# Patent

## Title
NiFeX-based seed layer for magnetic recording media

## Abstract

A recording medium having improved signal-to-noise ratio (SNR) capabilities includes a NiFeX-based magnetic seed layer over a soft magnetic underlayer, where X comprises an element that is soluble in and has a higher melting point than Ni. X may be selected from a group of elements, including ruthenium (Ru), which may facilitate growth of smaller grains and distributions in the corresponding magnetic recording layer(s).

## Background
FIELD OF EMBODIMENTS
Embodiments of the invention may relate generally to hard disk drives and more particularly to magnetic recording media.
BACKGROUND
A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces. When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head that is positioned over a specific location of a disk by an actuator. A read/write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. Write heads make use of the electricity flowing through a coil, which produces a magnetic field. Electrical pulses are sent to the write head, with different patterns of positive and negative currents. The current in the coil of the write head induces a magnetic field across the gap between the head and the magnetic disk, which in turn magnetizes a small area on the recording medium.
In order to improve the recording performance for media, it is desirable to increase the SNR (Signal-to-Noise Ratio) through structure design and materials selections.
Any approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.



BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
FIG. 1 is a plan view illustrating a hard disk drive, according to an embodiment;
FIG. 2 illustrates a perpendicular magnetic recording (PMR) media stack, according to an embodiment;
FIG. 3 is a plan view illustrating grains of magnetic recording media, according to an embodiment;
FIG. 4 is a histogram graph illustrating grain center-to-center distribution of magnetic recording media of FIG. 3, according to an embodiment; and
FIG. 5 is a flow diagram illustrating a method of manufacturing a recording medium, according to an embodiment.



DETAILED DESCRIPTION
Approaches to a recording medium having a NiFeX-based magnetic seed layer under a magnetic recording layer are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. It will be apparent, however, that the embodiments described herein may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments described herein.
Physical Description of Illustrative Operating Environments
Embodiments may be used in the context of a perpendicular magnetic recording (PMR) medium for a hard-disk drive (HDD) data storage device. Thus, in accordance with an embodiment, a plan view illustrating an HDD 100 is shown in FIG. 1 to illustrate an exemplary operating environment.
FIG. 1 illustrates the functional arrangement of components of the HDD 100 including a slider 110b that includes a magnetic-reading/recording head 110a. Collectively, slider 110b and head 110a may be referred to as a head slider. The HDD 100 includes at least one head gimbal assembly (HGA) 110 including the head slider, a lead suspension 110c attached to the head slider typically via a flexure, and a load beam 110d attached to the lead suspension 110c. The HDD 100 also includes at least one magnetic-recording medium 120 rotatably mounted on a spindle 124 and a drive motor (not visible) attached to the spindle 124 for rotating the medium 120. The head 110a includes a write element and a read element for respectively writing and reading information stored on the medium 120 of the HDD 100. The medium 120 or a plurality of disk media may be affixed to the spindle 124 with a disk clamp 128.
The HDD 100 further includes an arm 132 attached to the HGA 110, a carriage 134, a voice-coil motor (VCM) that includes an armature 136 including a voice coil 140 attached to the carriage 134 and a stator 144 including a voice-coil magnet (not visible). The armature 136 of the VCM is attached to the carriage 134 and is configured to move the arm 132 and the HGA 110, to access portions of the medium 120, being mounted on a pivot-shaft 148 with an interposed pivot-bearing assembly 152. In the case of an HDD having multiple disks, the carriage 134 is called an “E-block,” or comb, because the carriage is arranged to carry a ganged array of arms that gives it the appearance of a comb.
An assembly comprising a head gimbal assembly (e.g., HGA 110) including a flexure to which the head slider is coupled, an actuator arm (e.g., arm 132) and/or load beam to which the flexure is coupled, and an actuator (e.g., the VCM) to which the actuator arm is coupled, may be collectively referred to as a head stack assembly (HSA). An HSA may, however, include more or fewer components than those described. For example, an HSA may refer to an assembly that further includes electrical interconnection components. Generally, an HSA is the assembly configured to move the head slider to access portions of the medium 120 for read and write operations.
With further reference to FIG. 1, electrical signals (e.g., current to the voice coil 140 of the VCM) comprising a write signal to and a read signal from the head 110a, are provided by a flexible interconnect cable 156 (“flex cable”). Interconnection between the flex cable 156 and the head 110a may be provided by an arm-electronics (AE) module 160, which may have an on-board pre-amplifier for the read signal, as well as other read-channel and write-channel electronic components. The AE 160 may be attached to the carriage 134 as shown. The flex cable 156 is coupled to an electrical-connector block 164, which provides electrical communication through electrical feedthroughs provided by an HDD housing 168. The HDD housing 168, also referred to as a base, in conjunction with an HDD cover provides a sealed, protective enclosure for the information storage components of the HDD 100.
Other electronic components, including a disk controller and servo electronics including a digital-signal processor (DSP), provide electrical signals to the drive motor, the voice coil 140 of the VCM and the head 110a of the HGA 110. The electrical signal provided to the drive motor enables the drive motor to spin providing a torque to the spindle 124 which is in turn transmitted to the medium 120 that is affixed to the spindle 124. As a result, the medium 120 spins in a direction 172. The spinning medium 120 creates a cushion of air that acts as an air-bearing on which the air-bearing surface (ABS) of the slider 110b rides so that the slider 110b flies above the surface of the medium 120 without making contact with a thin magnetic-recording layer in which information is recorded.
The electrical signal provided to the voice coil 140 of the VCM enables the head 110a of the HGA 110 to access a track 176 on which information is recorded. Thus, the armature 136 of the VCM swings through an arc 180, which enables the head 110a of the HGA 110 to access various tracks on the medium 120. Information is stored on the medium 120 in a plurality of radially nested tracks arranged in sectors on the medium 120, such as sector 184. Correspondingly, each track is composed of a plurality of sectored track portions (or “track sector”), for example, sectored track portion 188. Each sectored track portion 188 may be composed of recorded data and a header containing a servo-burst-signal pattern, for example, an ABCD-servo-burst-signal pattern, which is information that identifies the track 176, and error correction code information. In accessing the track 176, the read element of the head 110a of the HGA 110 reads the servo-burst-signal pattern which provides a position-error-signal (PES) to the servo electronics, which controls the electrical signal provided to the voice coil 140 of the VCM, enabling the head 110a to follow the track 176. Upon finding the track 176 and identifying a particular sectored track portion 188, the head 110a either reads data from the track 176 or writes data to the track 176 depending on instructions received by the disk controller from an external agent, for example, a microprocessor of a computer system.
Introduction
A perpendicular magnetic recording (PMR) system records data as magnetizations oriented perpendicular to the plane of the magnetic recording disk. The magnetic disk has a magnetically soft underlayer covered by a thin magnetically hard top layer. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where it is sufficiently spread out and weak that it will not erase the signal recorded by the write pole when it passes back through the magnetically hard top layer on its way back to the return pole.
Perpendicular recording media may comprise a stack of several Co based magnetic layers, which is grown on a Ru intermediate layer or a combination of Ru and Ru—X intermediate layers, a Ni—W or Ni—W—Al or Ni—W—Al—Fe orientation control seed layer, a possible Ta seed layer, and soft magnetic underlayers on a substrate, in that order. If glass substrates are used, Cr or CrTi or CrTa adhesion layers may also be present underneath the soft magnetic underlayers. In the foregoing media design structure, the Ni-based orientation control seed layer, which is poly-crystalline, primarily sets the template for the grain size and its distribution in the Ru based intermediate layer and subsequently, in the Co based magnetic layer. The grains in poly-crystalline thin films grow by means of two events: (i) nucleation of grains at energetically favorable sites on the underlying layer or substrate, and (ii) once nucleated, grain growth is driven by diffusion processes. During thin film sputtering, since both nucleation and grain growth events happen simultaneously, a log-normal grain size distribution results. Nucleation is a thermodynamic process and is typically a random event that can be controlled to some extent by engineering pre-determined nucleation sites on the underlying layer or substrate. Grain growth, however, is a kinematical process and is governed by the mobility of the precipitate (sputtered atoms that have nucleated into grains). The latter process provides the context for embodiments described herein.
FIG. 2 illustrates a perpendicular magnetic recording (PMR) media stack, according to an embodiment. Media stack 202 comprises a substrate 202, over which an antiferromagnetically coupled soft magnetic underlayer (AFC-SUL) 204 laminate is fabricated, over which one or more seed layer 206 is fabricated, over which an intermediate layer 208 is fabricated, over which one or more magnetic recording layer 210 is fabricated, and over which an overcoat is fabricated. Further, and for example, one or more adhesion layer may be fabricated on the substrate 202.
Reference herein to a “layer” is not intended to be thereby limited to a single layer, rather each “layer” referenced may actually comprise multiple layers, or a “stack” of thin film layers. Further, the term “fabricated” may include any of a number of thin film processes, such as chemical and/or physical deposition processes (of which sputtering is commonly used in hard disk media production), which “grow” grains of poly-crystalline thin films, for example, as well as crystalline epitaxial growth, and the like. Therefore, use of the term “fabricated” and related terms are not limited to any particular process, unless otherwise indicated.
For example and according to an embodiment, media stack 200 may comprise a Al—Mg substrate 202 covered by (i) Cr or CrTa or CrTi adhesion layers, (ii) an antiferromagnetically coupled soft magnetic underlayer (AFC-SUL 204) laminate, (iii) a Ta based seed layer and a NiW or NiWAl or NiWAlFe based seed layer (seed layer 206), (iv) a Ru and/or RuCo based intermediate layer (intermediate layer 208), and (v) a stack of several magnetic layers (magnetic recording layer 210), including exchange-control layers (ECLs) or exchange-break layers (EBLs), covered with a carbon overcoat (overcoat 212). Such a media stack may use a exchange-coupled composite (ECC) design, including two exchange-break layers. According to an embodiment, intermediate layer 208 comprises dual Ru intermediate layers, comprising a Ru layer processed at low Ar gas sputter pressure of  ̃7 mtorr, followed by another Ru layer processed using high Ar gas sputter pressure of  ̃90 mtorr.
NiX-Based Seed Layer
In order to further increase areal storage densities from current levels, tighter grain sizes and distributions are highly desireable in the Co based magnetic recording layer. This is from the point of view of reducing noise (i.e., improving the signal-to-noise ratio, or SNR) not only by creating more uniform grain morphologies, but also by reducing inter-granular magnetic interactions. One way to achieve tighter grain size distributions in the magnetic recording layer is to improve the grain size distributions in the Ni based seed layer itself, since the latter acts as a template for the former. With that in mind, the grain growth process may be controlled to some extent based on the sputtering of the Ni based seed layer.
As mentioned, the grain growth process is a mobility driven event, thereby determined by the diffusion coefficient of the precipitate, which itself depends inversely on the melting point of the precipitate. Basis for the inverse relationship between the melting point and the diffusion coefficient for an element may be found in, e.g., “Correlations For Diffusion Constants” by A. M. Brown and M. F. Ashby, from Acta Metallurgica, Vol. 28, pp. 1085-1101, the entire contents of which is incorporated by reference in its entirety for all purposes as if fully set forth herein. Section 2.1 of the foregoing paper may be particularly relevant.
In order to control the mobility of the precipitate, it is deemed beneficial to alloy the Ni seed material with elements that are both soluble in Ni and have higher melting points compared to Ni. The precipitates formed by sputtering this alloy seed material can be expected to have higher melting points compared to the original seed, and consequently lower diffusion coefficients.
The diffusion coefficient, or diffusivity, is typically described in the context of a relationship among at least two elements or substances, i.e., one with respect to another, and may be described in units of length/time (e.g., nm2/s). Thus, the lower the diffusivity of one substance with respect to the other, the slower the substances diffuse into each other. Consequently, this could lead to tighter grain size distributions in the seed, and subsequently in the magnetic recording layer, further leading to improved recording performance.
Continuing, the diffusion coefficient is the measure of mobility of diffusing species and, including in solids at different temperatures, is generally found to be well-predicted by Arrhenius plots. The diffusion coefficient may be characterized with the following equation:

D=D0 exp{−Qd/RT};  (1)

where

D is the diffusion coefficient (m2/s);

D0 is the temperature-independent preexponential (m2/s);

Qd is the activation energy for diffusion (J/mol or eV/atom);

R is the gas constant (8.31 J/mol-K or 8.62×10−5 eV/atom-K); and

T is the absolute temperature (K).

The above equation (1) can be rewritten as:

ln D=ln D0−(Qd/R)(1/T); or  (2)

log D=log D0−(Qd/2.3R)(1/T).  (3)

The activation energy Qd and preexponential D0, therefore, can be estimated by plotting ln D versus 1/T or log D versus 1/T, where such plots are aforementioned Arrhenius plots.

According to an embodiment, seed layer 206 comprises a magnetic NiFe-based seed layer. According to an embodiment, seed layer 206 comprises a NiFeX-based seed layer where X comprises an element that is soluble in Ni and has a higher melting point than Ni.
Table 1 presents a list of chemical elements that are soluble in nickel (Ni), up to approximately x at %, and have a higher melting point than nickel.










TABLE 1







Element X
x Atomic %









Ruthenium (Ru)
0-35 at %



Osmium (Os)
0-10 at %



Platinum (Pt)
0-30 at %



Rhenium (Re)
0-15 at %



Rhodium (Rh)
0-40 at %



Technetium (Tc)
0-30 at %



Iridium (Ir)
0-15 at %



Cobalt (Co)
0-60 at %










According to an embodiment, seed layer 206 comprises a magnetic (NiFe)100-x(X)x alloy with X being selected from a group consisting of Ruthenium (Ru), Osmium (Os), Platinum (Pt), Rhenium (Re), Rhodium (Rh), Technetium (Tc), Iridium (Ir), and Cobalt (Co). According to a related embodiment, seed layer 206 comprises a magnetic (NiFe)100-x(X)x alloy with X being selected from a group consisting of Ruthenium (x=0-35 at %), Osmium (x=0-10 at %), Platinum (x=0-30 at %), Rhenium (x=0-15 at %), Rhodium (x=0-40 at %), Technetium (x=0-30 at %), Iridium (x=0-15 at %), and Cobalt (x=0-60 at %).
For a non-limiting example, seed layer material of the compositions Ni-3W-1Al-30Fe-(x at %)Ru, where x=3 and 6, were evaluated. According to published phase diagrams of the Ni—Ru binary alloy, pure Ni has a melting point (m.p.) of 1455° C., whereas pure Ru has a m.p. of 2334° C., and the solid solubility of Ru in Ni is around 5 at %. The published phase diagram is for a state of thermodynamic equilibrium, however, during sputtering of a single phase NiRu-based thin film alloy, the phases are typically meta-stable, i.e., not in thermodynamic equilibrium, therefore higher solubility of Ru in Ni is achievable. Therefore, the foregoing “up to approximately x at %” ( ̃x atomic percentage) of the different elements listed in Table 1 are deemed producible using current state-of-the-art sputtering tools and processes by controlling the sputter parameters accordingly, for example, the temperature and pressure. During sputtering, an alloy of Ni & Ru in the limit of solid solubility can be expected to form a precipitate with (i) a higher melting point compared to pure Ni precipitate, and (ii) a secondary phase structure that is insoluble in Ni and forms a grain boundary phase. Both properties of the precipitate can help to control the grain growth and grain segregation processes.
Thus, and according to an embodiment, seed layer 206 comprises a NiFeRu-based seed layer. According to a related embodiment, seed layer 206 comprises a NiFeRu-based seed layer comprising around 1-20 at % Ru. As discussed and as presented in Table 1, a NiFeRu-based alloy having a range up to 35 at % Ru is deemed producible, however, a range considered practical yet effective in a high-volume production environment is approximately 1-20 at % Ru.
As discussed in reference to FIG. 2, one or more seed layer 206 is fabricated over the soft magnetic underlayer (AFC-SUL) 204 laminate. According to an embodiment, the NiFeX-based magnetic seed layer is formed in direct contact with the soft magnetic underlayer.
Magnetic Grain Size, Uniformity, Segregation
To repeat, the grain growth process is a mobility driven event, thereby determined by the diffusion coefficient of the precipitate, which itself depends inversely on the melting point of the precipitate. In order to control the mobility of the precipitate, it is deemed beneficial to alloy the Ni seed material with elements that are both soluble in Ni and have higher melting points compared to Ni, as the precipitates formed by sputtering this alloy seed material (e.g., NiX) can be expected to have higher melting points compared to the original seed (e.g., Ni), and consequently lower diffusion coefficients, as well as a secondary phase structure that is insoluble in Ni and forms a grain boundary phase. These characteristics help to control the grain growth and grain segregation processes, thereby leading to tighter grain size distributions and intra-granular segregation in the seed, and consequently in the magnetic recording layer(s).
FIG. 3 is a plan view illustrating grains of magnetic recording media, according to an embodiment. FIG. 3 shows plan view images of the grains from magnetic recording medium taken using a Transmission Electron Microscope (TEM), from (a) medium using a Ni-3W-1Al-30Fe seed and (b) from medium using a Ni-3W-1Al-30Fe-6Ru seed, according to an embodiment. The average center-to-center distance between grains in the case of the (a) seed was 8.5±1.7 nm and in the case of the (b) seed the average center-to-center distance between grains was 7.9±1.5 nm. The grain center-to-center dispersion was 20.6% in the case of the (a) seed, and was about 19.4% in the case of the (b) seed. Thus, when the Ni-3W-1Al-30Fe-6Ru seed was introduced, not only did the grain center-to-center distance shrink, but the dispersion also became smaller.
FIG. 4 is a histogram graph illustrating grain center-to-center distribution of the magnetic recording media of FIG. 3, according to an embodiment. This histogram points to the conclusion that the medium on the Ni-3W-1Al-30Fe-6Ru seed (image (b) of FIG. 3) has few large grains (e.g., >9 nm in center-to-center distance) compared to the medium on the Ni-3W-1Al-30Fe seed (image (a) of FIG. 3). Resultantly, the average center-to-center distance and the dispersion were both lower for the (b) seed in comparison to the (a) seed, which highlights improvements facilitated by the NiFeRu-based seed material. A practical result illustrated by the lower average center-to-center distance and by the lower grain-to-grain center dispersion of the magnetic grains of the magnetic recording layer (e.g., magnetic recording layer 210 of FIG. 2) is that the magnetic grains are smaller (e.g., as evidenced by a lower average center-to-center distance) and more uniform in size (e.g., as evidenced by a lower grain-to-grain center dispersion) for a magnetic recording layer grown using the NiFeX-based seed material than would a magnetic recording layer grown on a NiFe-based seed layer not comprising the X element.
A comparison of the coercivity and of the demagnetization factor of the magnetic recording media of FIG. 3(a) and FIG. 3(b), for a single magnetic layer configuration, showed that the medium using the Ni-3W-1Al-30Fe-6Ru seed layer (image (b) of FIG. 3) demonstrated lower coercivities over a range of thicknesses, compared to medium using Ni-3W-1Al-30Fe seed layer (image (a) of FIG. 3). Further, for seed layer thicknesses> ̃4 nm, the demagnetization factor is larger for the medium using the Ni-3W-1Al-30Fe-6Ru seed layer. Therefore, while the coercivities may be lower when using the Ni-3W-1Al-30Fe-6Ru seed layer, the inter-granular exchange coupling interactions are also reduced favorably (i.e., inter-granular segregation improved), which leads to an improvement in SNR performance.
A comparison of the coercivity and of the thermal stability factor of the magnetic recording media of FIG. 3(a) and FIG. 3(b), for a multiple magnetic layer stack (exchange-coupled composite media design), showed that the medium using the Ni-3W-1Al-30Fe-6Ru seed layer (image (b) of FIG. 3) demonstrated lower coercivities and thermal stability factors over a range of thicknesses, compared to medium using Ni-3W-1Al-30Fe seed layer (image (a) of FIG. 3). Therefore, this is an indication that the grains of the magnetic recording layer may be smaller when using the Ni-3W-1Al-30Fe-6Ru seed.
Embodiments described herein may be directed to a PMR media design utilizing a NiFeX-based magnetic seed layer for reduced noise and likewise improved SNR. In various embodiments, the introduction of a suitable seed layer results in a desirable decrease in the magnetic grain size and an increase in grain size uniformity, and more uniform inter-granular segregation, and a corresponding increase in the SNR for the PMR media. However, embodiments are not limited to PMR technology only, as embodiments may be implemented in the context of other types of magnetic recording media.
Method of Manufacturing Recording Media
FIG. 5 is a flow diagram illustrating a method of manufacturing a recording medium, according to an embodiment. Embodiments may be implemented in a PMR hard disk drive including such PMR media. Fabrication of the media stack described herein may be through implementation of a sputtering process using a sputtering system using a NiX sputtering target for the seed layer, for example.
At block 502, at least one antiferromagnetically exchange coupled magnetically soft underlayer laminate is formed over a substrate. For example, AFC-SUL 204 (FIG. 2) is formed over substrate 202 (FIG. 2).
At block 504, a NiFeX-based magnetic seed layer is formed over the soft underlayer, where X comprises an element having a higher melting point than Ni. For example, a NiFeX-based seed layer 206 (FIG. 2) is formed over the AFC-SUL 204 (FIG. 2). According to an embodiment, a NiFeRu-based seed layer is formed over the AFC-SUL. According to a related embodiment, the NiFeRu-based seed layer formed at block 504 comprises a NiFeRu-based seed layer comprising around 1-20 at % Ru. As discussed and as presented in Table 1, a NiFeRu-based alloy having a range up to 35 at % Ru is deemed producible, however, a range considered practical yet effective in a high-volume production environment is approximately 1-20 at % Ru.
According to an embodiment, the NiFeX-based seed layer formed at block 504 comprises a magnetic (NiFe)100-x(X)x alloy with X being selected from a group consisting of Ruthenium (Ru), Osmium (Os), Platinum (Pt), Rhenium (Re), Rhodium (Rh), Technetium (Tc), Iridium (Ir), and Cobalt (Co). According to a related embodiment, the NiFeX-based seed layer formed at block 504 comprises a magnetic (NiFe)100-x(X)x alloy with X being selected from a group consisting of Ruthenium (x=0-35 at %), Osmium (x=0-10 at %), Platinum (x=0-30 at %), Rhenium (x=0-15 at %), Rhodium (x=0-40 at %), Technetium (x=0-30 at %), Iridium (x=0-15 at %), and Cobalt (x=0-60 at %).
At block 506, at least one magnetic recording layer is formed over the NiFeX-based magnetic seed layer. For example, a magnetic recording layer 208 (FIG. 2) stack is formed over the NiFeX-based seed layer 206 (FIG. 2).
The deposition of the various layers referenced in FIG. 5 can be performed using a variety of deposition sub-processes, for non-limiting examples, physical vapor deposition (PVD), sputter deposition and ion beam deposition, and chemical vapor deposition (CVD) including plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD) and atomic layer chemical vapor deposition (ALCVD). Furthermore, other suitable deposition techniques known in the art may also be used.
Extensions and Alternatives
In the foregoing description, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. Therefore, various modifications and changes may be made thereto without departing from the broader spirit and scope of the embodiments. Thus, the sole and exclusive indicator of what is the invention, and is intended by the applicants to be the invention, is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. Hence, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
In addition, in this description certain process steps may be set forth in a particular order, and alphabetic and alphanumeric labels may be used to identify certain steps. Unless specifically stated in the description, embodiments are not necessarily limited to any particular order of carrying out such steps. In particular, the labels are used merely for convenient identification of steps, and are not intended to specify or require a particular order of carrying out such steps.

## Claims

1. A recording medium comprising:
a substrate;
at least one soft magnetic underlayer;
a NiWAlFeX-based magnetic seed layer over said soft magnetic underlayer; and
at least one magnetic recording layer over said NiWAlFeX-based magnetic seed layer;
wherein X comprises an element that is soluble in Ni and has a higher melting point than Ni and is from a group consisting of osmium (Os), platinum (Pt), rhenium (Re), rhodium (Rh), technetium (Tc), and iridium (Ir).

2. The recording medium of claim 1, wherein X comprises an element from a group consisting of osmium (1-10 at %), platinum (1-30 at %), rhenium (1-15 at %), rhodium (1-40 at %), technetium (1-30 at %), and iridium (1-15 at %).

3. The recording medium of claim 1, wherein said NiWAlFeX-based magnetic seed layer is formed in direct contact with said soft magnetic underlayer.

4. The recording medium of claim 1, wherein said soft magnetic underlayer is an antiferromagnetically exchange coupled soft magnetic underlayer laminate.

5. The recording medium of claim 1, wherein X is selected such that NiX has a lower diffusion coefficient in WAlFe than the diffusion coefficient of Ni in WAlFe.

6. The recording medium of claim 1, wherein said magnetic recording layer comprises smaller magnetic grains than would a magnetic recording layer grown on a NiFe-based seed layer not comprising X.

7. The recording medium of claim 1, wherein said magnetic recording layer comprises magnetic grains more uniform in size than would a magnetic recording layer grown on a NiFe-based seed layer not comprising X.

8. The recording medium of claim 1, wherein said magnetic recording layer comprises more uniform magnetic grain segregation than would a magnetic recording layer grown on a NiFe-based seed layer not comprising X.

9. A data storage device comprising:
a magnetic recording disk medium rotatably mounted on a spindle, said disk medium comprising:
a substrate,
at least one soft magnetic underlayer,
a NiWAlFeX-based magnetic seed layer over said soft magnetic underlayer, and
at least one magnetic recording layer over said NiWAlFeX-based magnetic seed layer,
wherein X comprises an element that is soluble in Ni and has a higher melting point than Ni and is from a group consisting of osmium (Os), platinum (Pt), rhenium (Re), rhodium (Rh), technetium (Tc), and iridium (Ir);

a head slider comprising a magnetic write head configured to write to said disk medium; and
a voice coil motor configured to move said head slider to access portions of said disk medium.

10. The data storage device of claim 9, wherein X comprises an element from a group consisting of osmium (1-10 at %), platinum (1-30 at %), rhenium (1-15 at %), rhodium (1-40 at %), technetium (1-30 at %), and iridium (1-15 at %).

11. The data storage device of claim 9, wherein X is selected such that NiX has a lower diffusion coefficient in WalFe than the diffusion coefficient of Ni in WAlFe.

12. The data storage device of claim 9, wherein said magnetic recording layer of said disk medium comprises smaller magnetic grains than would a magnetic recording layer grown on a NiFe-based seed layer not comprising X.

13. The data storage device of claim 9, wherein said magnetic recording layer of said disk medium comprises magnetic grains more uniform in size than would a magnetic recording layer grown on a NiFe-based seed layer not comprising X.

14. The data storage device of claim 9, wherein said magnetic recording layer of said disk medium comprises more uniform magnetic grain segregation than would a magnetic recording layer grown on a NiFe-based seed layer not comprising X.

15. A method of manufacturing a recording medium, the method comprising:
forming at least one antiferromagnetically exchange coupled magnetically soft underlayer laminate over a substrate;
forming a NiWAlFeX-based magnetic seed layer over said at least one magnetically soft underlayer, wherein X comprises an element that has a higher melting point than Ni and is from a group consisting of osmium (Os), platinum (Pt), rhenium (Re), rhodium (Rh), technetium (Tc), and iridium (Ir); and
forming at least one magnetic recording layer over said NiWAlFeX-based magnetic seed layer.

16. The method of claim 15, wherein forming said NiWAlFeX-based magnetic seed layer includes forming a NiWAlFeX-based magnetic seed layer wherein X comprises an element from a group consisting of osmium (1-10 at %), platinum (1-30 at %), rhenium (1-15 at %), rhodium (1-40 at %), technetium (1-30 at %), and iridium (1-15 at %).

17. A recording medium comprising:
a substrate;
at least one soft magnetic underlayer;
a NiWAlFeRu-based magnetic seed layer over said soft magnetic underlayer and comprising 15-20 atomic percent (at %) Ru; and
at least one magnetic recording layer over said NiWAlFeRu-based magnetic seed layer.