Oxide thin film material for ultrahigh-density magnetic recording medium and preparation method and application of oxide thin film material

Abstract

The invention belongs to the technical field of thin film materials, and discloses an oxide thin film material for an ultrahigh-density magnetic recording medium and a preparation method and application of the oxide thin film material. The preparation method comprises the following steps: (1) mixing and grinding raw materials including a perovskite oxide material, an antiferromagnetic oxide material and a ferrous or ferromagnetic oxide material to obtain a particle mixture; (2) pre-sintering the particle mixture obtained in the step (1), grinding, putting into a mold, pressing and shaping, and calcining to obtain a composite target material; and (3) putting a single crystal substrate and the composite target material into a pulse laser deposition system or a radio frequency magnetron sputtering system, and performing deposition at 500-700 DEG C under the oxygen pressure of 5-50 Pa to obtain the oxide thin film material. The oxide film material is high in medium coercive field, high in signal-to-noise ratio, good in thermal stability and large in anisotropy, and the three problems of a recording medium are solved to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thin film materials, and particularly relates to an oxide thin film material for ultra-high density magnetic recording medium, and a preparation method and application thereof. BACKGROUND

[0002] Recording medium is the carrier of information storage, and is closely related to the magnetic recording mode. Throughout the entire development history of hard disk, it can be seen that the recording medium is also constantly evolving, from the early γ-Fe2O3 particle medium to the thin film medium, constantly optimizing the composition and microstructure to obtain better magnetic recording performance to support higher recording density.

[0003] Signal-to-noise ratio, thermal stability and write field have always been the three difficult problems for the further development of magnetic recording medium, and the three difficult problems need to be solved to further improve the recording density. The dynamic characteristic of the coercivity of the medium decreases with the extension of time. The fundamental reason for this dependence of coercivity on time is that the magnetic moment flips over the energy barrier with the assistance of thermal vibration and reverses. In the magnetic recording medium, preventing the magnetic moment from reversing can ensure the stability of the data for a long time, so smaller demagnetizing field and higher coercivity can reduce the energy barrier of the magnetic moment reversal, ensuring data stability.

[0004] Signal-to-noise ratio is closely related to the grain size of the medium, and reducing the grain size of the medium can significantly reduce the reversal noise and improve the signal-to-noise ratio; to obtain high signal-to-noise ratio requires small grain size, while maintaining the thermal stability of the grain, requires the anisotropy of the medium to be improved. Therefore, the write head needs to generate a large enough write field to overcome the magnetic crystal anisotropy field of the medium, and there are two basic methods to obtain a larger write field, one is to select a material with higher magnetic anisotropy, and the other is to geometrically optimize the size of the write head.

[0005] The current high-density magnetic recording technology mainly uses perpendicular magnetic recording (PMR), heat-assisted magnetic recording (HAMR), microwave-assisted magnetic recording (MAMR), patterned recording (BPM), and exchange-coupled magnetic recording technology. However, the magnetic recording media used in the current recording technology all have different drawbacks. In the perpendicular magnetic recording technology, the media mainly uses continuous metal alloy thin films, such as the CoCr perpendicular film developed by Junichi Iwasaki in Japan in 1975 and the CoCr and NiFe double-layer film, which are new types of medium materials that can adapt to perpendicular recording. However, metal alloys as magnetic recording media have high costs and complex preparation processes, and have strict requirements on the production environment. On the other hand, with the increase in storage density, the size of each information bit gradually decreases, and when it reaches a certain level, superparamagnetic effect occurs, leading to the loss of recorded information. In order to break through the density limit, researchers have improved the recording technology, such as heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) technology. Heat-assisted magnetic recording (HAMR) uses laser heating to reduce the coercivity requirement of the magnetic recording medium, which can break through the density limit of PMR. Alloys such as FePt and CoPt can reduce the coercivity when they are temporarily heated by laser, allowing data to be written, and then rapidly cooling to stably save information. Microwave-assisted magnetic recording (MAMR) technology uses the microwave field generated by the spin-torque oscillator (STO) to help flip the magnetic domain, thereby writing smaller magnetic domains without heating the medium, and thus improving the storage density. However, both heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) technology use additional technical means to break through the density limit of magnetic recording, rather than fundamentally breaking through the recording material. Exchange-coupled magnetic recording technology adds a soft magnetic layer to the recording medium layer and uses exchange coupling to reduce the write field while maintaining high thermal stability. However, achieving efficient exchange coupling requires precise control of the thickness and interface quality of two different magnetic materials. This increases the complexity and cost of the recording medium material during the manufacturing process. Patterned recording mainly uses patterned media as a carrier, which is composed of nanoscale island-like single-domain magnetic spot arrays separated by non-magnetic materials. Unlike the above-mentioned continuous thin film recording medium, the size, shape, position, geometric freedom, and recording density of the recording bit are determined during the preparation of the medium. The manufacturing process is complex and expensive, making it difficult to mass-produce.

[0006] The magnetic recording media used in the above recording technologies either have superparamagnetic limitations or have complex processes for reducing the grain size of the medium, resulting in a lack of universality in terms of cost, process complexity, or magnetic performance, and not fundamentally solving the three-difficult problem of recording media.

[0007] Therefore, there is an urgent need for a new preparation method of ultra-high-density magnetic recording medium. SUMMARY

[0008] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes an oxide thin film material for ultra-high density magnetic recording media, its preparation method, and its application. This invention grows an ultra-high density epitaxial magnetic recording medium using pulsed laser deposition or magnetron sputtering methods.

[0009] The first aspect of the present invention provides a method for preparing an oxide thin film material for an ultra-high density magnetic recording medium.

[0010] A method for preparing an oxide thin film material for ultra-high density magnetic recording media includes the following steps:

[0011] (1) Take raw materials perovskite oxide, antiferromagnetic oxide and ferri or ferromagnetic oxide, mix them, grind them to obtain a particulate mixture;

[0012] (2) The particle mixture obtained in step (1) is pre-sintered, then ground, then placed in a mold, pressed and shaped, and then calcined to obtain a composite target material.

[0013] (3) Place the single crystal substrate and the composite target into a pulsed laser deposition system or a radio frequency magnetron sputtering system, and deposit at 500-700°C under an oxygen pressure of 5-50 Pa to obtain an oxide thin film material.

[0014] Preferably, the perovskite oxide material comprises at least one of (Na,Bi)TiO3 (NBT), (K,Na)NbO3 (KNN), BiFeO3 (BFO), BaTiO3 (BTO), PbTiO3 (PTO), Pb(Zr,Ti)O3 (PZT), and SrTiO3 (STO).

[0015] Preferably, the antiferromagnetic material comprises a transition metal oxide, wherein the transition element comprises at least one of Fe, Co, and Ni.

[0016] Preferably, the ferriferrous or ferromagnetic oxide material comprises anti-spinel ferrite or spinel ferrite, such as at least one of NiFe2O4, CoFe2O4, ZnFe2O4, Fe3O4, and NiCo2O4.

[0017] Preferably, the single crystal substrate includes a perovskite single crystal substrate (such as SrTiO3 (STO), LaAlO3 (LAO) etc.), a single crystal silicon substrate (including Si, Si / SiO2, metal-buffered Si or Si / SiO2 substrate), an α-Al2O3 substrate, an MgO substrate, and a single crystal substrate doped with the above materials.

[0018] Preferably, in step (1), the perovskite oxide material, antiferromagnetic oxide material, and ferrimagnetic or ferromagnetic oxide are weighed according to a certain volume ratio. The volume ratio of the perovskite oxide material is greater than or equal to 50%, the total volume ratio of the antiferromagnetic oxide material and the ferrimagnetic or ferromagnetic oxide material is less than or equal to 50%, and the volume percentage of the antiferromagnetic oxide material and the ferrimagnetic or ferromagnetic oxide material is greater than or equal to 20%.

[0019] Preferably, in step (1), all materials have a purity of 99.9% or higher. These materials can be supplied by Aladdin Scientific Company.

[0020] Preferably, in step (1), in order to further ensure that the element content in the oxide thin film material is appropriate, an additional 10% of volatile elements will be added when preparing the composite target to offset the element loss generated during powder calcination, target sintering and thin film deposition.

[0021] Preferably, in step (2), the target sintering is carried out at 700-900℃ for 3-6 hours.

[0022] Preferably, in step (2), the pressing process involves placing the mold in a jack and pressing it for 5-8 minutes to form a target material with a thickness of 3-5 mm and a diameter of 1-2 inches.

[0023] Preferably, in step (3), the crystal orientation of the single crystal substrate is (001) or (111) for perovskite or MgO substrates, (0001) for Si-based substrates, and (0001) or (1120) for α-Al2O3 substrates.

[0024] Preferably, in step (3), the oxygen pressure is 5-50 Pa to ensure that the oxide material has the correct stoichiometry.

[0025] Preferably, in step (3), the deposition process in the pulsed laser deposition (PLD) system uses a pulsed excimer laser or semiconductor laser with a laser energy of 1-4 J / cm². 2 The repetition frequency is 1-20Hz, and the power density of the radio frequency magnetron sputtering is 10-200W / cm². 2 .

[0026] Preferably, in step (3), the temperature of the single crystal substrate during the deposition process is 500-700℃, and more preferably 500℃.

[0027] Preferably, a method for preparing an oxide thin film material for ultra-high density magnetic recording media includes the following steps:

[0028] (1) Weigh the raw materials, including perovskite oxide material, antiferromagnetic oxide material and (sub)ferromagnetic oxide material, according to a certain volume ratio, mix them, grind them, and obtain particulate matter.

[0029] (2) The particles obtained in step (1) are pre-sintered, then ground, then placed in a mold and pressed to obtain a target material, and then calcined to obtain a multiphase composite target material.

[0030] (3) Place the single crystal substrate and the composite target into a pulsed laser deposition (PLD) system or a radio frequency magnetron sputtering system, and deposit the oxide thin film material under an oxygen pressure of 5-50 Pa and a substrate temperature of 500-700 °C.

[0031] The original perovskite oxide materials include (Na,Bi)TiO3 (NBT), (K,Na)NbO3 (KNN), BiFeO3 (BFO), BaTiO3 (BTO), PbTiO3 (PTO), Pb(Zr,Ti)O3 (PZT), SrTiO3 (STO), etc. The antiferromagnetic materials include transition metal oxides, and the transition elements include one or more of Fe, Co and Ni. The (sub)ferromagnetic materials include (anti)spindle ferrites such as NiFe2O4, CoFe2O4, ZnFe2O4, Fe3O4, NiCo2O4, etc. The single crystal substrates include perovskite single crystal substrates (such as SrTiO3 (STO), LaAlO3 (LAO), etc.), single crystal silicon substrates (including Si, Si / SiO2, metal-buffered Si or Si / SiO2 substrates), α-Al2O3 substrates, MgO substrates, and single crystal substrates doped with the above materials.

[0032] Preferably, in step (1), the perovskite oxide material, antiferromagnetic oxide material and (sub)ferromagnetic oxide are weighed according to a certain volume ratio. The volume ratio of perovskite oxide material is greater than or equal to 50%, the total volume ratio of antiferromagnetic and (sub)ferromagnetic materials is less than or equal to 50%, and the volume ratio of antiferromagnetic and (sub)ferromagnetic materials is greater than or equal to 20%.

[0033] Preferably, in step (1), the mass purity of all materials is 99.9% or higher.

[0034] Preferably, in step (1), in order to further ensure that the content of each component in the final oxide thin film material is appropriate, an additional 10% of volatile elements will be added when preparing the target material to offset the losses generated during powder pre-sintering, target calcination and thin film deposition.

[0035] Preferably, in step (2), the pre-sintering is carried out at 700-900℃ for 3-6 hours.

[0036] Preferably, in step (2), the pressing process involves placing the mold in a jack and pressing it for 5-8 minutes to form a target material with a thickness of 3-5 mm and a diameter of 1-2 inches.

[0037] Preferably, in step (3), the crystal orientation of the single crystal substrate is (001) or (111) for perovskite or MgO substrates, (0001) for Si-based substrates, and (0001) or (1120) for α-Al2O3 substrates.

[0038] Preferably, in step (3), the oxygen pressure is 5-50 Pa to ensure that the oxide material has the correct stoichiometry.

[0039] Preferably, in step (3), the deposition process in the pulsed laser deposition (PLD) system uses a pulsed excimer laser or semiconductor laser with a laser energy of 1-4 J / cm². 2 The repetition frequency is 1-20Hz, and the power density of the radio frequency magnetron sputtering is 10-200W / cm². 2 Preferably, in step (3), the temperature of the single crystal substrate is 500-700°C during the deposition process.

[0040] Preferably, in step (3), during the deposition process, the growth rate of the oxide thin film material on the single crystal substrate is 0.5-2 nm / min, for example, 0.57 nm / min.

[0041] In step (3), the specific deposition process is as follows: the laser beam is focused on the surface of the composite target material, and at a sufficiently high energy density and a short pulse time (pulsed excimer laser or semiconductor laser, laser energy of 1-4 J / cm²), the deposition is carried out. 2 (with a repetition frequency of 1-20Hz), the composite target absorbs laser energy and causes the temperature at the spot to rise rapidly above the evaporation temperature of the composite target, resulting in high temperature and ablation. The composite target vaporizes and evaporates, and atoms, molecules, electrons, ions and molecular clusters escape from the surface of the target. These evaporated substances, in turn, continue to interact with the laser, further increasing their temperature and forming regionalized high-temperature and high-density plasma. The plasma nucleates and grows on the single-crystal substrate to form an oxide thin film.

[0042] A second aspect of the present invention provides an oxide thin film material for ultra-high density magnetic recording media.

[0043] An oxide thin film material for ultra-high density magnetic recording media is prepared by the above-described preparation method.

[0044] Preferably, the oxide thin film material prepared by the preparation method has a "1-3" structure, that is, 1-dimensional mutually isolated nanopillars are embedded in a 3-dimensional continuous thin film matrix, the nanopillars are antiferromagnetic and (sub)ferromagnetic composites, the matrix is ​​perovskite oxide, the in-plane size of the nanopillars is less than or equal to 20 nm, and the center-to-center spacing is less than or equal to 40 nm.

[0045] A third aspect of the present invention provides an application of an oxide thin film material for ultra-high density magnetic recording media.

[0046] The oxide thin film materials prepared by the above method are applied in the field of information storage.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] Firstly, in terms of manufacturing process, the preparation process of this invention is simple and streamlined, meeting the needs of large-scale production. Secondly, in terms of cost, the oxide thin film material is far less expensive than alloy media based on precious metals such as Pt, and it overcomes the problem of easy oxidation and corrosion inherent in alloy media, ensuring stability during long-term operation. Finally, in terms of performance, the ferroelectric and ferromagnetic properties of the composite thin film effectively help control the magnetic properties of the material with the electric field, reducing the write field and solving the problem of writing difficulties. Furthermore, the oxide thin film material itself possesses characteristics such as high coercivity, small cell size and spacing, and high magnetization, which greatly improve the signal-to-noise ratio and thermal stability of magnetic storage media. Therefore, it effectively solves the three major challenges of magnetic recording media.

[0049] Furthermore, the size of the magnetic unit cell in the oxide thin film material has been reduced to around 10 nm, achieving a maximum density of 1.6 TB / in. 2 The areal density (i.e., the spacing between cell centers is approximately 20 nm). Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the process for preparing oxide thin film materials according to the present invention.

[0051] Figure 2 This is a schematic diagram of the oxide thin film material deposited according to the present invention. The diagram on the right is an enlarged schematic diagram of the process of depositing oxide thin film material.

[0052] Figure 3 This is a schematic diagram of the structure of the oxide thin film of the present invention.

[0053] Figure 4 This is an atomic force microscope image of the oxide thin film material in Embodiment 1 of the present invention.

[0054] Figure 5 This is a hysteresis loop diagram of the oxide thin film material in Embodiment 1 of the present invention.

[0055] in, Figure 2 In the diagram, 1 represents the sample stage; 2 represents the plasma plume; 3 represents the single crystal substrate; 4 represents the observation window; 5 represents the rotary motor; 6 represents the target stage; 7 represents the target material; 8 represents the laser incident window; 9 represents the laser beam; and 10 represents the plasma.

[0056] Figure 3 In this context, 1' represents the perovskite oxide matrix; 2' represents the single crystal substrate; 3' represents the (sub)ferromagnetic material; and 4' represents the antiferromagnetic material. Detailed Implementation

[0057] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0058] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0059] Figure 1 This is a schematic diagram of the process for preparing oxide thin film materials according to the present invention.

[0060] Figure 2 This is a schematic diagram of the oxide material deposited according to the present invention, and the diagram on the right is a schematic diagram of the thin film deposition process.

[0061] Figure 3 This is a schematic diagram of the structure of the oxide thin film of the present invention.

[0062] Figure 4 This is an atomic force microscope image of the oxide thin film material of Example 1 of the present invention. The image shows that the size of the nanopillars is 17 nm, and the center-to-center spacing is significantly less than 40 nm, indicating that the thin film possesses ultra-high density integration properties.

[0063] Figure 5 This is a hysteresis loop diagram of the oxide thin film material in Embodiment 1 of the present invention. H C Indicates a stubborn or inflexible field. From Figure 5 It can be seen that the saturation magnetic moment within the unit cell is 2.5 μ B With a coercive field of approximately 16.32 kOe, the magnetic recording medium of this invention demonstrates its significant advantages in signal-to-noise ratio, thermal stability, and write field.

[0064] Example 1

[0065] A method for preparing an oxide thin film material for ultra-high density magnetic recording media includes the following steps:

[0066] Step 1: Grinding high-purity powder: Na0.5 Bi 0.5 TiO3 (NBT), NiO, and NiFe2O4 (NFO) were weighed in a volume ratio of 5:3.75:1.25. The raw materials were then placed in an agate mortar and thoroughly ground and mixed. These raw materials included 0.6675g of sodium carbonate (Na2CO3), 2.9344g of bismuth oxide (Bi2O3), 1.8297g of titanium dioxide (TiO2), 4.4141g of nickel oxide (NiO), and 0.7505g of iron oxide (Fe2O3). The purity of these raw materials was 99.99% (provided by Shanghai Aladdin Biochemical Technology Co., Ltd.), resulting in a high-purity powder.

[0067] The second step is pre-sintering: the uniformly mixed high-purity powder is put into a ceramic cup and pre-sintered at 800℃ for 6 hours;

[0068] The third step is grinding: Take out the powder and put it into a mortar and mix it thoroughly.

[0069] Step 4: Place the material into the mold and press it. Then, place the mold into the jack and press it for 5 minutes to make it into a target material with a thickness of 5mm and a diameter of 1 inch.

[0070] Fifth step: sintering: calcining at 1000℃ for 6 hours to obtain the composite target material;

[0071] The sixth step involves the preparation of vertically aligned NBT-NiO-NFO nanocomposite films: The composite target and a strontium titanate (SrTiO3, STO) single-crystal substrate with a crystal plane orientation of (001) are placed in a pulsed laser deposition (PLD) system using a KrF laser with a wavelength of 248 nm and a laser energy of 1 J / cm². 2 The repetition frequency was 5 Hz. A relatively high oxygen pressure of 30 Pa was used to ensure that the NBT in the nanocomposite material had the correct stoichiometry. The film was grown on an STO(001) substrate at a temperature maintained at 550 °C. The film growth rate was approximately 0.57 nm / min. The specific deposition process was as follows: a laser beam was focused on the target surface, and under sufficiently high energy density and a short pulse time (KrF laser with a wavelength of 248 nm and a laser energy of 1 J / cm²), the laser was applied. 2 (with a repetition frequency of 5Hz), the composite target absorbs laser energy and causes the temperature at the spot to rise rapidly above the evaporation temperature of the composite target, resulting in high temperature and ablation. The composite target vaporizes and evaporates, and atoms, molecules, electrons, ions and molecular clusters escape from the surface of the target. These evaporated substances, in turn, continue to interact with the laser, further increasing their temperature and forming regional high-temperature and high-density plasma plumes. The plasma nucleates and grows on the substrate to form oxide thin film materials.

[0072] In Example 1, the size of the magnetic unit cell in the oxide thin film material was reduced to about 10 nm, achieving a density as high as 1.6 TB / in. 2 The areal density (i.e., the spacing between cell centers is approximately 20 nm).

[0073] Example 2

[0074] A method for preparing and applying an oxide thin film material for ultra-high density magnetic recording media includes the following steps:

[0075] Step 1: Grinding high-purity powder: Na 0.5 Bi 0.5 TiO3 (NBT), NiO, and NiFe2O4 (NFO) were weighed in a volume ratio of 5:3:2. The raw materials were then thoroughly ground and mixed in an agate mortar. These raw materials included 0.6122 g of sodium carbonate (Na2CO3), 2.691 g of bismuth oxide (Bi2O3), 1.6779 g of titanium dioxide (TiO2), 3.4813 g of nickel oxide (NiO), and 1.0875 g of iron oxide (Fe2O3). All of these raw materials had a purity of 99.99% (provided by Aladdin Scientific Corporation), resulting in a high-purity powder. To ensure that the Bi and Na content in the final oxide film was appropriate, an additional 10% by mass of Bi and Na was added during the preparation of the target material to offset the losses during the target sintering process and the film deposition process.

[0076] The second step is pre-sintering: the uniformly mixed high-purity powder is put into a ceramic cup and pre-calcined at 800℃ for 6 hours;

[0077] The third step is grinding: Take out the powder and put it into a mortar and mix it thoroughly until it is evenly ground.

[0078] Step 4: Place the material into the mold and press it. Then, place the mold into the jack and press it for 5 minutes to make it into a target material with a thickness of 5mm and a diameter of 1 inch.

[0079] Fifth step: sintering: calcining at 1000℃ for 6 hours to obtain the composite target material;

[0080] The sixth step involves the preparation of vertically aligned NBT-NiO-NFO nanocomposite films: The composite target and a perovskite strontium titanate (SrTiO3, STO) single-crystal substrate with a crystal plane orientation of (001) are placed in a pulsed laser deposition (PLD) system using a pulsed excimer laser with a laser energy of 1 J / cm². 2The repetition frequency was 5 Hz. A relatively high oxygen pressure of 30 Pa was used to ensure the correct stoichiometry of NBT in the nanocomposite material. The film was grown on an STO(001) substrate at a temperature maintained at 550 °C. The film growth rate was approximately 0.57 nm / min. The specific deposition process was as follows: a laser beam was focused on the target surface, and under sufficiently high energy density and a short pulse time (pulsed excimer laser, laser energy 1 J / cm²), the laser was applied. 2 (with a repetition frequency of 5Hz), the composite target absorbs laser energy and causes the temperature at the spot to rise rapidly above the evaporation temperature of the composite target, resulting in high temperature and ablation. The composite target vaporizes and evaporates, and atoms, molecules, electrons, ions and molecular clusters escape from the surface of the target. These evaporated substances, in turn, continue to interact with the laser, further increasing their temperature and forming regionalized high-temperature and high-density plasma. The plasma nucleates and grows on the substrate to form oxide thin film materials.

[0081] Comparative Example 1

[0082] Compared with Example 1, the difference in Comparative Example 1 is that when the volume ratio of NiO is changed to 0, the volume ratio of NBT:NFO is changed to 5:5. The coercive field of the oxide thin film material prepared thereby is significantly reduced, from 20 kOe to 1.1 kOe, which significantly reduces the stability of the magnetic recording medium.

[0083] The calculation process for the above areal density:

[0084] Magnetic unit size = 10nm × 10nm;

[0085] The spacing between magnetic units is 10 nm (i.e., the distance from edge to edge between adjacent magnetic units);

[0086] 1. Calculate the center-to-center spacing (Pitch) of magnetic units.

[0087] The distance from center to center (Pitch) of a magnetic unit = magnetic unit size + spacing;

[0088] Pitch spacing = 10nm + 10nm = 20nm;

[0089] Therefore, the area occupied by each magnetic unit (including the spacing) is:

[0090] Area per bit = Pitch spacing² = (20nm) 2 =400nm 2 ;

[0091] 2. Calculate the areal density (bits / m²) 2 )

[0092] Areal density (AD) is the number of bits that can be stored per unit area.

[0093]

[0094] 3. Convert to bits / inch² (traditional storage unit)

[0095] Since 1m = 39.37 inches, therefore:

[0096] 1m 2 =(39.37) 2 inch 2 ≈1550 inches 2

[0097] therefore:

[0098]

Claims

1. A method for preparing and applying an oxide thin film material for ultra-high density magnetic recording media, characterized in that, Includes the following steps: (1) Take raw materials perovskite oxide, antiferromagnetic oxide and ferri or ferromagnetic oxide, mix them, grind them to obtain a particulate mixture; (2) The particle mixture obtained in step (1) is pre-sintered, then ground, then placed in a mold, pressed and shaped, and then calcined to obtain a multiphase composite target material. (3) Place the single crystal substrate and the composite target into a pulsed laser deposition system or a radio frequency magnetron sputtering system, and deposit the oxide thin film material under an oxygen pressure of 5-50 Pa and a substrate temperature of 500-700 °C.

2. The preparation method according to claim 1, characterized in that, The perovskite oxide material includes at least one of (Na,Bi)TiO3, (K,Na)NbO3, BiFeO3, BaTiO3, PbTiO3, Pb(Zr,Ti)O3, and SrTiO3; And / or, the antiferromagnetic material comprises a transition metal oxide, wherein the transition element in the transition metal oxide includes at least one of Fe, Co, and Ni; And / or, the ferriferrous or ferromagnetic oxide material comprises spinel ferrite or anti-spinel ferrite; And / or, the single crystal substrate includes a perovskite single crystal substrate, a single crystal silicon substrate, an α-Al2O3 substrate, an MgO substrate, and a single crystal substrate doped with the above materials.

3. The preparation method according to claim 1, characterized in that, In step (1), the perovskite oxide material, antiferromagnetic oxide material, and ferrimagnetic or ferromagnetic oxide are weighed according to a certain volume ratio. The volume ratio of perovskite oxide material is greater than or equal to 50%, the total volume ratio of antiferromagnetic oxide material and ferrimagnetic or ferromagnetic oxide material is less than or equal to 50%, and the volume ratio of antiferromagnetic oxide material and ferrimagnetic or ferromagnetic oxide material is greater than or equal to 20%.

4. The preparation method according to claim 2, characterized in that, In step (1), the purity of all materials is above 99.9%; And / or, in step (2), the pre-sintering is carried out at 700-900℃ for 3-6 hours; And / or, in step (3), the crystal orientation of the single crystal substrate is (001) or (111) for perovskite or MgO substrates, (0001) for Si-based substrates, and (0001) or (1120) for α-Al2O3 substrates.

5. The preparation method according to claim 1, characterized in that, In step (3), the deposition process in the pulsed laser deposition system uses a pulsed excimer laser or a semiconductor laser with a laser energy of 1-4 J / cm². 2 The repetition frequency is 1-20Hz, and the power density of the radio frequency magnetron sputtering is 10-200W / cm². 2 ; And / or, in step (3), during the deposition process, the temperature of the single crystal substrate is 500-700℃; and / or, in step (3), during the deposition process, the growth rate of the oxide thin film material on the single crystal substrate is 0.5-2nm / min.

6. A method for preparing an oxide thin film material for ultra-high density magnetic recording media, characterized in that, Includes the following steps: (1) Weigh the raw materials, including perovskite oxide, antiferromagnetic oxide and ferrimagnetic or ferromagnetic oxide, according to a certain volume ratio, mix and grind them to obtain particulate matter. The volume ratio of perovskite oxide is greater than or equal to 50%, the total volume ratio of antiferromagnetic oxide and ferrimagnetic or ferromagnetic oxide is less than or equal to 50%, and the volume percentage of antiferromagnetic oxide and ferrimagnetic or ferromagnetic oxide is greater than or equal to 20%. (2) The particles obtained in step (1) are pre-sintered, then ground, then placed in a mold and pressed to obtain a target material, and then calcined to obtain a composite target material. (3) Place the single crystal substrate and the composite target into a pulsed laser deposition system or a radio frequency magnetron sputtering system, and deposit them under an oxygen pressure of 5-50 Pa to obtain an oxide thin film material; The perovskite oxide material includes at least one of (Na,Bi)TiO3, (K,Na)NbO3, BiFeO3, BaTiO3, PbTiO3, Pb(Zr,Ti)O3, and SrTiO3; And / or, the antiferromagnetic material comprises a transition metal oxide, wherein the transition element in the transition metal oxide includes at least one of Fe, Co, and Ni; And / or, the ferriferrous or ferromagnetic oxide material comprises anti-spinel ferrite or spinel ferrite; And / or, the single crystal substrate includes a perovskite single crystal substrate, a single crystal silicon substrate, an α-Al2O3 substrate, an MgO substrate, and a single crystal substrate doped with the above materials.

7. The preparation method according to claim 6, characterized in that, In step (1), the volume ratio of perovskite oxide material is greater than or equal to 50%, the total volume ratio of antiferromagnetic oxide material and ferrimagnetic or ferromagnetic oxide material is less than or equal to 50%, and the volume ratio of antiferromagnetic oxide material and ferrimagnetic or ferromagnetic oxide material is greater than or equal to 20%; and / or, in step (3), the crystal orientation of the single crystal substrate is (001) or (111) for perovskite or MgO substrate, (0001) for Si substrate, and (0001) or (1120) for α-Al2O3 substrate; and / or, in step (3), the oxygen pressure is 5-50 Pa.

8. The preparation method according to claim 6, characterized in that, In step (3), the deposition process in the pulsed laser deposition system uses a pulsed excimer laser or a semiconductor laser with a laser energy of 1-4 J / cm². 2 The repetition frequency is 1-20Hz, and the power density of the radio frequency magnetron sputtering is 10-200W / cm². 2 ; and / or, in step (3), during the deposition process, the temperature of the single crystal substrate is 500-700℃; and / or, in step (3), during the deposition process, the growth rate of the oxide thin film material on the single crystal substrate is 0.5-2nm / min.

9. An oxide thin film material for ultra-high density magnetic recording media, characterized in that, The oxide thin film material prepared by the preparation method described in claims 1-8 has a "1-3" structure, that is, 1-dimensional mutually isolated nanopillars are embedded in a 3-dimensional continuous thin film matrix, the nanopillars are antiferromagnetic and (sub)ferromagnetic composites, the matrix is ​​perovskite oxide, the in-plane size of the nanopillars is less than or equal to 20 nm, and the center-to-center spacing is less than or equal to 40 nm.

10. The application of the oxide thin film material prepared by the preparation method according to any one of claims 1-8 in the field of information storage.

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