Patent Description:
Embodiments of the present disclosure generally relate to a microwave assisted magnetic recording (MAMR) write head with a spin torque oscillator (STO) device and a high damping trailing shield seed layer.

The heart of the functioning and capability of a computer is the storing and writing of data to a data storage device, such as a hard disk drive (HDD). The volume of data processed by a computer is increasing rapidly. There is a need for higher recording density of a magnetic recording medium to increase the function and the capability of a computer.

In order to achieve higher recording densities, such as recording densities exceeding <NUM> Tbit/in<NUM> for a magnetic recording medium, the width and pitch of write tracks are narrowed, and thus the corresponding magnetically recorded bits encoded in each write track is narrowed. One challenge in narrowing the width and pitch of write tracks is decreasing a surface area of a main pole of the magnetic write head at a media facing surface. As the main pole becomes smaller, the writing field becomes smaller as well, limiting the effectiveness of the magnetic write head.

Heat-assisted magnetic recording (HAMR) and microwave assisted magnetic recording (MAMR) are two types of energy-assisted recording technology to improve the recording density of a magnetic recording medium, such as a HDD. In MAMR, a spin torque oscillator (STO) device is located next to or near the write element in order to produce a high-frequency AC field, such as in a microwave frequency band. The high-frequency AC field reduces an effective coercivity of a magnetic recording medium used to store data and allows writing of the magnetic recording medium at lower magnetic writing fields emanated from the write pole. Thus, higher recording density of the magnetic recording medium may be achieved by MAMR technology. However, a hard disk drive system with a MAMR write head may have an undesirable high level of bit-flipping of the magnetic medium. Therefore, there is a need in the art for an improved MAMR write heads. <CIT>, over which independent claim <NUM> is characterised, discloses a magnetic media drive employing a magnetic recording head including a MAMR stack.

A microwave assisted magnetic recording (MAMR) write head includes a main pole and a trailing shield. A spin torque oscillator device is disposed between the main pole and the trailing shield. The spin torque oscillator device includes a free layer. A trailing shield hot seed layer is disposed between the spin torque oscillator device and the trailing shield. The trailing shield hot seed layer includes a magnetic material doped with a rare earth element. The trailing shield hot seed layer includes the rare earth element in an atomic percent content from about <NUM>% to about <NUM>% atomic percent, or the trailing shield hot seed layer has an intrinsic damping from about <NUM> to about <NUM>.

In the following, reference is made to embodiments of the disclosure. However, it should be understood that the disclosure is not limited to specific described embodiments but limited by the claims.

The terms "over," "under," "between," "on", and other similar terms as used herein refer to a relative position of one layer with respect to other layers. As such, for example, one layer disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between layers may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first layer "on" a second layer is in contact with the second layer. The relative position of the terms does not define or limit the layers to a vector space orientation of the layers.

The term "comprises/comprising" includes the subset meaning of "consists/consisting essentially of" and includes the subset meaning of "consists/consisting of.

The invention comprises a spin torque oscillator (STO) device for a microwave assisted magnetic recording (MAMR) write head disposed in a trailing shield gap between a main pole and a trailing shield (TS). The TS includes a high damping TS hot seed layer. The free layer of the STO device of the MAMR head oscillates during writing to provide an assistive AC field. However, the free layer may also cause oscillations of the magnetization direction with other components of the MAMR write head. These oscillations may generate additional AC fields which may cause increased bit flipping at the magnetic medium at areas proximate the MAMR recording point and/or diminish the assisting AC field at the MAMR recording point. A lower magnetic moment (Ms) and high damping in the TS hot seed layer reduces an AC field proximate the TS hot seed layer and reducing bit flipping in comparison to a low damping TS hot seed layer.

<FIG> is a schematic illustration of certain embodiments of a magnetic media drive including a magnetic write head, such as a MAMR head. Such magnetic media drive may be a single drive/device or comprise multiple drives/devices. For the ease of illustration, a single disk drive <NUM> is shown according to one embodiment. The disk drive <NUM> includes at least one rotatable magnetic disk <NUM> supported on a spindle <NUM> and rotated by a drive motor <NUM>. The magnetic recording on each magnetic disk <NUM> is in the form of any suitable patterns of data tracks, such as annular patterns of concentric data tracks (not shown) on the magnetic disk <NUM>.

At least one slider <NUM> is positioned near the magnetic disk <NUM>. Each slider <NUM> supports a head assembly <NUM> including one or more read/write heads, such as a MAMR head including a STO device. As the magnetic disk <NUM> rotates, the slider <NUM> moves radially in and out over the disk surface <NUM> so that the head assembly <NUM> may access different tracks of the magnetic disk <NUM> where desired data are written. Each slider <NUM> is attached to an actuator arm <NUM> by way of a suspension <NUM>. The suspension <NUM> provides a slight spring force which biases the slider <NUM> toward the disk surface <NUM>. Each actuator arm <NUM> is attached to an actuator <NUM>. The actuator <NUM> as shown in <FIG> may be a voice coil motor (VCM). The VCM includes a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by control unit <NUM>.

During operation of the disk drive <NUM>, the rotation of the magnetic disk <NUM> generates an air or gas bearing between the slider <NUM> and the disk surface <NUM> which exerts an upward force or lift on the slider <NUM>. The air or gas bearing thus counter-balances the slight spring force of suspension <NUM> and supports slider <NUM> off and slightly above the disk surface <NUM> by a small, substantially constant spacing during normal operation.

The various components of the disk drive <NUM> are controlled in operation by control signals generated by control unit <NUM>, such as access control signals and internal clock signals. Typically, the control unit <NUM> comprises logic control circuits, storage means and a microprocessor. The control unit <NUM> generates control signals to control various system operations such as drive motor control signals on line <NUM> and head position and seek control signals on line <NUM>. The control signals on line <NUM> provide the desired current profiles to optimally move and position slider <NUM> to the desired data track on disk <NUM>. Write and read signals are communicated to and from the head assembly <NUM> by way of recording channel <NUM>. Certain embodiments of a magnetic media drive of <FIG> may further include a plurality of media, or disks, a plurality of actuators, and/or a plurality number of sliders.

<FIG> is a schematic illustration of certain embodiments of a cross sectional side view of a head assembly <NUM> facing the magnetic disk <NUM> or other magnetic storage medium. The head assembly <NUM> may correspond to the head assembly <NUM> described in <FIG>. The head assembly <NUM> includes a media facing surface (MFS) <NUM> facing the disk <NUM>. As shown in <FIG>, the magnetic disk <NUM> relatively moves in the direction indicated by the arrow <NUM> and the head assembly <NUM> relatively moves in the direction indicated by the arrow <NUM>.

In some embodiments, the head assembly <NUM> includes a magnetic read head <NUM>. The magnetic read head <NUM> may include a sensing element <NUM> disposed between shields S1 and S2. In certain embodiments, the sensing element <NUM> is a magnetoresistive (MR) sensing element, such an element exerting a tunneling magneto-resistive (TMR) effect, a magneto-resistance (GMR) effect, an extraordinary magneto-Resistive (EMR) effect, or a spin torque oscillator (STO) effect. The magnetic fields of magnetized regions in the magnetic disk <NUM>, such as perpendicular recorded bits or longitudinal recorded bits, are detectable by the sensing element <NUM> as the recorded bits.

The head assembly <NUM> includes a MAMR write head <NUM>. The MAMR write head <NUM> includes a main pole <NUM>, a leading shield <NUM>, a TS <NUM>, and a spin torque oscillator (STO) device <NUM> disposed between the main pole <NUM> and the TS <NUM>. The main pole <NUM> serves as a first electrode and has a front portion at the MBS.

The main pole <NUM> comprises a magnetic material, such as CoFe, CoFeNi, or FeNi, other suitable magnetic materials. In certain embodiments, the main pole <NUM> comprises small grains of magnetic materials in a random texture, such as body-centered cubic (BCC) materials formed in a random texture. For example, a random texture of the main pole <NUM> may be formed by electrodeposition. The MAMR write head <NUM> includes a coil218 around the main pole <NUM> that excites the main pole <NUM> producing a writing magnetic field structures for affecting a magnetic medium of the rotatable magnetic disk <NUM>. The coil <NUM> may be a helical structure or one or more sets of pancake structures.

In certain embodiments, the main pole <NUM> includes a trailing taper <NUM> and a leading taper <NUM>. The trailing taper <NUM> extends from a location recessed from the MFS <NUM> to the MFS <NUM>. The leading taper <NUM> extends from a location recessed from the MFS <NUM> to the MFS <NUM>. The trailing taper <NUM> and the leading taper <NUM> may have the same degree or different degree of taper with respect to a longitudinal axis <NUM> of the main pole <NUM>. In some embodiments, the main pole <NUM> does not include the trailing taper <NUM> and the leading taper <NUM>. Instead, the main pole <NUM> includes a trailing side (not shown) and a leading side (not shown) in which the trailing side and the leading side are substantially parallel.

The TS <NUM> comprises a magnetic material, such as FeNi, or other suitable magnetic materials, serving as a second electrode and return pole for the main pole <NUM>. The leading shield <NUM> may provide electromagnetic shielding and is separated from the main pole <NUM> by a leading gap <NUM>.

The STO device <NUM> is positioned proximate the main pole <NUM> and reduces the coercive force of the magnetic medium, so that smaller writing fields can be used to record data. An electron current is applied to STO device <NUM> from a power source <NUM> to produce a microwave field. The electron current may be a direct current (DC) waveforms, pulsed DC waveforms, and/or pulsed current waveforms going to positive and negative voltages, or other suitable waveforms.

In certain embodiments, the STO device <NUM> may be electrically coupled to the main pole <NUM> and the TS <NUM> in which the main pole <NUM> and the TS are separated by an insulating layer <NUM>. The power source <NUM> may provide electron current to the STO device <NUM> through the main pole <NUM> and the TS <NUM>. For direct current or pulsed current, the power source <NUM> may flow electron current from the main pole <NUM> through the STO device <NUM> to the TS <NUM> or may flow electron current from the TS <NUM> through the STO device <NUM> to the main pole <NUM> depending on the orientation of the STO device <NUM>. In other embodiments, the STO device <NUM> may be coupled to electrical leads providing an electron current other than from the main pole and/or the TS.

<FIG> is a schematic illustration of certain embodiments of a plan view of a media facing surface of the MAMR write head <NUM> of <FIG> with a STO device <NUM> between a main pole <NUM> and a TS <NUM> in the track direction. The main pole <NUM> of the write head <NUM> may be any suitable shape (i.e., trapezoidal, triangular, etc.) and suitable dimensions. The STO device <NUM> may be formed to any suitable shape, any suitable dimension, and any suitable position between the main pole <NUM> and the TS <NUM>. For example, the width 230W of the STO device <NUM> may be greater than, equal to, or less than the width 220W of the main pole <NUM> at the interface with the STO device <NUM>.

The leading shield <NUM> may be positioned on one or more sides of the main pole <NUM> with the leading gap <NUM> therebetween. A side gap <NUM> may be positioned on the sides of the STO device <NUM>. The side gap <NUM> may comprise an insulating material.

The track direction is label as the x-coordinate and the cross-track direction is labeled as the x-coordinate. The perpendicular direction to the media facing surface would be the z-coordinate into/out of the X-Y plane.

<FIG> are side cross-sectional views of various embodiments of a STO device <NUM> of a MAMR write head <NUM> configured to oscillate due to spin-transfer torque. The MAMR write head <NUM> can be the MAMR write head of <FIG> or other suitable MAMR write heads. The STO device <NUM> is positioned proximate the main pole <NUM> and reduces the coercive force of the magnetic disk <NUM> or other magnetic storage medium magnetic medium, so that smaller writing fields (HWriting Field) can be used to record data. A bias current (ISTO) applied to the STO device <NUM> from the power source <NUM> of <FIG> produces an assisting AC field (HAssisting Field), such as a microwave field. The assisting AC field is formed by oscillation of the magnetization of a field generation layer (FGL) or free layer <NUM> of the STO device <NUM>. The chirality or rotation direction of the free layer <NUM> switches in response to the switch in direction of the writing field of the main pole <NUM>.

In certain embodiments, as shown in <FIG>, the STO device <NUM> includes a seed layer <NUM> over or on the main pole <NUM>, a free layer <NUM> over or on the seed layer <NUM>, a spacer layer <NUM> over or on the free layer <NUM>, a high damping TS hot seed layer <NUM> over or on the spacer layer <NUM>, and a TS <NUM> over the high damping TS hot seed layer <NUM>. Electron current flow from the main pole <NUM> through the STO device <NUM> to the TS <NUM> causes polarized electrons to be reflected from the TS <NUM> back towards the free layer <NUM>. The reflected polarized electrons creates spin transfer torque on the magnetization of the free layer <NUM> and causes the magnetization of the free layer <NUM> to oscillate.

In certain embodiments, as shown in <FIG>, the STO device <NUM> includes a spacer layer <NUM> over or on the main pole <NUM>, a free layer <NUM> over or on the spacer layer <NUM>, a capping layer <NUM> over or on the free layer <NUM>, a high damping TS hot seed layer <NUM> over or on the capping layer <NUM>, and a TS <NUM> over the TS hot seed layer <NUM>. Electron current flow from the TS <NUM> through the STO device <NUM> to the main pole <NUM> causes polarized electrons to be reflected from the main pole <NUM> back towards the free layer <NUM>. The reflected polarized electrons creates spin transfer torque on the magnetization of the free layer <NUM> and causes the magnetization of the free layer <NUM> to oscillate.

In certain embodiments, as shown in <FIG>, the STO device <NUM> includes a seed layer <NUM> over or on the main pole <NUM>, a spin polarization layer (SPL) <NUM> over or on the seed layer <NUM>, a spacer layer <NUM> over or on the SPL <NUM>, a free layer <NUM> over or on the spacer layer <NUM>, a capping layer <NUM> over or on the free layer <NUM>, a high damping TS hot seed layer <NUM> over or on the capping layer <NUM>, and a TS <NUM> over or on the high damping TS hot seed layer <NUM>. Electron current flow from the main pole <NUM> through the STO device <NUM> to the TS <NUM> imparts spin polarization of the electrons from the SPL <NUM>. The polarized electrons from the SPL <NUM> creates spin transfer torque on the magnetization of the free layer <NUM> and causes the magnetization of the free layer <NUM> to oscillate. The TS <NUM> may reflect polarized electrons towards the free layer <NUM> to increase spin-transfer torque on the free layer <NUM>.

In certain embodiments, as shown in <FIG>, the STO device <NUM> includes a first spacer layer 440A over or on the main pole <NUM>, a free layer <NUM> over or on the first spacer layer <NUM>, a second spacer layer 440B over or on the free layer <NUM>, a spin polarization layer (SPL) <NUM> over or on the second spacer layer 440B, a capping layer <NUM> over or on the SPL <NUM>, a high damping TS hot seed layer <NUM> over or on the capping layer <NUM>, and a TS <NUM> over or on the high damping TS hot seed layer <NUM>. Electron current flow from the TS <NUM> through the STO device <NUM> to the main pole <NUM> imparts spin polarization of the electrons from the SPL <NUM>. The polarized electrons from the SPL <NUM> creates spin transfer torque on the magnetization of the free layer <NUM> and causes the magnetization of the free layer <NUM> to oscillate. The main pole <NUM> may reflect polarized electrons towards the free layer <NUM> to increase spin-transfer torque on the free layer <NUM>.

In certain embodiments, the free layer <NUM> of the STO device <NUM> of <FIG> comprises one or more magnetic alloy layers comprising Fe, Co, FeCo, NiFe, CoFeAl, CoFeGe, CoMnGe, CoFeSi, CoMnSi, and other magnetic materials. For example, in certain embodiments, the free layer <NUM> comprises a ferromagnetic material having a high moment and high spin polarization, such as FeCo and FeCo alloys.

In certain embodiments, the spacer layer(s) <NUM> of the STO device <NUM> of <FIG> includes one or more non-magnetic conductive materials, such as Au, Ag, Al, Cu, AgSn, NiAl, other non-magnetic conductive materials, alloys thereof, or multiple layers thereof. The spacer layer <NUM> may be made of a material having a high spin transmissivity for spin torque transfer on the free layer <NUM>.

In certain embodiments, the SPL <NUM> of the STO device <NUM> of <FIG> or <FIG> comprises NiFe, CoFe, CoFeNi, CoMnGe, NiCo, NiFeCu, CoFeMnGe, CoMnSi, CoFeSi, other soft or hard ferromagnetic materials, other Heusler alloys, other suitable magnetic layers, or multiple layers thereof. The SPL <NUM> can comprise a material having magnetic anisotropy oriented in any general direction, such as perpendicular, angled, or longitudinal, to the plane of the magnetic disk <NUM> or other magnetic recording medium.

In certain embodiments, the seed layer <NUM> of the STO device <NUM> of <FIG> or <FIG> comprises ruthenium, copper, tantalum, other non-magnetic materials, alloys thereof, or multiple layers thereof. In certain embodiments, the seed layer <NUM> resets or provides a texture break for the growth of the SPL <NUM> with low structural defects over the seed layer <NUM>. Low structural defects of the SPL <NUM> results in the SPL <NUM> with more magnetic homogeneity, lower critical current for reversal of the SPL <NUM>, and better yield in the formation of the SPL <NUM>. For example, a seed layer comprising tantalum over copper provides a nano-crystalline structure formed over the random texture of the main pole <NUM>. The nano-crystalline structure provides a smooth surface for formation of structured layers or crystalline layers thereover with low structure/crystal defects. In certain embodiments, the seed layer <NUM> provides a surface for good growth of structured and/or crystalline layers such, such as face centered cubic (FCC) metal alloys, body center cubic (BCC) metal alloys, and ordered phase alloys. For example, a seed layer <NUM> comprising ruthenium has a hexagonal close packed structure. The hexagonal close packed (HCP) structure provides a good template surface for growth or interfacing with a FCC layer, a BCC layer, or a Heusler layer with low structural defects. In certain embodiments, the seed layer <NUM> removes spin polarization of electrons from the main pole <NUM>.

In certain embodiments, a capping layer <NUM> of the STO device <NUM> of <FIG> or <FIG> comprises one or more layers of non-magnetic conductive materials, metals or metal alloys of Ru, Ir, Ta, Ti, and other non-magnetic metals. The capping layer <NUM> may protects the STO device <NUM> during formation of the STO device and formation of the MAMR write head <NUM>, such as during deposition, annealing, patterning, cleaning, etc..

In certain embodiments, a notched structure may be formed over the TS hot seed layer <NUM> or the TS hot seed layer <NUM> and the TS <NUM> may be formed into a pedestal structure (collectively referred to as a notched trailing shield). A notched trailing shield can reflect polarized electrons towards the free layer <NUM> to increase spin-transfer torque on the free layer <NUM>, such as in the STO devices of <FIG> and <FIG>.

The high damping TS hot seed layer <NUM> of the STO device <NUM> of <FIG> comprises a magnetic material doped with one or more rare earth metals. Examples of magnetic materials include CoFe and CoFe alloys. Rare earth metals include holmium (Ho), dysprosium (Dy), terbium (Tb), samarium (Sm), other rare earth metals, or combinations thereof. One particular example of a high damping TS hot seed layer <NUM> is CoFeHo.

The damping in the TS hot seed layer is impacted by certain magnetic materials in combination with certain doping materials. In certain embodiments, the TS hot seed layer <NUM> comprises an atomic percent content of a rare earth metal from about <NUM>% to about <NUM>%. A high damping TS hot seed layer <NUM> having a rare earth metal content of greater than <NUM>% may be undesirable since the rare earth metal content excessively reduces the magnetic moment (Bs) of the TS hot seed layer, reducing the write field gradient and/or causes the TS hot seed layer to be susceptible to corrosion during manufacture and/or during operation. A high damping TS hot seed layer <NUM> having a rare earth metal content of less than <NUM>% may be undesirable since a certain damping may not be achieved to reduce oscillation of the TS hot seed layer caused by oscillation of the free layer <NUM>.

In certain embodiments, the TS hot seed layer <NUM> has an intrinsic damping from about <NUM> to about <NUM>. The intrinsic damping in a magnetic system (a thin film, multilayer stack, or structure device) is a physical property of the magnetic system. The damping in the TS hot seed layer of a MAMR write head is determined by isolating the TS hot seed layer or by creating a like sample of the TS hot seed layer and measuring the intrinsic damping in the isolated TS hot seed layer or like sample of the TS hot seed layer by ferromagnetic resonance (FMR) measurements at <NUM> utilizing a PhaseFMR tool available from NanOsc Instruments AB located in Kista, Sweden. Intrinsic damping, also called Gilbert damping, is a unitless parameter determined from the Landau-Lifschitz-Gilbert equation. An intrinsic damping of greater than <NUM> may be undesirable since the magnetic moment (Bs) of the TS hot seed layer may be too low and may reduce the write field gradient. An intrinsic damping of less than <NUM> may be undesirable since a certain damping may not be achieved to reduce oscillation of the TS hot seed layer caused by oscillation of the free layer <NUM>.

<FIG> is a schematic diagram of a MAMR writer head, such as the MAMR writer head <NUM> of <FIG>. The main pole <NUM> is energized in a magnetization direction 220A by the write coil <NUM> which causes the TS hot seed layer <NUM> to be in a magnetization direction 235A. Current applied to the STO device <NUM> causes the magnetization direction 450A of the free layer <NUM> to oscillate. Oscillation of the free layer <NUM> causes oscillation of the TS hot seed layer <NUM>. The oscillation of the hot seed layer generates an additional AC field proximate the hot seed layer. When the TS hot seed layer comprises a low damping material, the additional AC field proximate the TS hot seed layer may be relatively large, such as greater than <NUM> Oe in a perpendicular direction to the media facing surface, which may inadvertently cause bit flipping in the magnetic medium, such as inadvertent writing to or inadvertent erasure of the magnetic medium. When TS hot seed layer <NUM> comprises a high damping material, the additional AC field proximate the TS hot seed layer is reduced, such as to <NUM> Oe or less, to about <NUM> Oe or less, in a perpendicular direction. This reduces bit flipping in the magnetic medium, such as reducing inadvertent writing to and/or inadvertent erasure of the magnetic medium.

By minimizing amplitude of oscillations of a TS hot seed layer, the contribution of an AC field from the hot seed layer can be reduced. Doping the TS hot seed layer with a rare earth metal reduces the amplitude of oscillations of the TS hot seed layer by lowering the magnetic moment (Ms) of the TS hot seed layer and by providing high damping in the TS hot seed layer.

The certain embodiments, a microwave assisted magnetic recording (MAMR) write head includes a main pole and a trailing shield. A spin torque oscillator device is disposed between the main pole and the trailing shield. The spin torque oscillator device includes a free layer. A trailing shield hot seed layer is disposed between the spin torque oscillator device and the trailing shield. The trailing shield hot seed layer includes a magnetic material doped with a rare earth element. In certain embodiments, the trailing shield hot seed layer includes the rare earth element in an atomic percent content from about <NUM>% to about <NUM>% atomic percent. In certain embodiments, the trailing shield hot seed layer has an intrinsic damping from about <NUM> to about <NUM>.

<FIG> is a graph of the amplitudes of the AC fields of an STO device with a TS hot seed layer without high damping along a down-track position starting from the main pole area (-<NUM>) to the TS hot seed area (+<NUM>). The amplitudes of the AC fields were measured by the magnetic field strength in a down track field (hd), in a cross track field (hc), and in a perpendicular field to a media facing surface (hp). Measurements were conducted at a frequency of <NUM>. The TS hot seed without high damping comprised CoFe with an intrinsic damping (αint) of <NUM>. The STO device had an AC field with a perpendicular component of about <NUM> Oe in the TS hot seed area.

<FIG> is a graph of the amplitudes of the AC fields of an STO device with a TS hot seed layer with high damping along a down-track position starting from the main pole area (-<NUM>) to the TS hot seed area (+<NUM>). The amplitudes of the AC fields were measured by the magnetic field strength in a down track field (hd), in a cross track field (hc), and in a perpendicular field to a media facing surface (hp). Measurements were conducted at a frequency of <NUM>. The TS hot seed with high damping comprised CoFeHo with an intrinsic damping (αint) of <NUM>. The STO device had an AC field with a perpendicular component of about <NUM> Oe in the TS hot seed area.

Claim 1:
A microwave assisted magnetic recording (MAMR) write head (<NUM>), comprising:
a main pole (<NUM>) and a trailing shield (<NUM>); and
a spin torque oscillator device (<NUM>) disposed between the main pole and the trailing shield;
wherein the spin torque oscillator device (<NUM>) comprises a free layer (<NUM>); and in that the microwave assisted magnetic recording write head further comprises:
a trailing shield hot seed layer (<NUM>) disposed between the spin torque oscillator device (<NUM>) and the trailing shield (<NUM>), characterized by
the trailing shield hot seed layer comprising a magnetic material doped with a rare earth element; wherein:
the trailing shield hot seed layer (<NUM>) comprises the rare earth element in an atomic percent content of between <NUM>% and <NUM>% atomic percent; and/or
the trailing shield hot seed layer (<NUM>) has intrinsic damping of between <NUM> and <NUM>.