JP2016051494A - Magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording device whose reliability is enhanced by assisting magnetic flux reversal which is determined by a product of an electric field and magnetic field and decreasing the critical value of the product of the electric field and magnetic field.SOLUTION: The magnetic recording device includes a substrate; a first recording medium layer which is formed on the substrate and mainly contains an antiferromagnetic material and a ferrimagnetic material all having electromagnetic effect, or a combination thereof; a second recording medium layer which is formed on the first recording medium layer, to which magnetic information recorded on the first recording layer is transferred and generates magnetization intensity sufficient for reading, and which mainly contains a ferromagnetic material; an electric field application device for applying an electric field to the recording medium; and a magnetic field application device for applying a magnetic field to the recording medium. In the magnetic recording device, a radio wave of a microwave region is applied to the recording medium in addition to the application of the electric field and the magnetic field.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic recording device.

  Hard disk devices are positioned as the core technology of recording technology even in the age of information explosion. The center is the increase in capacity by miniaturization of recording bits. Although high-density recording has been put to practical use by the technique on the extension line due to a combination of optimum conditions of the magnetic recording medium and magnetic head, it is close to the engineering limit and heat assist that makes the recording magnetic field substantially effective (patented) Literature 1) and microwave assist (Patent Document 2) are being studied for practical use.

  On the other hand, paying attention to magnetic recording technology based on a principle different from conventional signal recording and signal holding, the electromagnetic effect (hereinafter referred to as “ME effect”) disclosed in Non-Patent Document 1 is a cross-correlation between electricity and magnetism. Is expected to be applied to hard disk drives.

Japanese Patent Application Laid-Open No. 2014-56631 JP 2013-229084 A

X. He. et. al. , Nature Materials, 9, 579 (2010).

  In a magnetic recording device such as a hard disk drive, information is recorded by selectively manipulating the magnetization direction of a desired area on a recording medium. A technique for manipulating magnetization is required. In order to utilize the above-described ME effect in magnetic recording, it is necessary to selectively cause the ME effect in a desired region.

  That is, one of the key technologies for applying the ME effect to magnetic recording devices is the superposition of electric and magnetic fields in a minute region. Therefore, as a result of intensive studies by the present inventors, the following has been clarified. That is, a first recording medium layer mainly including an antiferromagnetic material, a ferrimagnetic material, or a combination thereof having an electromagnetic effect, and the first recording medium layer arranged adjacent to the first recording medium layer and recorded on the first recording medium layer Using a laminated film including a second recording medium layer mainly containing a ferromagnetic material, on which magnetic information is transferred and generates magnetization having a strength necessary for reading, as a recording medium, In order to develop the ME effect related to the magnetization reversal of the second recording medium layer necessary for magnetic recording, the electric field magnetic field product (E × H), which is the product of the strength of the electric field (E) and the magnetic field (H), is obtained. Regarding the value, there is a critical value corresponding to the constituent material of the first recording medium. On the other hand, even if an electric field product (E × H) is simply set so as to exceed the critical value, dielectric breakdown occurs in the constituent material of the recording medium depending on the magnitude of the electric field (E).

  Accordingly, the present invention aims to provide a magnetic recording device with improved reliability by assisting the magnetization reversal action determined by the electric field product and lowering the critical value of the electric field product required for magnetic recording. .

  The present invention provides a substrate, a first recording medium layer which is provided on the substrate and has an electromagnetic effect, and which mainly includes an antiferromagnetic material, a ferrimagnetic material, or a combination thereof, and a first recording medium Including a second recording medium layer mainly including a ferromagnetic material provided on the layer and transferring magnetic information recorded on the first recording medium layer to generate magnetization having a strength necessary for reading. A recording medium, an electric field applying device that applies an electric field to the recording medium, and a magnetic field applying device that applies a magnetic field to the recording medium, and a microwave region together with the application of the electric field and the magnetic field to the recording medium Provided is a magnetic recording device to which an electromagnetic wave is applied.

  According to the present invention, the arrangement of antiparallel spins of the antiferromagnetic material or ferrimagnetic material mainly contained in the first recording medium layer is an electromagnetic wave in an applied microwave region (hereinafter simply referred to as “microwave”). May be perturbed by the electromagnetic field. Thereby, in the region where the electric field and the magnetic field are superimposed, the spin arrangement state is changed so that the magnetization of the first recording medium layer is reversed by the ME effect, and accordingly, the second recording medium layer It reverses so that the magnetization is in the same direction. That is, by applying electromagnetic waves in the microwave region, the energy at that time can be reduced. As described above, according to the present invention, the critical value of the electric field product (E × H) required for the ME effect in the first recording medium layer related to the magnetization reversal in the second recording medium layer is set. Can be effectively reduced. As a result, the dielectric breakdown of the first recording medium layer (especially the oxide thin film) can be prevented, and the superposition of the electric field and the magnetic field can be stably generated in the magnetic recording medium. In addition, it is possible to provide a magnetic recording device having higher recording density and durability against repeated recording and reproduction.

  The inventors of the present invention, microwave assist recording that additionally applies a microwave having a frequency of several tens of GHz or more (hereinafter referred to as “microwave assist recording that additionally applies a high-frequency magnetic field”), The difference is inferred as follows. The present invention needs to be implemented in consideration of a plurality of and complicated conditions such as recording medium components and microwave resonance conditions, as in microwave-assisted recording in which a high-frequency magnetic field is additionally applied. In addition, the critical value of the electric field product (E × H) required for the ME effect can be lowered. The reason for this is that, unlike the action of microwave assisted recording, in which a high frequency magnetic field is additionally applied, which assists the magnetization reversal of a high coercive force recording medium by spin precession and microwave resonance, The effect of perturbing the antiparallel spin of the antiferromagnet or the ferrimagnet by the electric field or the magnetic field, or both, is the electric field magnetic field product (E × It is inferred to lower the critical value of H). This effect is not required to optimize the resonance conditions as in microwave-assisted recording in which a high-frequency magnetic field is additionally applied, and even if non-resonant, an antiferromagnetic material or a ferrimagnetic material that exhibits the ME effect. It can be said that the perturbation for anti-parallel spin is effective for magnetic recording. As a result, it can be said that the supply power can be optimized to about one-tenth of the microwave frequency required for microwave-assisted recording, and the practicality is high. Further, even if the constituent material of the recording medium is not a pinhole, if the thin film has a non-uniform and thin portion, an event where insulation cannot be maintained, that is, dielectric breakdown is encountered. Although there is a critical point for dielectric breakdown, as long as the critical point is not exceeded, even if there is a bit error as digital information, it can be suppressed to a correctable level. That is, according to the present invention, it is possible to provide a practical new recording technique with improved reliability by suppressing the dielectric breakdown of the constituent material of the recording medium.

  Here, the electromagnetic wave in the microwave region may have a frequency of 1 to 6 GHz. When the microwave energy that assists the magnetization reversal action determined by the electric field product is within the above range, the dielectric breakdown of the constituent material of the recording medium can be sufficiently suppressed.

  According to the present invention, it is possible to provide a magnetic recording device with improved reliability by assisting the magnetization reversal action determined by the electric field product and lowering the critical value of the electric field product necessary for magnetic recording.

It is a schematic diagram which shows the basic principle of the magnetic recording in the magnetic recording device which concerns on this embodiment. It is a schematic diagram which shows the structure of the recording medium in the magnetic recording device which concerns on this embodiment. It is a figure which shows the reduction effect of the critical value (ExH critical value) of the electric field magnetic field product based on Example 1 of this invention, and relative S / N of the recorded signal. It is a figure which shows the reduction effect of the critical value (ExH critical value) of the electric field magnetic field product based on Example 2 of this invention, and the relative S / N of the recorded signal. It is a figure which shows the relationship between the coercive force of the recording medium which concerns on Examples 3-5 of this invention, and the critical value (ExH critical value) of an electric field magnetic field product. It is a figure which shows the relationship between the coercive force of the recording medium based on Examples 6-8 of this invention, and the critical value (ExH critical value) of an electric field magnetic field product. It is a figure which shows the bit error in the recording track position which concerns on Example 9 of this invention. It is a figure which shows the bit error in the recording track position which concerns on Example 10 of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The following description exemplifies a part of the embodiments of the present invention, and the present invention is not limited to these embodiments. As long as the form has the technical idea of the present invention, the present invention is not limited thereto. It is included in the scope of the invention. Each configuration in each embodiment, a combination thereof, and the like are examples, and the addition, omission, replacement, and other changes of the configuration can be made without departing from the spirit of the present invention.
In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

<Magnetic recording device>
The basic principle of magnetic recording in the magnetic recording device according to this embodiment will be described with reference to FIG. The basic elements constituting the magnetic recording device 200 are the recording medium 1 on which magnetic information is recorded using the ME effect, the magnetic field applying device 2 that applies a magnetic field to the recording medium 1, and the recording medium 1. An electric field applying device 3 for applying an electric field is provided. Recording of magnetic information in the magnetic recording device 200 according to the present embodiment is performed by simultaneously applying a magnetic field and an electric field to the recording medium 1. Here, “applying an electric field and a magnetic field simultaneously” means a portion where the electric field and the magnetic field overlap with the recording medium 1, more precisely, the first recording medium layer 101 included in the recording medium 1. (Hereinafter sometimes referred to as “superimposed region”) means temporarily forming. In this embodiment, “ME recording” is performed by “a recording method in which an electric field and a magnetic field are superimposed on a recording medium, and the magnetization direction of the recording medium is manipulated by reversing either the electric field or the magnetic field. Is defined.

  In order to record magnetic information on the recording medium 1 using the ME effect, the applied magnetic field and electric field are superimposed only in a spatially narrow area, and this superimposed area is further placed at an arbitrary location on the recording medium 1. A moving mechanism is required. For this, the head assembly technology used for hard disks can be basically used.

  Specifically, as shown in FIG. 1, a spatially limited magnetic field 25 radiated from the magnetic field application device 2 and a first electrode 31 and a second electrode from the electric field application device 3 are recorded on the recording medium 1. 32, an overlapping region 45 is formed, in which an electric field applied between the two regions overlaps with the electric field. The recording medium 1 is arranged so as to be able to move the superposition region 45. For example, while moving the recording medium 1, the magnetization information is continuously recorded by appropriately switching the magnetic field and electric field of the superposition region. It is possible to record on one first recording medium layer 101.

  The magnetic recording device 200 according to this embodiment is greatly different from the conventional perpendicular magnetic recording system in that the recording medium 1 is applied in addition to the application of the magnetic field (H) 25 from the magnetic field applying device 2 provided in the recording head 7. In other words, the application of the electric field (E) from the electric field applying device 3 is performed. Further, the present invention is characterized in that the electromagnetic wave 26 in the microwave region is applied in addition to the magnetic field (H) to be applied even in the conventional perpendicular magnetic recording method, and thereby the ME effect is exerted on the first recording medium layer 101. The critical value of the electric field magnetic field product (H × E), which is a product of the magnetic field (H) and the electric field (E), required for the expression can be lowered. As an effect, in particular, dielectric breakdown of the recording medium 1 (particularly the first recording medium layer 101) due to the electric field E can be suppressed.

(recoding media)
The recording medium 1 includes a substrate 40, a first electrode 31, a first recording medium layer 101, and a second recording medium layer 102 in this order. The substrate 40 holds the first electrode 31, the first recording medium layer 101, and the second recording medium layer 102. For the first electrode 31, a metal or alloy having high electrical conductivity can be suitably used, and examples thereof include metals or alloys such as Cu, Al, and Pt.

  The first recording medium layer 101 has an electromagnetic effect (hereinafter referred to as “ME effect”), mainly includes an antiferromagnetic material, a ferrimagnetic material, or a combination thereof, and an electric field and a magnetic field applied from the outside. Has a function of storing magnetic information in response to the superposition of the two. Here, “mainly includes” means that an antiferromagnetic material, a ferrimagnetic material, or a combination thereof is included in such an amount that the first recording medium layer 101 exhibits the ME effect as a layer.

  The second recording medium layer 102 mainly contains a ferromagnetic material, and magnetic information recorded on the first recording medium layer 101 is transferred to generate magnetization having a strength necessary for reading. When the second recording medium layer 102 is magnetically connected to the first recording medium layer 101 via exchange coupling, the magnetic information recorded on the first recording medium layer 101 is transferred to the second recording medium. The second recording medium layer 102 is magnetized with the strength necessary for reading out the magnetic information written to the first recording medium layer 101 to the outside. As a result, information is recorded on the recording medium 1. Here, “mainly includes” means that the ferromagnetic material expresses exchange coupling with the first recording medium layer 101 using the second recording medium layer 102 as a layer, and writes to the first recording medium layer 101. It means that the amount of magnetization that is necessary to read out the stored magnetic information to the outside is included.

  When an electric field and a magnetic field are simultaneously applied to the first recording medium layer 101 having the ME effect from the outside, depending on whether the relationship between the applied electric field and the magnetic field is approximately parallel or approximately antiparallel, One antiferromagnetic state is energetically more stable than the other antiferromagnetic state. That is, the magnetization direction of the first recording medium layer 101 can be actively controlled, and as a result, the magnetization state of the adjacent second recording medium layer 102 can be manipulated through the exchange coupling described above. become able to.

(Recording device)
a. Magnetic Field Application Device The magnetic field application device 2 is usually provided as a part of the recording head 7 and includes a recording magnetic field generation unit 22 designed from the requirements regarding the bit length, and an electromagnetic wave 26 in the microwave region that assists the ME effect. (Hereinafter, it may be simply referred to as “microwave”.) The microwave generator 21 for superimposing may be included. As long as there is no special purpose, the assist magnetic field produced by the microwave may be superimposed on the region where the ME effect should be manifested.

  The frequency of the magnetic field generated from the recording magnetic field generator 22 can be, for example, approximately the same as the frequency of the recording magnetic field used in the conventional perpendicular magnetic recording method, and is, for example, several MHz to 2 GHz.

  The frequency of the microwave supplied from the microwave generation unit 21 can be set to 100 MHz to 10 GHz, preferably 500 MHz to 8 GHz, and more preferably 1 to 6 GHz. The microwave energy that assists the magnetization reversal action determined by the electric field product (E × H) is in the above range, so that the constituent material of the recording medium 1, that is, the first recording medium layer 101 and the second recording medium. The dielectric breakdown of the layer 102 or the like can be sufficiently suppressed.

  In the present embodiment, the microwave generation unit 21 is included in the magnetic field application device 2, but is not necessarily included in the magnetic field application device 2. Aside from the magnetic field application device 2, it may be provided as a micro assist wave generator.

b. Electric field application device The electric field application device 3 includes a second electrode 32 and an electrode holding portion 34. In order to apply an electric field from the electric field applying device 3 to the recording medium 1, an electrode serving as a counter electrode of the electric field applying device 3 is necessary. Therefore, the first electrode 31 and the second electrode 32 are provided between the first electrode 31 and the second electrode 32. The recording medium 1 is arranged such that one recording medium layer 101 and the second recording medium layer 102 are arranged.

  The first electrode 31 and the second electrode 32 are connected to a power source 33. At this time, the first electrode 31 may be merely connected to the power source 33, but it is desirable that the first electrode 31 is simultaneously connected to the ground potential.

  At least one of the magnetic field application device 2 and the electric field application device 3 is provided with a function of moving to an arbitrary place on the surface of the recording medium 1 (the surface on the second recording medium layer 102 side). Further, at least one of the magnetic field application device 2 and the electric field application device 3 has a function of controlling the application direction of the magnetic field or electric field. As long as the ME effect can be used, the magnetic field and the electric field may be applied with a slight inclination with respect to each other. The magnetic field application device 2 and the electric field application device 3 are held so as not to be in physical contact with the surface of the recording medium 1 regardless of whether they are used or not used.

(Playback device)
A reproducing apparatus for using recorded information may be mounted on a normally used magnetic head 7 as long as it has a function of reproducing recorded information, and a technique known so far is used. Different from the magnetic head 7, it may be provided as a reproducing device.

<Magnetic recording operation>
As shown in FIG. 1, the electric field applied between the first electrode 31 and the second electrode 32 by the electric field applying device 3 is caused by the presence of the second recording medium layer 102 having electrical conductivity. An electric field 35 applied to a gap portion sandwiched between the second electrode 32 and the second recording medium layer 102, and a first recording medium layer 101 sandwiched between the first electrode 31 and the second recording medium layer 102. The electric field 36 is divided.

  At this time, the electric field 36 is diffused and applied to a wide range of the first recording medium layer 101, but by combining with the spatially limited applied magnetic field 25, the electric field and the magnetic field are overlapped and applied ( (Hereinafter referred to as “overlapping region”) 45 can be narrowly limited. The first recording medium layer 101 present in the overlapping region 45 is given a predetermined electric field and magnetic field, and the spin alignment direction of the antiferromagnetic material or ferrimagnetic material is determined by the ME effect.

  FIG. 1 shows a state in which only the third spin arrangement direction (cell C) from the left among cells A to G is reversed by application of an electric field and a magnetic field. However, the first recording medium layer 101 mainly includes an antiferromagnetic material, a ferrimagnetic material, or a combination thereof, and the magnetization state is not read out from the outside because the two spin directions cancel each other as a whole. Have difficulty.

  Therefore, a second recording medium layer 102 mainly containing a ferromagnetic material that can be exchange-coupled with the first recording medium layer 101 is disposed adjacent to the first recording medium layer 101, and the first recording medium layer By transferring the spin alignment state in the vicinity of the second recording medium layer 102 in 101 to the second recording medium layer 102, the magnetization state of the second recording medium layer 102 can be read from the outside.

  Specifically, as shown in FIG. 1, all the second recording medium layers 102 in the range of the cells A to G except for the cell C show the upward magnetization direction, but only the cell C has the first The recording medium layer 101 faces downward in accordance with the spin arrangement direction in the vicinity of the second recording medium layer 102.

  Thus, when reproducing magnetic information, it is possible to read the magnetization information recorded on the first recording medium layer 101 by determining the magnetization direction of the second recording medium layer 102.

  As long as exchange coupling between the first recording medium layer 101 and the second recording medium layer 102 is maintained, it is possible to provide another layer therebetween.

  According to the magnetic recording device 200 according to the present embodiment, the direction of recorded magnetization can be controlled by manipulating whether the relationship between the applied electric field and magnetic field is approximately parallel or approximately antiparallel. At this time, magnetization reversal occurs only in the overlapping region.

  Since this phenomenon occurs regardless of the size of the ferromagnetic crystal grains mainly contained in the second recording medium layer 102 and the existence of grain boundaries, the direction of magnetization differs between one part of the crystal grains and the other part. Can also be realized. The size and width of the overlapping region can be freely set as long as the first recording medium layer 101 can record the magnetization change, but it is desirable to make it as fine as possible from the viewpoint of increasing the recording density.

In the recording medium 1, one width of the overlapping region 45 (width in the depth direction in FIG. 1) is the direction of the track width TW of the recording medium 1, and the other width of the overlapping region 45 is the bit length. The direction of BL. The size of the track width TW and the bit length BL is not particularly limited, but from the viewpoint of high-density recording, when the material described later is used as the first recording medium layer 101, the track width TW and the bit length BL are Each of them is preferably 1 nm to 200 nm. Note that the size of the overlapping region 45 can be specified not by the width but by the area, and in the present embodiment, it can be implemented in the range of 1 (nm) ^{2 to} 40000 (nm) ² .

  From the viewpoint of efficiently performing ME recording, the magnetic field application device 2 provided facing the recording medium 1 has a spacing of 1 nm as a spacing between the tip of the magnetic head 7 and the outermost surface on the recording operation side in the recording medium 1. It is desirable to arrange it to be ˜30 nm.

  FIG. 2 is a schematic view showing the recording medium in the magnetic recording device according to the present embodiment from the cross-sectional direction. In addition to the substrate 40, the first electrode 31, the first recording medium layer 101, and the second recording medium layer 102, the recording medium 1 includes a first magnetic flux circuit for writing. A third recording medium layer 103 made of a soft magnetic material may be included on the substrate side of the one recording medium layer 101 and the second recording medium layer 102. The electrode 31 and the third recording medium layer 103 may be laminated in the order of the third recording medium layer 103 and the electrode 31 from the substrate 40 side, or the electrode 31 and the third recording medium layer 103 are laminated in this order. Also good.

(First recording medium layer)
The first recording medium layer 101 has a function of writing and recording magnetic information in response to superposition of an electric field and a magnetic field applied from the outside. Suitable characteristics for the first recording medium layer 101 include a large electrical and magnetic coupling coefficient and the ability to exhibit exchange coupling with sufficient strength over a wide temperature range.

  The above characteristics can be obtained by using a material having an excellent ME effect alone, but a combination of an antiferromagnetic material having an ME effect and another antiferromagnetic material having a higher Neel temperature. It can also be obtained by using a composite material. In this case, the thermal and temporal stability of exchange coupling developed between the first recording medium layer 101 and the second recording medium layer 102 tends to be improved. These composite materials can adjust material structure, layer thickness, magnetic properties (anti-ferromagnetic anisotropic energy, Neel temperature, etc.), etc. to maximize exchange coupling in a given temperature range. . Note that, when distinguished from the arrangement of spins, the two properties approximate each other, so that a ferrimagnetic material having the ME effect can be used instead of the antiferromagnetic material having the ME effect.

The first recording medium layer 101 includes, for example, (a) an oxide antiferromagnetic material having a ME effect such as Cr ₂ O ₃ and BiFeO ₃ , or Ga _1-x Al _x FeO ₃ (0 ≦ x ≦ 1). A thin film material including at least one of oxide ferrimagnetic materials having the ME effect can be obtained. Further, (b) oxide antiferromagnetic material having ME effect such as Cr ₂ O ₃ and BiFeO ₃ , or oxide ferrimagnetic material having ME effect such as Ga _1-x Al _x FeO ₃ (0 ≦ x ≦ 1). A mixed crystal based on at least one kind of body is also possible. (C) At least one of the oxide antiferromagnetic material or oxide ferrimagnetic material having the ME effect of (a) or (b), and the oxide antiferromagnetic material having the ME effect or A laminate or a mixture with an antiferromagnetic material having a higher Neel temperature than that of an oxide ferrimagnetic material may be used.

As the antiferromagnetic material, a known antiferromagnetic material having a high Neel temperature can be appropriately selected and used. Typically, Fe ₂ O ₃ , (1-x) Fe ₂ O ₃ —xRh ₂ O ₃ , (1-x) Fe ₂ O ₃ —xRuO ₂ , (1-x) Fe ₂ O ₃ —xIrO ₂ ( However, x may be an oxide antiferromagnetic material such as 0 <x <1) or a metal antiferromagnetic material such as IrMn or FeMn.

  The first recording medium layer 101 may have a thickness of about 1 nm to 1 μm. It goes without saying that the first recording medium layer 101 must be an insulator in order to appear and control the ME effect in the above-described combination of materials.

(Second recording medium layer)
The second recording medium layer 102 has a function of generating a magnetic field for reading magnetic information written in the first recording medium layer 101. As the ferromagnetic material mainly included in the second recording medium layer 102, a hard magnetic material made of a metal alloy, a laminate, or an ordered alloy having such a function can be appropriately selected and used. For example, CoPt, FePt, and alloys thereof are also preferably used. In particular, a CoCrPt system or a CoCrPtB system can be used. In the CoCrPt system, Co—Cr—Pt (Cr content: 14 to 24 at%, Pt content: 8 to 22 at%, balance Co); in the CoCrPtB system, Co—Cr—Pt—B (Cr content: 10 to 24 at%, Pt content 8-22 at%, B content 0-16 at%, balance Co) are preferred.

  The second recording medium layer 102 may include any soft magnetic material. The soft magnetic material may be amorphous or microcrystalline. The soft magnetic material used for the second recording medium layer 102 preferably has a larger saturation magnetic flux density Bs. As the soft magnetic material, a known material exhibiting soft magnetic characteristics with a small coercive force can be appropriately selected and used. For example, cobalt alloys such as CoTaZr, Co—Fe alloys such as CoFe, CoFeB, CoCrFeB, FeCoN, FeCoTaZr, and CoFeZrNb, NiFe, [Ni—Fe / Sn] n multilayer structures, and Ni— such as FeNiMo, FeNiCr, and FeNiSi. Fe-based alloy, Fe-Co alloy such as FeCo, FeCoV, Cr-Fe-based alloy such as FeCr, FeCrTi, FeCrCu, Ta-Fe-based alloy such as FeTa, FeTaC, FeTaN, FeAlSi, FeAl, FeAlSiCr, FeAlSiTiRu, FeAlO FeAl alloy such as FeMgO, FeMg alloy such as FeMgO, FeZr alloy such as FeZrN, FeC alloy, FeN alloy, FeSi alloy, FeP alloy, FeNb alloy, FeHf alloy, FeBf alloy, Fe The MnZn like, it may be used singly or in combination of two or more. Further, a Co alloy containing 80 at% or more of Co, containing at least one of Zr, Nb, Ta, Cr, Mo and the like and having an amorphous structure can be used.

  The second recording medium layer 102 may be a laminated film of the hard magnetic material and the soft magnetic material, or a gradient composition film. Further, the second recording medium layer 102 may be a recording layer used for a so-called ECC (Exchange Coupled Composite) type perpendicular magnetic recording medium.

  The entire second recording medium layer 102 may have a thickness of about 1 to 10 nm.

  The layer structure constituting the recording medium 1, specifically, the first recording medium layer 101, the second recording medium layer 102, the third recording medium layer 103, and the electrode 31 are formed by sputtering, pulse laser deposition, for example. It can be formed by a method appropriately selected from any physical or chemical deposition process such as a method (PLD), an ion beam deposition method (IBD), or a chemical vapor deposition method (CVD).

(substrate)
As the substrate 40, a metal substrate made of a metal material such as aluminum or an aluminum alloy may be used, or a non-metal substrate made of a non-metal material such as glass, ceramic, silicon, silicon carbide, or carbon may be used. As the glass substrate, there are amorphous glass and crystallized glass. As the amorphous glass, general-purpose soda lime glass, aluminosilicate glass, or the like can be used. As the crystallized glass, lithium-based crystallized glass or the like can be used. As the ceramic substrate, a sintered body mainly composed of general-purpose aluminum oxide, aluminum nitride, silicon nitride, or the like, or a fiber reinforced material thereof can be used. Moreover, you may use what formed the NiP layer or the NiP alloy layer on the surface of the board | substrate using the plating method or the sputtering method.

  Here, the substrate 40 has an average surface roughness Ra of 2 nm or less, preferably 1 nm or less. The surface of the substrate may have a fine waviness (Wa) of 0.3 nm or less, and preferably 0.25 nm or less. These numerical ranges are preferable from the viewpoint of making the recording head fly low. The surface waviness (Wa) is a value measured with a stylus type surface average roughness meter in a measurement range of 100 μm.

The recording medium 1 can further use a surface protective layer and a surface lubricating layer that have been used in conventional recording media. The surface protective layer prevents corrosion of the second recording medium layer 102 and prevents damage to the surface of the recording medium 1 when the recording head 7 comes into contact with the recording medium 1, and a conventionally known material can be used. For example, those containing C (diamond-like carbon: DLC), amorphous Si, SiO ₂ , or ZrO ₂ can be used as appropriate. The thickness of the surface protective layer is preferably 1 to 10 nm from the viewpoint of high recording density because the distance between the recording head 7 and the recording medium 1 can be reduced. The surface lubricating layer can be formed by applying a lubricant such as perfluoropolyether, fluorinated alcohol, and fluorinated carboxylic acid in a thickness of 2 to 5 nm.

  As described above, the magnetic recording device according to the present invention can be suitably used in a form known as a hard disk drive, but the present invention is also used for other types of data recording devices, such as probe recording devices. It should be understood that it can. The present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

(Example)
Hereinafter, the present invention will be described based on specific examples.

A sample simulating the recording medium 1 shown in FIGS. The details will be described below.
The substrate 40 is a 1-inch diameter sapphire substrate, the electrode 31 is Pt, the third recording medium layer 103 is a soft magnetic material layer made of a FeCr-based alloy (Fe content 65%), and the first recording medium The medium layer 101 is an oxide antiferromagnetic layer having a ME effect made of Cr ₂ O ₃ , and the second recording medium layer 102 is a metal ferromagnetic layer made of a CoPt-based alloy.

  First, a 65-nm-thick Pt (electrode 31) and a 180-nm-thick FeCr (third recording medium) are formed on the surface of the stepped C-plane sapphire substrate (average surface roughness 1 nm) by RF sputtering. Layer 103) was formed.

Next, high-frequency plasma of 13.56 MHz is applied to the surface of the third recording medium layer 103 at 600 ° C., 0.3 Pa, in an argon / oxygen atmosphere (Ar: O ₂ flow ratio = 9.0: 0.9). A Cr ₂ O ₃ (001) layer having a thickness of 350 nm was formed by a reactive RF sputtering method using a Cr metal target under the condition of power 120W. This Cr ₂ O ₃ layer was used as the first recording medium layer 101.

  Next, a CoPt alloy (Co content: 75%) layer having a thickness of 5 nm was formed by ion beam deposition (IBD) in an argon atmosphere at room temperature. This CoPt alloy layer was used as the second recording medium layer 102. Further, Ru metal 2 nm and Pt metal 5 nm were formed as a protective layer on the second recording medium layer 102, and this was used as a measurement sample. The electric field application device 3 and the magnetic field application device 2 (magnetic head 7) including the microwave generation unit 21 and the recording magnetic field generation unit 22 were installed on the protective layer with an air gap interposed therebetween.

(Samples 1-3)
The coercive force of the second recording medium layer 102 was adjusted to 5000 Oe (sample 1), 5500 Oe (sample 2), and 6500 Oe (sample 3) by changing the combination of the substrate heating temperature and the sputtering rate conditions. .

(Samples 4-6)
Sample 4 is the same as Samples 1 to 3 except that Ga _0.5 Al _0.5 FeO ₃ (001) is used in place of the Cr ₂ O ₃ (001) layer in the first recording medium layer 101. ~ 6 were made. The method for forming the first recording medium layer 101 is as follows.

The substrate 40 is heated to 600 ° C. by a pulsed laser deposition method (PLD method) at a degree of vacuum of 5 to 7 × 10 ⁻⁷ Pa, and an excimer laser is focused on the Ga _0.5 Al _0.5 FeO ₃ target. A Ga _0.5 Al _0.5 FeO ₃ (110) layer was formed to 350 nm.

Hereinafter, in Examples 1 to 10, the above samples 1 to 6 were used, and the hard disk spin stand was modified to perform recording and reproduction on a 1 inch disk. The effect of microwave assist when recording with a track width of 100 nm and a bit length of 10 nm was confirmed. In Examples 1 to 8, measurement was performed on one track, and in Examples 9 and 10, measurement was performed on three tracks.
(Examples 1 and 2)
<Effect of lowering critical value (E × H critical value) of electric field product and change in relative S / N of recorded signal>
Sample 2 and sample 5 were used to confirm the effect of microwave assist. FIG. 3 shows the result of Example 1 using Sample 2 in which the first recording medium layer 101 is Cr ₂ O ₃ , and FIG. 4 shows that the first recording medium layer 101 is Ga _0.5 Al _0. the results of example 2 using ₅ sample 5 is FeO _3.

  The microwave for assisting (micro assist wave) changes the frequency only by changing the intensity to 3 (dBm), changes in the E × H critical value where the ME effect appears, and changes in the relative S / N of the recorded signal It was confirmed. The frequency of the micro assist wave was changed to 0.5, 1, 2, 5, 7, and 8 (GHz). For each frequency, the average value of E × H critical values and the range of variation when checked 20 times are shown. The illustrated E × H critical value is a relative value to the E × H critical value when there is no microwave assistance.

  The E × H critical value was lower than when there was no microwave assistance. The E × H critical value and the relative S / N of the recorded signal change according to the frequency of the micro assist wave, and at 5 GHz, the E × H critical value is minimum and the relative S / N is maximum. It was.

(Examples 3 to 8)
<Relationship between coercivity of recording medium and critical value of electric field product (E × H critical value)>
5 and 6 show the relationship between the magnitude of the coercive force of the recording medium and the E × H critical value. Samples 1 to 6 correspond to Examples 3 to 8, respectively. The micro assist wave has an intensity of 3 (dBm) and a frequency of 5 GHz, and an E × H critical value at which the ME effect appears is measured. FIG. 5 shows the results of Examples 3 to 5 using Samples 1 to ₃ in which the first recording medium layer 101 is Cr ₂ O ₃ , and FIG. 6 shows that the first recording medium layer 101 has Ga _0. the results of examples 6-8 with ₅ Al samples 4-6 is _0.5 FeO _3. 5 and 6, the average value of the E × H critical value and the range of variation when checked 20 times are shown for one example.

  When the coercive force of the second recording medium layer 102 is 5000 Oe (Examples 3 and 6), 5500 Oe (Examples 4 and 7), or 6500 Oe (Examples 5 and 8), the E × H critical value It can be seen that is a substantially constant value, which is lower than when there is no microwave assistance.

(Examples 9 and 10)
<Bit error at recording track position>
Sample 2 and sample 5 were used to confirm the effect of microwave assist. FIG. 7 and FIG. 8 show the signal error generation magnification when recording / reproduction is repeated 50 times for each track. Each track position is determined by a radial distance from the center of the disk. A is 5 mm, B is 8 mm, and C is 10.5 mm. A ′ is 5.1 mm, B ′ is 8.1 mm, and C ′. Is 10.6 mm. A, B, and C were irradiated with a micro assist wave having an intensity of 3 (dBm) and a frequency of 5 GHz, and A ′, B ′, and C ′ were not irradiated with a micro assist wave. FIG. 7 shows the results of Example 9 using Sample 2 in which the first recording medium layer 101 is Cr ₂ O ₃ , and FIG. 8 shows that the first recording medium layer 101 has Ga _0.5 Al _0. the results of example 10 using ₅ sample 4 is FeO _3. It is clear that the microwave assist improves the reliability of the ME recording technology.

Although the recording medium is manufactured in a cleaner environment as the recording density increases, it is not uniform in the first recording medium layer 101 (for example, Cr ₂ O ₃ , BiFeO ₃ ) even without pinholes. When there is a thin part, an event is encountered where insulation cannot be maintained. Dielectric breakdown has a critical point, but as long as the critical point is not exceeded, even if there is a bit error as digital information, it can be suppressed to a correctable level, and it is possible to provide a practical new recording technology Is understood.

  While the present invention has been described based on the embodiments, various modifications can be made to the examples described so far without departing from the scope of the invention described in the claims.

DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2 ... Magnetic field application apparatus, 3 ... Electric field application apparatus, 7 ... Recording head, 21 ... Microwave generation part, 22 ... Recording magnetic field generation part, 25 ... Magnetic field, 26 ... Electromagnetic wave of microwave range, 31 ... 1st electrode, 32 ... 2nd electrode, 33 ... Power supply, 34 ... Electrode holding part, 35, 36 ... Electric field, 45 ... Overlapping area, 40 ... Substrate, 101 ... 1st recording medium layer, 102 ... 1st Second recording medium layer, 103... Third recording medium layer, 200... Magnetic recording device.

Claims (2)

A substrate, a first recording medium layer provided on the substrate and having an electromagnetic effect, mainly including an antiferromagnetic material, a ferrimagnetic material, or a combination thereof; and the first recording medium layer A recording medium comprising a second recording medium layer mainly comprising a ferromagnetic material, wherein the magnetic information recorded on the first recording medium layer is transferred to generate a magnetization having a strength necessary for reading. Medium,
An electric field applying device for applying an electric field to the recording medium;
A magnetic field application device that applies a magnetic field to the recording medium,
A magnetic recording device in which an electromagnetic wave in a microwave region is applied to the recording medium together with the application of the electric field and the magnetic field.   The magnetic recording device according to claim 1, wherein the electromagnetic wave in the microwave region has a frequency of 1 to 6 GHz.

Images