Patent Application
20160099017
The present invention relates to data storage systems, and more particularly, this invention relates to a layered segregant materials configured to improve magnetic grain shape in heat assisted magnetic recording (HAMR) media.
The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
However, the further miniaturization of the various components, particularly, the size and/or pitch of magnetic grains, presents its own set of challenges and obstacles in conventional products. Noise performance and spatial resolution are key parameters in magnetic recording media and are ongoing challenges to advance the achievable areal density of media. The dominant media noise source today is transition jitter. In sputtered media, it reflects the finite size, random positioning and dispersions in size, orientation and magnetic properties of the fine grains that comprise the media.
HAMR, also referred to as thermally assisted magnetic recording, has emerged as a promising magnetic recording technique to address grain size and transition jitter. As the coercivity of the ferromagnetic recording material is temperature dependent, HAMR employs heat to lower the effective coercivity of a localized region of the magnetic media and write data therein. The data state becomes stored, or “fixed,” upon cooling the magnetic media to ambient temperatures (i.e., normal operating temperatures typically in a range between about 15° C. and 60° C.). Heating the magnetic media may be accomplished by a number of techniques such as directing electromagnetic radiation (e.g. visible, infrared, ultraviolet light, etc.) onto the magnetic media surface via focused laser beams or near field optical sources. HAMR techniques may be applied to longitudinal and/or perpendicular recording systems, although the highest density storage systems are more likely to be perpendicular recording systems.
HAMR thus allows use of magnetic recording materials with substantially higher magnetic anisotropy and smaller thermally stable grains as compared to conventional magnetic recording techniques. Moreover, to further increase the areal density of magnetic recording media, granular magnetic recording materials may be utilized. Granular magnetic recording materials typically include a plurality of magnetic grains separated by one or more segregants, which aid in limiting the lateral exchange coupling between the magnetic grains. These segregants may influence magnetic properties, the size and shape of the magnetic grains, the exchange coupling strength between the magnetic grains, the grain boundary width, etc.
According to one embodiment, a magnetic recording medium includes a substrate, and a magnetic recording layer structure positioned above the substrate, the magnetic recording layer structure including: a first magnetic recording layer having a first plurality of magnetic grains surrounded by a first segregant; a second magnetic recording layer positioned above the first magnetic recording layer, the second magnetic recording layer having a second plurality of magnetic grains surrounded by a second segregant; and a third magnetic recording layer positioned above the second magnetic recording layer, the third magnetic recording layer having a third plurality of magnetic grains surrounded by a third segregant, where at least the first segregant is primarily a combination of carbon and a second component, and where the second segregant is primarily carbon.
According to another embodiment, a magnetic recording medium includes a substrate, and a magnetic recording layer structure positioned above the substrate, the magnetic recording layer structure including: a first magnetic recording layer having a first plurality of magnetic grains surrounded by a first segregant; a second magnetic recording layer positioned above the first magnetic recording layer, the second magnetic recording layer having a second plurality of magnetic grains surrounded by a second segregant; and a third magnetic recording layer positioned above the second magnetic recording layer, the third magnetic recording layer having a third plurality of magnetic grains surrounded by a third segregant, where the second segregant is different from the first segregant and/or the third segregant.
Any of these embodiments may be implemented in a magnetic data storage system such as a disk drive system, which may include a magnetic head, a drive mechanism for passing a magnetic medium (e.g., hard disk) over the magnetic head, and a controller electrically coupled to the magnetic head.
Other aspects and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings.
TEM image of a FePt-C/FePt-C magnetic recording bilayer structure.
The following description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations.
Unless otherwise specifically defined herein, ail terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc.
It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified.
As also used herein, the term “about” denotes an interval of accuracy that ensures the technical effect of the feature in question. In various approaches, the term “about” when combined with a value, refers to plus and minus 10% of the reference value. For example, a thickness of about 10 nm refers to a thickness of 10 nm±1 nm.
The following description discloses several preferred embodiments of magnetic recording storage systems and/or related systems and methods, as well as operation and/or component parts thereof. For example, various embodiments disclosed herein include magnetic recording media having multilayered magnetic recording layers with different segregant materials. In particular approaches, the magnetic recording layers disclosed herein may include at least three magnetic layers, each having a carbon based segregant. Material components may be introduced to these carbon based segregates thereby improving the grain shape in addition to the magnetic properties of the magnetic medium.
In one general embodiment, a magnetic recording medium includes a substrate, and a magnetic recording layer structure positioned above the substrate, the magnetic recording layer structure including: a first magnetic recording layer having a first plurality of magnetic grains surrounded by a first segregant; a second magnetic recording layer positioned above the first magnetic recording layer, the second magnetic recording layer having a second plurality of magnetic grains surrounded by a second segregant; and a third magnetic recording layer positioned above the second magnetic recording layer, the third magnetic recording layer having a third plurality of magnetic grains surrounded by a third segregant, where at least the first segregant is primarily a combination of carbon and a second component, and where the second segregant is primarily carbon.
In another general embodiment, a magnetic recording medium includes a substrate, and a magnetic recording layer structure positioned above the substrate, the magnetic recording layer structure including: a first magnetic recording layer having a first plurality of magnetic grains surrounded by a first segregant; a second magnetic recording layer positioned above the first magnetic recording layer, the second magnetic recording layer having a second plurality of magnetic grains surrounded by a second segregant; and a third magnetic recording layer positioned above the second magnetic recording layer, the third magnetic recording layer having a third plurality of magnetic grains surrounded by a third segregant, where the second segregant is different from the first segregant and/or the third segregant.
Referring now to
As shown in
At least one slider 113 is positioned near the disk 112, each slider 113 supporting one or more magnetic read/write portions 121, e.g., of a magnetic head according to any of the approaches described and/or suggested herein. As the disk rotates, slider 113 is moved radially in and out over disk surface 122 so that portions 121 may access different tracks of the disk where desired data are recorded and/or to be written. Each slider 113 is attached to an actuator arm 119 by means of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator 127. The actuator 127 as shown in
During operation of the disk storage system, the rotation of disk 112 generates an air bearing between slider 113 and disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation. Note that in some embodiments, the slider 113 may slide along the disk surface 122.
The various components of the disk storage system are controlled in operation by control signals generated by controller 129, such as access control signals and internal clock signals. Typically, control unit 129 comprises logic control circuits, storage (e.g., memory), and a microprocessor. In a preferred approach, the control unit 129 is electrically coupled (e.g., via wire, cable, line, etc.) to the one or more magnetic read/write portions 121, for controlling operation thereof. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position slider 113 to the desired data track on disk 112. Read and write signals are communicated to and from read/write portions 121 by way of recording channel 125.
The above description of a typical magnetic disk storage system, and the accompanying illustration of
An interface may also be provided for communication between the disk drive and a host (integral or external) to send and receive the data and for controlling the operation of the disk drive and communicating the status of the disk drive to the host, all as will be understood by those of skill in the art.
In a typical head, an inductive write portion includes a coil layer embedded in one or more insulation layers (insulation stack), the insulation stack being located between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write portion. The pole piece layers may be connected at a back gap. Currents are conducted through the coil layer, which produce magnetic fields in the pole pieces. The magnetic fields fringe across the gap at the ABS for the purpose of writing bits of magnetic field information in tracks on moving media, such as in circular tracks on a rotating magnetic disk.
The second pole piece layer has a pole tip portion which extends from the ABS to a flare point and a yoke portion which extends from the flare point to the back gap. The flare point is where the second pole piece begins to widen (flare) to form the yoke. The placement of the flare point directly affects the magnitude of the magnetic field produced to write information on the recording medium.
As shown in the magnetic head 200 of
Perpendicular writing is achieved by forcing flux through the stitch pole 208 into the main pole 206 and then to the surface of the disk positioned towards the ABS 218.
In various optional approaches, the magnetic head 200 may be configured for HAMR. Accordingly, for HAMR operation, the magnetic head 200 may include a heating mechanism of any known type to heat the magnetic medium (not shown). For instance, as shown in
An optional heater is shown in
Moreover, in various optional approaches, the piggyback magnetic head 201 may also be configured for heat assisted magnetic recording (HAMR). Thus, for HAMR operation, the magnetic head 200 may additionally include a light source 230 (e.g., a laser) that illuminates a near field transducer 232 of known type via a waveguide 234.
Referring now to
As shown in
Layer 310 may be comprised of a suitable light transmitting material, as would be known by one of reasonable skill in the relevant art. Exemplary materials include Ta2O5, and/or TiO2. As shown, the core layer 310 has approximately uniform cross section along its length. As well known in the art, the optical waveguide can have a number of other possible designs including a planar solid immersion mirror or planar solid immersion lens which have a non-uniform core cross section along the waveguide's length.
In various approaches, coil layers (not shown) and various insulating and spacer layers (not shown) might reside in the cavity bounded by the ABS, back-gap(s) 304, lower return pole 302, and/or upper bounding layers 306, 308, and 312 as would be recognized by those of skill in the art. Layers 302, 304, 306, and 308 may be comprised of a suitable magnetic alloy or material, as would be known by one of reasonable skill in the relevant art. Exemplary materials include Co, Fe, Ni, Cr and combinations thereof.
As described above,
With continued reference to
In various optional approaches, the recording/playback head 406 may additionally be configured for heat assisted magnetic recording (HAMR). Accordingly, for HAMR operation, the recording/playback head 406 may include a heating mechanism of any known type to heat, and thus lower the effective coercivity, of a localized region on the magnetic medium 400 surface in the vicinity of the main pole 410. For instance, as shown in
Improvements in longitudinal recording media have been limited due to issues associated with thermal stability and recording field strength. Accordingly, pursuant to the current push to increase the areal recording density of recording media, perpendicular recording media (PMR) has been developed and found to be superior to longitudinal recording media.
The orientation of magnetic impulses in the magnetic recording layer 506 is substantially perpendicular to the surface of the recording layer. The magnetization of the soft magnetic underlayer 504 is oriented in (or parallel to) the plane of the soft magnetic underlayer 504. As particularly shown in
As noted above, the magnetization of the soft magnetic underlayer 504 is oriented in (parallel to) the plane of the soft magnetic underlayer 504, and may represented by an arrow extending into the paper. However, as shown in
It should be again noted that in various approaches, the perpendicular head 508 may be configured for heat assisted magnetic recording (HAMR). Accordingly, for HAMR operation, the perpendicular head 508 may include a heating mechanism of any known type to heat, and thus lower the effective coercivity of, a localized region on the magnetic media surface in the vicinity of the main pole 518. For instance, as shown in
Except as otherwise described herein with reference to the various inventive embodiments, the various components of the structures of
As discussed previously, HAMR allows magnetic recording technology to use materials with substantially larger magnetic anisotropy (e.g., small thermally stable grains are possible) and coercive field by localized heating of the magnetic layer above its Curie temperature, where anisotropy is reduced. One example of a magnetic recording material having a particularly high magnetic anisotropic constant, and thus particularly suitable for HAMR purposes, is a chemically ordered L10 FePt alloy. A chemically-ordered L10 FePt alloy, in its bulk form, is known as a face-centered tetragonal (FCT) L10-ordered phase material (also called a CuAu material). The c-axis of the L10 phase is the easy axis of magnetization and is oriented perpendicular to the disk substrate.
Chemical ordering in a FePt alloy is achieved by deposition thereof at elevated temperatures (about 450 to about 700° C.). However elevated deposition temperature of a granular FePt magnetic recording layer may result in unwanted grain joining, coalescence and surface roughening and thus deteriorate the layer's microstructure and magnetic properties. One or more segregants may thus be added to a L10 FePt based magnetic recording layer to isolate the L10 FePt magnetic grains.
In one embodiment, a magnetic recording layer may include a plurality of L10 FePt magnetic grains surrounded, and thereby isolated, by a carbon segregant. The carbon segregant may be present in the magnetic recording layer in an amount ranging from about 20 at % to about 50 at %, in some approaches. However, formation of a L10 FePt-C magnetic recording layer via sputtering at about 600 to about 650° C. results in spherical L10 FePt magnetic grains, which may undesirably limit the thickness of the magnetic recording layer at an average grain diameter (e.g., in the range from about 6 nm to about 8 nm) and thus impose a serious limitation on the signal strength of said layer. Moreover, a L10 FePt-C magnetic recording layer may also be rough, having a bimodal L10 FePt magnetic grain size distribution comprised of larger grains (with grain diameters ranging from about 6 nm to about 8 nm) and thermally unstable smaller grains (with grain diameters less than about 3 nm).
Attempts to form cylindrical or columnar magnetic grains, which are particularly applicable to perpendicular magnetic recording purposes, may involve partially or completely replacing the aforementioned carbon segregant in a L10 FePt based magnetic recording layer with one or more oxides, according to another embodiment. Suitable oxides may include TiO2, SiO2AlO2, Al2O3, MgO, Ta2O5, B2O3, or other oxide as would become apparent to one skilled in the art upon reading the present disclosure. In comparison to a L10 FePt-C magnetic recording layer, a L10 FePt-oxide magnetic recording layer may have reduced roughness and a more columnar magnetic grain shape. However, inclusion of one or more oxide segregants in a L10 FePt based magnetic recording layer may ultimately compromise (i.e., degrade) the magnetic properties of the layer. For instance, replacing a carbon segregant with one or more oxide segregants in a L10 FePt based magnetic recording layer may drop the coercivity, Hc, from values of up to about 5.2 Teslas does to values below about 0.1 Tesla. Without wishing to be bound by any particular theory, it is believed that this drop in coercivity may be due to the partial oxidation of the L10 FePt, and/or to the partial incorporation of portions of the oxide segregant into the L10 FePt magnetic grains.
In yet another embodiment aimed at forming cylindrical or columnar magnetic grains, the aforementioned carbon segregant in a L10 FePt based magnetic recording layer may be partially and/or completely replaced with one or more non-oxide segregants. Non-oxide segregants may include AlN, TaN, W, Ti, BN, SiNx, SiNx+C, or other suitable non-oxide segregants that become apparent to one having ordinary skill in the art upon reading the present disclosure. In one particular approach, a L10 FePt based magnetic recording layer may include a BN segregant. However, despite optimization of growth conditions (e.g., pressure, deposition temperature, growth rate, etc.), the thickness of the L10 FePt-BN magnetic recording layer is still limited. Moreover, the coercivity of the L10 FePt-BN magnetic recording layer may drop to values as low as about 1.5 Tesla, as compared to a L10 FePt-C magnetic recording layer with a coercivity around about 4.5 Tesla to about 5.2 Tesla. A coercivity of about 1.5 Tesla is better than the coercivity of about 0.1 Tesla or less achieved using an oxide segregant, yet still insufficient for good HAMR magnetic recording media. Accordingly, while a non-oxide segregant in a L10 FePt based magnetic recording layer may impart less of a spherical shape on the magnetic grains as compared to a carbon segregant, a non-oxide segregant may also undesirably degrade the magnetic properties of said magnetic recording layer.
In other embodiments, a magnetic recording layer may include a L10 FePtX alloy surrounded by any of the aforementioned segregants (e.g., C, an oxide segregant, a non-oxide segregant etc.), where X is a material configured to optimize (e.g., reduce) the growth and/or Curie temperature associated with the magnetic recording layer. Suitable materials for X may include Ag, Cu, Au, Ni, Mn, Pd, and other materials that would become apparent to one skilled in the art upon reading the present disclosure. However, a magnetic recording layer including a L10 FePtX alloy with a carbon, oxide and/or non-oxide segregant may still exhibit unwanted magnetic grain size distributions, magnetic grain shapes and magnetic properties. For example, a sputtered 6 nm thick L10 FePtAg-C (35 at %) film produces spherical magnetic grains and bimodal distribution of magnetic grain sizes.
Referring now to
As shown in
The magnetic recording medium 700 also includes an adhesion layer 706 positioned above the substrate layer 704. In various approaches, the adhesion layer 706 may comprise Ni, Ta, Ti, and/or alloys thereof. In preferred approaches, the adhesion layer may comprise an amorphous material that does not affect the crystal orientation of the layers deposited thereon.
The magnetic recording medium 700 additionally includes a heat dissipating (heat sink) layer 708 positioned above the adhesion layer 706. The heat sink layer 708, which may include a material having a high thermal conductivity (e.g., greater than 30 W/m-K, preferably greater than 100 W/m-K), may be particularly useful for HAMR purposes. For instance, the heat sink layer 708 is configured to allow heat deposited in one or more magnetic layers positioned thereabove to quickly dissipate and limits lateral heat flow in said magnetic layer(s), thus introducing directional vertical heat flow, which allows for a small heat spot and high thermal gradient during recording. In various approaches, this heat sink layer 708 may be a plasmonic layer. Suitable materials for the heat sink layer 708 may include, but are not limited to Ta, Ti, Cr, Fe, Cu, Ag, Pt, Au, Cr, Mo, etc. and alloys thereof.
The magnetic recording medium 700 further includes a seed layer 710 positioned above the heat sink layer 708. The seed layer 710 may act as a texture defining layer, e.g., configured to influence the epitaxial growth of the magnetic recording layers 712, 714 formed thereabove. In some approaches, the seed layer 710 may include MgO, TiN, MgTiOx, SrTiOx, TiC, MgFeOx etc. or suitable seed layer materials as would become apparent to one skilled in the art upon reading the present disclosure. In more approaches, the seed layer 710 may have a bilayer structure, e.g., with a lower CrRu layer and an upper Pt layer on the CrRu layer,
While not shown in
It is important to note that in some approaches, the magnetic recording medium 700 may include the heat sink layer 708 and a soft magnetic underlayer, both of which may be positioned between the adhesion layer 706 and the seed layer 710. In approaches where both a soft magnetic underlayer and a heat sink layer 708 are present, the soft magnetic underlayer may be positioned above or below the heat sink layer 708, as equivalent effects may be provided regardless of the position of the soft magnetic underlayer relative to the heat sink layer 708.
As also shown in
The magnetic recording layers 712, 714 may be formed using a sputtering process. According to one approach, the magnetic grain material(s) and one or more segregant component(s) may be sputtered from the same target; however, in another approach, the magnetic grain material(s) and/or segregant components) may be sputtered from different, respective targets. The magnetic grain and segregant materials are preferably deposited onto the magnetic recording medium 700 at the same time, in a heated environment, e.g., from about 400 degrees to about 800° C. in approaches where at least one granular chemically ordered L10 FePt magnetic recording layer is desired.
To facilitate a conformal growth of the first and second magnetic recording layers 712, 714, an etching step is preferably (but not necessarily) performed on each of the respective magnetic layers after they are formed. Thus, an etching step may be used to define the upper surface of each of the magnetic layers and expose the material of the magnetic layer, e.g., before an additional layer is formed there above. According to various approaches, the etching step may include an Inductively Coupled Plasma (ICP) etch step, etc. or any other etching process that would become apparent to one skilled in the art upon reading the present disclosure.
Accordingly, the magnetic grains 720 of the second magnetic recording layer 714 may be physically characterized by growth directly on the magnetic grains 716 of the first magnetic recording layer 712, which may primarily be due to the etching step noted above. Thus, each of the magnetic grains 720 of the second magnetic recording layer 714 that are formed directly above the magnetic grains 716 of the first magnetic recording layer 712 may form a larger composite magnetic grain 724 that extends along the total thickness, t, of the magnetic recording bilayer structure 702.
In some approaches, the total thickness, t, of the magnetic recording bilayer structure 702 may be between about 2 nm to about 20 nm. In more approaches, each of the two magnetic recording layers 712, 714 may have a respective thickness t1, t2 from about 1 nm to about 10 nm, preferably about 6 nm. Moreover, the thicknesses t1 and t2 may be the same or different in various approaches.
In numerous approaches, an average pitch, P, (center-to-center spacing) of the magnetic grains 716, 720 in the first and/or second magnetic recording layers 712, 714 may be in a range from about 5 nm to about 11 nm, but could be higher or lower depending on the desired application. Furthermore, an average diameter, d, of the magnetic grains 716, 720 in the first and/or second magnetic recording layers 712, 714 may preferably be in a range from about 4 nm to about 10 nm, but could be higher or lower depending on the desired application.
In preferred approaches, the magnetic grains 724 (e.g., each of which is comprised of a magnetic grain 720 of the second magnetic recording layer 714 that is positioned directly above a magnetic grain 716 of the first magnetic recording layer 712) have an average aspect ratio (i.e., total thickness, t, to diameter, d) of about 1.2, but could be higher or lower depending on the desired application.
In some approaches, the magnetic grains 716 of the first magnetic recording layer 712 and/or the magnetic grains 720 of the second magnetic recording layer 714 may include chemically ordered L10 FePt. In more approaches, the magnetic grains 716 of the first magnetic recording layer 712 and/or the magnetic grains 720 of the second magnetic recording layer 714 may include chemically ordered L10 FePtX, where X may include one or more of Ag, Cu, Au, Ni, Mn, Pd, etc. In various approaches, the magnetic grains 716 of the first magnetic recording layer 712 may include one or more materials that are the same or different from the materials comprising the magnetic grains 720 of the second magnetic recording layer 714.
In additional approaches, the first segregant 718 of the first magnetic recording layer 712 and/or the second segregant 722 of the second magnetic recording layer 714 may include C, SiO2, TiOx, AlN, TaN, W, Ti, TiC, TiN, BC, BN, SiN, SiC, TiO2, CrOx, CrN, AlOx, Al2O3, MgO, Ta2O5, B2O3, etc., and combinations thereof. It is important to note that the first segregant 718 may include one or more materials that are the same or different as those comprising the second segregant 722.
According to one particular approach, the first magnetic recording layer 712 may include L10 FePt-C (30-50 at %), and the second magnetic recording layer 714 may include L10 FePt-SiO2 or L10 FePt-TiO2. However, one disadvantage associated with using an oxide segregant in at least one of the magnetic recording layers is that said layer may exhibit columnar shaped magnetic grains, as well as poor overall magnetic properties (e.g., Hc<0.1 Tesla) that may be unsuitable for HAMR purposes.
According to another particular approach, both the first and second magnetic recording layers 712, 714 may include L10 FePt magnetic grains with a carbon segregant therebetween. In this particular approach, the total amount of segregant in each magnetic recording layer 712, 714 may be in a range from about 10 vol % to about 60 vol %.
With continued reference to
Referring again to
Again with reference to
As further shown in
While not shown in
It is important to note, that while incorporation of a carbon segregant in one of the magnetic recording layers of the magnetic recording bilayer structure 702 of
Referring now to
As shown in
The magnetic recording medium 1200 also includes an adhesion layer 1206 positioned above the substrate layer 1204. In various approaches, the adhesion layer 1206 may comprise Ni, Ta, Ti, and/or alloys thereof. In preferred approaches, the adhesion layer may comprise an amorphous material that does not affect the crystal orientation of the layers deposited thereon. In some approaches, the thickness of the adhesion layer may be in a range from between about 5 nm to about 300 nm.
The magnetic recording medium 1200 may additionally include an optional heat-dissipating (heat sink) layer 1208 positioned above the adhesion layer 1206. The heat sink layer 1208, which may include a material having a high thermal conductivity (e.g., greater than 30 W/m-K, preferably greater than 100 W/m-K), may be particularly useful for HAMR purposes. In various approaches, this heat sink layer 1208 may be a plasmonic layer. Suitable materials for the heat sink layer 1208 may include, but are not limited to Ta, Ti, Cr, Fe, Cu, Ag, Pt, Au, Cr, Mo, etc. and alloys thereof. In various approaches, the thickness of the heat sink layer 1208 may in a range between about 10 nm to about 100 nm.
The magnetic recording medium 1200 further includes a seed layer 1210 positioned above the heat sink layer 1208. The seed layer 1210 may act as a texture defining layer, e.g., configured to influence the epitaxial growth of the magnetic recording layers 1214, 1216, 1218 formed thereabove. In some approaches, the seed layer 1210 may include MgO, TiN, MgTiOx, SrTiOx, TiC, etc. or suitable seed layer materials as would become apparent to one skilled in the art upon reading the present disclosure. In more approaches, the seed layer 1210 may have a bilayer structure, e.g., with a lower CrRu layer and an upper Pt layer on the CrRu layer. In particular approaches, the total thickness of the seed layer 1210 may be in a range from about 3 nm to about 10 nm.
The magnetic recording medium 1200 may include an optional onset layer 1212 positioned above the seed layer 1210 and below the magnetic recording multilayer structure 1202, In various approaches, this optional onset layer 1212 may be configured to promote formation of the magnetic recording layers 1214, 1216, 1218 deposited thereabove. In particular approaches, the optional onset layer 1212 may include FePt.
While not shown in
It is important to note that in some approaches, the magnetic recording medium 1200 may include the heat sink layer 1208 and a soft magnetic underlayer, both of which may be positioned between the adhesion layer 1206 and the seed layer 1210. In approaches where both a soft magnetic underlayer and a heat sink layer 1208 are present, the soft magnetic underlayer may be positioned above or below the heat sink layer 1208, as equivalent effects may be provided regardless of the position of the soft magnetic underlayer relative to the heat sink layer 1208.
As also shown in
The magnetic recording layers 1214, 1216, 1218 may be formed using a sputtering process. According to one approach, the magnetic grain material(s) and one or more segregant component(s) may be sputtered from the same target; however, in another approach, the magnetic grain material(s) and/or segregant components) may be sputtered from different, respective targets. The magnetic grain and segregant materials are preferably deposited onto the magnetic recording medium 1200 at the same time, in a heated environment, e.g., from about 400 degrees to about 800° C. in approaches where at least one granular chemically ordered L10 FePt magnetic recording layer is desired.
To facilitate a conformal growth of the first, second and third magnetic recording layers 1214, 1216, 1218, an etching step is preferably (but not necessarily) performed on each of the respective magnetic layers after they are formed. Thus, an etching step may be used to define the upper surface of each of the magnetic layers and expose the material of the magnetic layer, e.g., before an additional layer is formed thereabove. According to various approaches, the etching step may include an Inductively Coupled Plasma (ICP) etch step, etc. or any other etching process that would become apparent to one skilled in the art upon reading the present disclosure.
Accordingly, primarily due to the etching step noted above, the magnetic grains 1228 of the third magnetic recording layer 1218 may be physically characterized by growth directly on the magnetic grains 1224 of the second magnetic recording layer 1216, which may in turn be characterized by growth directly on the magnetic grains 1220 of the first magnetic recording layer 1214. Thus, each of the magnetic grains 1220, 1224, 1228 which are formed directly on top of one another may form a larger magnetic grain 1232 that extends along the total thickness, t, of the magnetic recording multilayer structure 1202.
In some approaches, the total thickness, t, of the magnetic recording multilayer structure 1202 may be between about 3 nm to about 20 nm, preferably from about 10 nm to about 15 nm. In more approaches, each of the three magnetic recording layers 1214, 1216, 1218 may have a respective thickness t1, t2, t3, from about 1 nm to about 10 nm. Moreover, the thicknesses t1, t2, and t3 may be the same or different in various approaches.
In numerous approaches, an average pitch, P, (center-to-center spacing) of the magnetic grains 1220, 1224, 1228 in the first, second and/or third magnetic recording layers 1214, 1216, 1218 may be in a range from about 2 nm to about 11 nm, but could be higher or lower depending on the desired application. Furthermore, an average diameter, d, of the magnetic grains 1220, 1224, 1228 in the first, second and/or third magnetic recording layers 1214, 1216, 1218 may preferably be in a range from about 2 nm to about 10 nm, but could be higher or lower depending on the desired application.
In preferred approaches, the magnetic grains 1232 (e.g., each of which is comprised of a magnetic grain 1228 of the third magnetic recording layer 1218 that is positioned directly above a magnetic grain 1224 of the second magnetic recording layer 1216, which is in turn positioned directly above a magnetic grain 1220 of the first magnetic recording layer 1214) have an average aspect ratio (i.e., total thickness, t, to diameter, d) of about 1.5 or larger.
In some approaches, the magnetic grains 1220 of the first magnetic recording layer 1214, the magnetic grains 1224 of the second magnetic recording layer 1216, and/or the magnetic grains 1228 of the third magnetic recording layer 1218 may include chemically ordered L10 FePt. In more approaches, the magnetic grains 1220 of the first magnetic recording layer 1214, the magnetic grains 1224 of the second magnetic recording layer 1216, and/or the magnetic grains 1228 of the third magnetic recording layer 1218 may include chemically ordered L10 FePtX, where X may include one or more of Ag, Cu, Au, Ni, Mn, Pd, etc. For instance, addition of Ag, preferably in an amount of about 6 at %, may reduce the growth temperature of the layer down to about 870 K. Moreover, addition of Cu, preferably in an amount ranging from about 4 at % to about 8 at %, may reduce the Curie temperature of the layer by about 100 to about 150 K.
In other approaches, the magnetic grains 1220 of the first magnetic recording layer 1214, the magnetic grains 1224 of the second magnetic recording layer 1216, and/or the magnetic grains 1228 of the third magnetic recording layer 1218 may include chemically ordered L10 CoPt. In yet more approaches, the magnetic grains 1220 of the first magnetic recording layer 1214, the magnetic grains 1224 of the second magnetic recording layer 1216, and/or the magnetic grains 1228 of the third magnetic recording layer 1218 may include chemically ordered L10 CoPtX, where X may include Ag, Cu, Au, Ni, Mn, Pd, etc.
In various approaches, the magnetic grains of at least two of the magnetic recording layers may include one or more materials that are the same or different from one another. For instance, in such approaches, the magnetic grains of at least two of the magnetic recording layers may include the same or different molecular structure, molecular composition, and/or relative amount of components. In more approaches, the molecular structure, molecular composition, and/or relative amount of components in the magnetic grains of all three magnetic recording layers 1214,1216, 1218 may be the same or different.
In additional approaches, the first segregant 1222 of the first magnetic recording layer 1214, the second segregant 1226 of the second magnetic recording layer 1216, and/or the third segregant 1230 of the third magnetic recording layer 1218 may include C, SiO2, TiOx, AlN, TaN, W, Ti, TiC, TiN, BC, BN, SiN, SiC, TiO2, CrOx, CrN, AlOx, Al2O3, MgO, Ta2O5, B2O3, etc., and combinations thereof. It is important to note that the molecular structure, molecular composition, and/or relative amount of components in the first segregant 1222, the second segregant 1226 and/or the third segregant 1230 may be the same or different.
In various approaches, the total amount of the first segregant 1222 in the first magnetic recording layer 1214 may be in a range from about 10 vol % to about 60 vol % based on the total volume of the first magnetic recording layer 1214, but may be higher or lower depending on the desired application. Similarly, the total amount of the second segregant 1226 in the second magnetic recording layer 1216 may be in a range from about 10 vol % to about 60 vol % based on the total volume of the second magnetic recording layer 1216, but may be higher or lower depending on the desired application. Additionally, the total amount of the third segregant 1230 in the third magnetic recording layer 1218 may be in a range from about 10 vol % to about 60 vol % based on the total volume of the third magnetic recording layer 1218, but again may be higher or lower depending on the desired application.
In particular approaches, the first segregant 1222 of the first magnetic recording layer 1214 may not primarily include just carbon.
In numerous approaches, the first and third segregants 1222, 1230 of the first and third magnetic recording layers 1214, 1218, respectively, may each be primarily a combination of carbon and a second component, whereas the second segregant 1226 of the second magnetic recording layer 1216 may primarily be carbon. Illustrative materials for the second component of the first and third segregants 1222, 1230 include, but are not limited to, one or more of SiO2, TiOx, AlN, TaN, W, Ti, TiC, TiN, BC, BN, SiN, SiC, TiO2, CrOx, CrN, AlOx, Al2O3, MgO, Ta2O5, B2O3, etc.
As used herein, a segregant that is primarily a combination of carbon and a second component may refer to a segregant in which the combined amount of carbon and the second component is about 95 vol % or greater based on the total volume of the segregant. Moreover, in such approaches where a segregant includes carbon and BN, the relative amount of carbon and BN in the segregant may be: C(x at %)+BN(100−x at %); preferably C(50-80 at %)+BN(20-50 at %).
As also used herein, a segregant that is primarily carbon may refer to a segregant in which the total amount of carbon is about 90 vol % or greater based on the total volume of the segregant.
It should also be noted, however, that in some approaches where the first segregant 1222 of the first magnetic recording layer 1214 includes carbon and a second component, the combined amount of carbon and the second component in the first segregant 1222 may be about 50 vol % or more based on the total volume of the first segregant 1222. Similarly, in some approaches where the third segregant 1230 of the third magnetic recording layer 1218 includes carbon and a second component, the combined amount of carbon and the second component in the third segregant 1230 therein may be about 50 vol % or more based on the total volume of the third segregant 1230. Furthermore, in some approaches where the second segregant 1226 of the second magnetic recording layer 1216 includes carbon, the amount of carbon in the second segregant 1226 may be about 50 vol % or more based on the total volume of the second segregant 1226.
According to one particular approach, the first, second and third magnetic recording layers 1214, 1216, 1218 may each include L10 FePt magnetic grains (and/or L10 FePt-X magnetic grains). However, the first and third segregants 1222, 1230 of the first and third magnetic recording layers 1214, 1218, respectively, may each be primarily a combination of carbon and BN (C+BN), whereas the second segregant 1226 of the second magnetic recording layer 1216 may primarily be carbon. In various approaches the thickness of the FePt-C+BN first magnetic recording layer 1214 may preferably be in a range from about 1 nm to about 3 nm, whereas the thickness of the FePt-C second magnetic recording layer 1216 and the FePt-C+BN third magnetic recording layer 1218 may preferably be in a range from about 1 nm to about 6 nm. This FePt-C+BN/FePt-C/FePt-C+BN magnetic recording trilayer structure may have an overall increased thickness, t, to maximize readback signal, as compared to the single magnetic recording layers with oxide segregants and/or the magnetic recording bilayer structures discussed herein.
As shown in
Referring again to
While not shown in
It is important to note that the magnetic recording medium 1200 of
As shown in in
In preferred approaches, the segregant of 1222 of the first magnetic recording layers 1214 and/or the fourth segregant 1406 of the fourth magnetic recording layer may primarily include boron and/or nitrides (particularly BN) combined with carbon. This may be a preferable arrangement in other approaches regardless of the number of magnetic recording layers. For example, in approaches where at least two magnetic recording layers are present, it may be preferable that the segregant of the lower/bottom magnetic recording layer and/or the segregant of the upper/top magnetic recording layer include boron and/or nitrides combined with carbon.
With continued reference to
It is also important to note that the first, second and third magnetic recording layers in the magnetic recording multilayer structure 1202 may each be of high magnetic anisotropy. Accordingly, in various approaches, the optional fourth magnetic recording layer 1402 (as well as other optional, additional magnetic recording layers) may also preferably each be of high magnetic anisotropy, thus helping to retain the high magnetic anisotropy associated with the magnetic grains extending through the magnetic recording multilayer structure.
It should be noted that the results achieved were accomplished by trial and error, and could not have been predicted without conducting the experimentation resulting in structures such as those shown in
The inventive concepts disclosed herein have been presented by way of example to illustrate the myriad features thereof in a plurality of illustrative scenarios, embodiments, and/or implementations. It should be appreciated that the concepts generally disclosed are to be considered as modular, and may be implemented in any combination, permutation, or synthesis thereof. In addition, any modification, alteration, or equivalent of the presently disclosed features, functions, and concepts that would be appreciated by a person having ordinary skill in the art upon reading the instant descriptions should also be considered within the scope of this disclosure.
It should also be noted that methodology presented herein for at least some of the various embodiments may be implemented, in whole or in part, in computer hardware, software, by hand, using specialty equipment, etc. and combinations thereof.
Moreover, any of the structures and/or steps may be implemented using known materials and/or techniques, as would become apparent to one skilled in the art upon reading the present specification.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of an embodiment of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
