13 preferably has a narrowed structure (a cross section on the counter magnetic pole 6 side is wider than a cross section on the STO 201 side). The main magnetic pole 5 and the counter magnetic pole 6 are provided with an electrode or a means for making electrical contact with the electrode, and an STO drive current from the main magnetic pole 5 side to the counter magnetic pole 6 side or vice versa can flow through the in-plane free layer 2. It is configured as follows. The materials of the main magnetic pole 5, the main magnetic pole side magnetic field rectifying layer 12, the counter magnetic pole magnetic field rectifying layer 13, and the counter magnetic pole 6 were CoFe alloys having a large saturation magnetization and almost no magnetocrystalline anisotropy. The recording medium 7 includes a substrate 19, a laminated film in which a 10 nm-Ru layer is formed on 30 nm-CoFe as an underlayer 20, and a 7 nm-recording holding layer 24, 5 nm—a transmission layer 23, 3 nm− as a recording layer 16. A pattern medium having a resonance layer 22 equivalent to 5 Tbits per square inch (track pitch 15 nm, bit pitch 7 nm) was used. The recording holding layer 24 is CoCrPt (Hk = 2.4 MA / m), the transmission layer 23 is CoCrPt (Hk = 2.0 MA / m), the resonance layer 22 is CoCrPt (Hk = 1.6 MA / m), and the bit gap 21 Filled SiOx.

  A nonmagnetic spin scattering layer 8, an in-plane free layer 2, a nonmagnetic spin conduction layer 3, a perpendicular free layer 1, and a second nonmagnetic spin scattering layered adjacent to the main magnetic pole 5 and the main magnetic pole side magnetic field rectifying layer 12. The STO 201 made of the layer 9 is formed and reaches the counter magnetic pole 6 through the counter magnetic field rectifying layer 13. Note that the nonmagnetic spin scattering layer 8 to the second nonmagnetic spin scattering layer 9 have a columnar structure extending in the horizontal direction of the drawing and have a square shape with a cross section of 15 nm on a side. The cross-sectional shape may be a rectangular square having a long direction along the ABS surface. In the microwave assisted recording, a recording medium having a large magnetic anisotropy that cannot be recorded unless the recording magnetic field from the main magnetic pole 5 and the high-frequency magnetic field from the vertical free layer 1 and the in-plane free layer 2 are aligned is used. Therefore, the width and thickness of the main pole 5 (length in the head running direction) can be set large so that a large recording magnetic field can be obtained. In this embodiment, a recording magnetic field of about 0.7 MA / m is obtained by setting the width to 40 m and the thickness to 70 nm.

In the in-plane free layer 2, an easily magnetized plane type (Co / Fe) n multilayer film having a large saturation magnetization and a negative perpendicular magnetic anisotropy was laminated by 15 nm. For the vertical free layer 1, a 1.5 nm CoCr alloy (H _kp = 480 kA / m, B _s = 0.75T) was used. A CoCrPt alloy may be used for the vertical free layer 1. The CoCr alloy and CoCrPt alloy have a damping constant of about half that of the (Co / Ni) n multilayer film, so that the current required for oscillation can be reduced, and the material magnetic change and device characteristic deterioration due to electron migration or the like can be reduced. Can be suppressed. If a thin Co layer is inserted between the in-plane free layer 2 and the nonmagnetic spin conduction layer 3, the current required for oscillation can be further reduced. The magnetic field applied to the STO of this example is 3D because the length from the end face of the main magnetic pole side magnetic field rectifying layer 12 to the end face of the opposing magnetic pole magnetic field rectifying layer 13 is 25 nm and the height of the in-plane free layer 2 is 15 nm. When analyzed using magnetic field analysis software, it is about 1.2 MA / m (15 kOe). In the in-plane free layer 2, the magnetization rotates at a high speed in the plane along the layer, and the leakage magnetic field from the magnetic poles appearing on the ABS surface and the side surface acts as a high-frequency magnetic field.

  In the STO 201 of this embodiment, since the in-plane free layer 2 is between the main magnetic pole 5 and the vertical free layer 1, STO drive from the main magnetic pole 5 side to the counter magnetic pole 6 side to obtain the AF torque spin torque oscillation ( (DC) current needs to flow. When the magnetic flux flows from the main magnetic pole 5 side, the rotation direction of the magnetization of the in-plane free layer 2 is counterclockwise when viewed from the upstream side of the STO drive (DC) current, and the magnetic field from the main magnetic pole 5 A rotating magnetic field having the same direction as the direction of precession of magnetization of the recording medium to be reversed can be applied. When a magnetic field flows into the main magnetic pole 5, the rotation direction of the magnetization of the in-plane free layer 2 is clockwise when viewed from the upstream side of the high-frequency drive (DC) current, and is reversed by the magnetic field applied to the main magnetic pole 5. A rotating magnetic field having the same direction as the direction of precession of magnetization can be applied. Therefore, the rotating high frequency magnetic field generated from the in-plane free layer 2 has an effect of assisting the magnetization reversal by the main magnetic pole 5 regardless of the polarity of the main magnetic pole 5. This effect cannot be obtained with the high-frequency magnetic field generator of Patent Document 1 in which the direction of the spin torque does not change depending on the polarity of the main magnetic pole 5.

  As shown in the schematic diagram of FIG. 19, the magnetic head slider 102 mounted with the recording / reproducing unit 109 incorporating the STO 201 of the present invention was attached to the suspension 106, and the recording / reproducing characteristics were examined using a spin stand. Magnetic recording was performed with a head medium relative speed of 20 m / s, a magnetic spacing of 6 nm, and a track pitch of 15 nm, and this was reproduced by a GMR head having a shield interval of 13 nm. The maximum signal / noise ratio of 14.2 dB was obtained when the STO drive voltage was changed and an 1815 kFCI signal was recorded at 714 MHz when the STO drive voltage was 80 mV. In addition, when a 3630 kFCI signal was recorded at 1428 MHz, the maximum signal / noise ratio was 8.5 dB. From this, it was found that an information transfer rate exceeding 2 Gbit / s can be realized at a recording density exceeding 5 Tbits per square inch. The frequency of the high frequency magnetic field at this time was 40 GHz. When a CoFe alloy was used for the in-plane free layer 2, a sufficient signal / noise ratio could not be obtained. Since the in-plane free layer 2 of this example is a cube, it is necessary to introduce negative perpendicular magnetic anisotropy to induce in-plane magnetization rotation.

  The arrangement relationship between the magnetic head traveling direction and the recording medium will be described with reference to FIGS. 21A and 21B. There are two types of mounting modes of the magnetic head on the magnetic head slider, one is the arrangement on the trailing side shown in FIG. 21A, and the other is the arrangement on the leading side shown in FIG. 21B. Here, the trailing side and the leading side are determined by the relative moving direction of the magnetic head slider with respect to the recording medium. If the rotation direction of the recording medium is opposite to the illustrated direction, FIG. 21B is placed on the trailing side. In principle, it is possible to reverse the relationship between the trailing side and the leading side if the polarity of the spindle motor is reversed and the recording medium is rotated in the opposite direction, but the rotational speed is accurately controlled. Therefore, it is unrealistic to change the polarity of the spindle motor. When a microwave-assisted recording head using (Co / Ni) n is used for the vertical free layer of the present invention, 1 Tbit per square inch is obtained regardless of the arrangement of FIGS. 21A and 21B. A signal / noise ratio and overwrite characteristics sufficient for recording / reproduction with a recording density exceeding the above were obtained.

  22A and 22B are schematic views showing the overall configuration of the magnetic recording apparatus according to the present invention, in which FIG. 22A is a top view and FIG. 22B is an AA ′ cross-sectional view thereof. The recording medium 101 is fixed to the rotary bearing 104 and is rotated by the motor 100. FIG. 22B shows an example in which three magnetic disks and six magnetic heads are mounted. However, one or more magnetic disks and one or more magnetic heads are sufficient. The recording medium 101 has a disk shape, and recording layers are formed on both sides thereof. The slider 102 moves in a substantially radial direction on the rotating recording medium surface, and has a recording / reproducing unit at the tip. The recording / reproducing unit has a structure as shown in FIG. 19, for example, and the recording unit is provided with the main magnetic pole and the STO of the present invention.

  The suspension 106 is supported by the rotor reactor 103 via the arm 105. The suspension 106 has a function of pressing or pulling the slider 102 against the recording medium 101 with a predetermined load. A current for driving each component of the magnetic head is supplied from the IC amplifier 113 via the wiring 108. Processing of the recording signal supplied to the recording head unit and the reproduction signal detected from the reproducing head unit is executed by the read / write channel IC 112 shown in FIG. 22B. The control operation of the entire magnetic recording apparatus is realized by the processor 110 executing a disk control program stored in the memory 111. Accordingly, in this embodiment, the processor 115 and the memory 111 constitute a so-called disk controller.

  The above-described recording head and recording medium ((Co / Ni) n multilayer vertical free layer STO and CoCrPt-SiOx medium, CoCr alloy vertical free layer STO and bit pattern medium) are shown in FIG. (Each recording on each surface of a 2.5 inch magnetic disk) and performance evaluation were performed. As a result, each had a recording capacity of 2 Tbytes (1 Tbit per square inch) and an information transfer rate of 2.0 Gbit / s, and An information recording / reproducing apparatus using a high-frequency rotating magnetic field with a recording capacity of 10 Tbytes (5 Tbits per square inch) and an information transfer rate of 2.8 Gbit / s was obtained. The combination of the recording head and the recording medium is not limited to the present embodiment, and the recording head of the present invention may be combined with another recording medium. If the single dry and the (tile writing) recording method are used in combination, an information recording / reproducing apparatus having a larger capacity can be obtained. In addition, a recording head equipped with a CoCr alloy vertical free layer STO can reduce power consumption.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

1 vertical free layer 2 in-plane free layer 3 nonmagnetic spin conducting layer 5 main magnetic pole 6 counter magnetic pole 7 magnetic recording medium 8 nonmagnetic spin scattering layer 9 nonmagnetic spin scattering layer 12 main magnetic pole side magnetic field rectifying layer 13 counter magnetic pole magnetic field rectifying layer 16 Recording layer 19 Substrate 20 Underlayer 21 Bit gap 22 Resonant layer 23 Transmission layer 24 Recording holding layer 31 Fixed layer 32 FGL
DESCRIPTION OF SYMBOLS 100 Motor 101 Recording medium 102 Magnetic head slider 103 Rotary reactor 104 Rotary bearing 105 Arm 106 Suspension 108 Wiring 109 Recording / reproducing part 110 Terminal 111 Memory 112 Channel IC
113 IC amplifier 115 Processor 200 Recording head 201 STO
202 Power supply 205 Coil 206 Auxiliary magnetic pole 207 Regenerative sensor 208 Lower shield 210 Upper shield

Claims (12)

Magnetizing a magnetic recording medium by having a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, generating a magnetization reversal magnetic field from the main magnetic pole and generating a high-frequency magnetic field from the spin torque oscillation element In a magnetic recording head that records information by reversing
The spin torque oscillation element is composed of a magnetic film having a magnetic anisotropy axis perpendicular to the film surface, a perpendicular free layer whose magnetization is rotatable, and a magnetic film having an effective magnetization surface on the film surface. An in-plane free layer in which magnetization is rotatable; and a non-magnetic spin conduction layer for transmitting spin information, wherein the non-magnetic spin conduction layer is disposed between the perpendicular free layer and the in-plane free layer, A magnetic recording head, wherein an electric current is passed from an in-plane free layer side to the perpendicular free layer side.   2. The magnetic recording head according to claim 1, wherein the perpendicular free layer is thinner than the in-plane free layer.   2. The magnetic recording head according to claim 1, wherein the perpendicular free layer substantially antagonizes the magnitude of the magnetic anisotropy magnetic field caused by the material and the effective demagnetizing field in the direction perpendicular to the film surface of the perpendicular free layer in the opposite direction. A magnetic recording head characterized by the above. Magnetizing a magnetic recording medium by having a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, generating a magnetization reversal magnetic field from the main magnetic pole and generating a high-frequency magnetic field from the spin torque oscillation element In a magnetic recording head that records information by reversing
The spin torque oscillation element is composed of a magnetic film having a magnetic anisotropy axis perpendicular to the film surface, a perpendicular free layer whose magnetization is rotatable, and a magnetic film having an effective magnetization surface on the film surface. An in-plane free layer in which magnetization is rotatable, a nonmagnetic spin conduction layer that transmits spin information, a first nonmagnetic spin scattering layer that scatters spin information, and a second nonmagnetic spin scattering layer, The nonmagnetic spin-conducting layer is disposed between the perpendicular free layer and the in-plane free layer, and the first nonmagnetic spin scattering layer is opposite to the side of the perpendicular free layer facing the in-plane free layer. The second non-magnetic spin scattering layer is disposed on a side of the in-plane free layer opposite to the side facing the vertical free layer, and a current flows from the in-plane free layer side to the vertical free layer side. A magnetic recording head characterized by flowing a current.   5. The magnetic recording head according to claim 4, wherein the perpendicular free layer is thinner than the in-plane free layer.   5. The magnetic recording head according to claim 4, wherein the perpendicular free layer substantially antagonizes the magnitude of the magnetic anisotropic magnetic field caused by the material and the effective demagnetizing field in the direction perpendicular to the film surface of the perpendicular free layer in the opposite direction. A magnetic recording head characterized by the above. Magnetizing a magnetic recording medium by having a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, generating a magnetization reversal magnetic field from the main magnetic pole and generating a high-frequency magnetic field from the spin torque oscillation element In a magnetic recording head that records information by reversing
The spin torque oscillator includes a vertical free layer made of a magnetic film having a magnetic anisotropy axis in a direction perpendicular to the film surface, and an in-plane free layer made of a magnetic film having an effective magnetization surface on the film surface, A non-magnetic spin conduction layer that transmits spin information, the non-magnetic spin conduction layer being disposed between the vertical free layer and the in-plane free layer, from the in-plane free layer side to the vertical free layer side A magnetic recording head, wherein an electric current is passed, and the magnetization of the perpendicular free layer and the magnetization of the in-plane free layer rotate antiparallel to each other. 8. The magnetic recording head according to claim 7 , wherein the perpendicular free layer is thinner than the in-plane free layer. Magnetizing a magnetic recording medium by having a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, generating a magnetization reversal magnetic field from the main magnetic pole and generating a high-frequency magnetic field from the spin torque oscillation element In a magnetic recording head that records information by reversing
The spin torque oscillator includes a vertical free layer made of a magnetic film having a magnetic anisotropy axis in a direction perpendicular to the film surface, and an in-plane free layer made of a magnetic film having an effective magnetization surface on the film surface, A nonmagnetic spin transport layer that transmits spin information; a first nonmagnetic spin scattering layer that scatters spin information; and a second nonmagnetic spin scattering layer, wherein the nonmagnetic spin transport layer includes: The first nonmagnetic spin-scattering layer is disposed between the in-plane free layer and the first nonmagnetic spin-scattering layer is disposed on the opposite side of the vertical free layer from the side facing the in-plane free layer. The scattering layer is disposed on the side of the in-plane free layer opposite to the side facing the vertical free layer, and allows a current to flow from the in-plane free layer side to the vertical free layer side so that the magnetization of the vertical free layer and the surface It is characterized in that the magnetizations of the inner free layer rotate antiparallel to each other Mind the recording head. The magnetic recording head according to claim 9 , wherein the perpendicular free layer is thinner than the in-plane free layer. A magnetic recording medium; a medium driving unit that drives the magnetic recording medium; a magnetic recording head that performs a recording operation on the magnetic recording medium; and a head driving unit that positions the magnetic recording head on a desired track of the magnetic recording medium And
The magnetic recording head includes a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, and generates a magnetization reversal magnetic field from the main magnetic pole and a high frequency magnetic field from the spin torque oscillation element. Information is recorded by reversing the magnetization of the magnetic recording medium,
The spin torque oscillation element is composed of a magnetic film having a magnetic anisotropy axis perpendicular to the film surface, a perpendicular free layer whose magnetization is rotatable, and a magnetic film having an effective magnetization surface on the film surface. An in-plane free layer in which magnetization is rotatable; and a non-magnetic spin conduction layer for transmitting spin information, wherein the non-magnetic spin conduction layer is disposed between the perpendicular free layer and the in-plane free layer, A magnetic recording apparatus, wherein a current is passed from an in-plane free layer side to the vertical free layer side. A magnetic recording medium; a medium driving unit that drives the magnetic recording medium; a magnetic recording head that performs a recording operation on the magnetic recording medium; and a head driving unit that positions the magnetic recording head on a desired track of the magnetic recording medium And
The magnetic recording head includes a main magnetic pole and a spin torque oscillation element disposed in the vicinity of the main magnetic pole, and generates a magnetization reversal magnetic field from the main magnetic pole and a high frequency magnetic field from the spin torque oscillation element. Information is recorded by reversing the magnetization of the magnetic recording medium,
The spin torque oscillation element is composed of a magnetic film having a magnetic anisotropy axis perpendicular to the film surface, a perpendicular free layer whose magnetization is rotatable, and a magnetic film having an effective magnetization surface on the film surface. An in-plane free layer in which magnetization is rotatable, a nonmagnetic spin conduction layer that transmits spin information, a first nonmagnetic spin scattering layer that scatters spin information, and a second nonmagnetic spin scattering layer, The nonmagnetic spin-conducting layer is disposed between the perpendicular free layer and the in-plane free layer, and the first nonmagnetic spin scattering layer is opposite to the side of the perpendicular free layer facing the in-plane free layer. The second non-magnetic spin scattering layer is disposed on a side of the in-plane free layer opposite to the side facing the vertical free layer, and a current flows from the in-plane free layer side to the vertical free layer side. A magnetic recording apparatus characterized by flowing a current.

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