JP2003296912A - Magnetic recording media - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high recording density magnetic recording medium.

[0002]

2. Description of the Related Art Magnetic recording media have been continuously improved in recording density by improving magnetic materials and fine processing techniques. That is, the magnetic material has been improved from the oxide magnetic thin film to the metal magnetic thin film, and the fine processing technique has been made finer by adopting the LSI technique in the semiconductor field.

However, as a result of the rapid improvement in recording density over the speed of high integration of LSIs, the microfabrication technology for magnetic recording media has become insufficient even with LSIs. Unique microfabrication technology for magnetic recording media is needed.

Under such a background, a magnetic recording medium which has recently received attention is a self-aligned magnetic dot array called a patterned medium. IBM is Fe
Fe _x P by reacting two types of polymers including
A colloid in which a polymer is coated around magnetic particles made of t _1-x is formed, and the colloid is coated on a substrate and heat-treated to form a dot array in which magnetic particles of Fe _x Pt _1-x are arranged at regular intervals. Formed (NIKKEI ELECTRONI
CS 2000.4.10. No. 767). It is expected that if one bit of data is recorded on one Fe _x Pt _1-x magnetic particle of this magnetic dot array, an areal recording density of 20 T bits / (inch) ² or more can be achieved. / Although there are still technical issues with the playback head,
The recording density is 200 times higher than the recording density of 100 Gbit / (inch) ² currently under development in the world.

[0005]

However, in view of the recent increase in recording density, the recording density of 20 T bits / (inch) ² is 2020 if the increase rate of the recording density is 60% per year. Moreover, if the annual rate is 100%, it will be achieved at the commercial level in 2010.

The present invention has been made in view of the above problems, and an object thereof is 20 T bits /
It is to provide a magnetic recording medium having a higher recording density than (inch) ² .

[0007]

In order to achieve this object, the present invention provides a magnetic recording medium, wherein a substrate and an a-axis are formed in a direction perpendicular to the substrate surface. And a magnetic thin film of an oriented layered perovskite-type ferromagnetic oxide, wherein the magnetic thin film of the layered perovskite-type ferromagnetic oxide is magnetically formed by a non-magnetic layer formed periodically in the c-axis direction. The bonds are broken, and in the b-axis direction, the magnetic bonds are broken by the periodically formed non-magnetic regions, and dot array-like ferromagnetic regions are periodically formed in the magnetic thin film. It is characterized by

The invention described in claim 2 is the same as claim 1.
In the magnetic recording medium described in the paragraph 1, the periodically formed non-magnetic layer is composed of RE and at least one rare earth element,
AE as at least one alkaline earth metal or Pb
Alternatively, Sn and O are oxygen, and chemical formulas (RE, AE)
It is a non-magnetic layer represented by O.

The invention described in claim 3 is the same as claim 1
Alternatively, in the magnetic recording medium according to the second aspect, the periodically formed non-magnetic region is a region in which magnetic coupling between the ferromagnetic regions is broken by a spin cant effect.

The invention according to claim 4 is the same as claim 1
4. In the magnetic recording medium according to any one of 3 to 3, the layered perovskite-type ferromagnetic oxide has a chemical formula of RE is at least one rare earth element and AE is at least one alkaline earth metal or Pb or Sn. (RE, AE) _{n + 1} Mn _n O _{3n + 1} Raddl
It is characterized in that it is an Mn oxide of the esden Popper phase.

The invention described in claim 5 is the same as claim 1.
The magnetic recording medium according to any one of items 1 to 4, wherein the substrate is a single crystal substrate having a rectangular or parallelogrammic unit lattice on the surface of the substrate.

The invention according to claim 6 is the same as claim 5
In the magnetic recording medium according to, the substrate is a single crystal substrate having a lattice mismatch with the magnetic thin film, and the magnetic thin film has a junction lattice area with the magnetic thin film per unit lattice of the substrate. (S1) is formed so as to be smaller (S1 <S2) than the junction lattice area (S2) with the substrate per unit lattice of the magnetic thin film, and the magnetic thin film is compressed in the interface direction with the substrate. It is characterized in that stress is applied.

The invention according to claim 7 is the same as claim 6
In the magnetic recording medium described in (1), the mismatch of the junction area based on the lattice mismatch (Δ = (S2-S1) / S2) is
It is characterized by being 0.2 to 20%.

The invention described in claim 8 is the invention according to claim 5.
8. The magnetic recording medium according to any one of 1 to 7, wherein the substrate is a layered perovskite type oxide single crystal substrate having an ac face as a substrate surface.

The invention described in claim 9 is the same as claim 5
In the magnetic recording medium according to [1], the substrate is Si (1
10) A single crystal substrate.

According to a tenth aspect of the present invention, in the magnetic recording medium according to any one of the first to ninth aspects, the substrate is periodically distributed in the b-axis direction of the magnetic thin film,
And a step substrate having atomic layer level steps linearly extending in the c-axis direction, further comprising an antiferromagnetic layer formed along the step in the interface region between the substrate and the magnetic thin film. The antiferromagnetic layer has a thickness of not more than one molecular layer of the magnetic thin film.

According to a tenth aspect of the present invention, in the magnetic recording medium according to the tenth aspect, the antiferromagnetic layer comprises RE as at least one rare earth element and AE as at least one alkaline earth element. Metal or Pb or S
n, M is Mn or one kind of metal element of Fe or Cr, and is composed of an antiferromagnetic metal oxide having a simple perovskite structure represented by the chemical formula (RE, AE) MO _3. .

According to a twelfth aspect of the present invention, there is provided the magnetic recording medium according to any one of the first to eleventh aspects.
A buffer layer may be further provided between the substrate and the magnetic thin film.

Further, the invention according to claim 13 is the magnetic recording medium according to claim 12, characterized in that the buffer layer is ZnS.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described below with reference to the drawings.

1A and 1B are views for explaining a structural example of a magnetic recording medium of the present invention. FIG. 1A is a plan view of the magnetic recording medium, and FIG. 1B is a sectional view thereof. Is a layered perovskite type ferromagnetic oxide thin film 2 oriented as an a-axis perpendicular to the surface of the substrate 1 formed on a buffer layer (not shown) provided on the substrate 1 as a magnetic thin film.
In this figure, a layered perovskite type ferromagnetic oxide thin film 2
The shaded area corresponds to the ferromagnetic area 2a responsible for magnetic recording, and the remaining area corresponds to the nonmagnetic areas 2b and 2c.

FIG. 2 is a diagram for explaining the state in the vicinity of the ferromagnetic region 2a in detail. The ferromagnetic region 2a is magnetically interacted with other ferromagnetic regions by the nonmagnetic regions 2b and 2c. Is cut off.

As described above, in the magnetic recording medium of the present invention,
The ferromagnetic regions 2a of the layered perovskite-type ferromagnetic oxide thin film 2 oriented in the a-axis are parallel to the b-axis direction and non-magnetic regions 2b that are periodically interposed in the c-axis direction, and parallel to the c-axis direction. The belt-shaped nonmagnetic regions 2c that are periodically interposed in the b-axis direction block the magnetic interaction between the ferromagnetic regions 2a, and dot-shaped ferromagnetic regions are periodically formed. In this magnetic recording medium, the ferromagnetic region 2a is a
It is a perpendicular magnetization recording medium with axial orientation. That is, in the magnetic recording medium of the present invention, the layered perovskite-type ferromagnetic oxide is oriented so that its a-axis is perpendicular to the substrate surface (that is, the c-axis, which is the stacking direction, lies on the substrate surface). By forming a thin film by (a-axis orientation), a strip-shaped ferromagnetic region is formed.

The layered perovskite type ferromagnetic oxide thin film constituting the magnetic recording medium of the present invention is, for example, a Mn oxide generally represented by the chemical formula (RE, AE) _{n + 1} Mn _n O _{3n + 1} . It is possible to use the Raddlesden Popper phase. Where RE in the above chemical formula
Is at least one rare earth element (Y, La, Ce,
Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
r, Tm, Yb, Lu) and AE is at least 1
The type of alkaline earth metal (Mg, Ca, Sr, Ba) or Pb or Sn. In FIG. 2, RE is La.
Shows the crystal structure of Mn oxide and its orientation when AE is Sr.

The Mn oxide of this composition is a ferromagnetic MnO.
_Two layers and a non-magnetic (RE, AE) O layer are alternately laminated in the c-axis direction, and each time this lamination is repeated n times, (RE, A)
E) The O layer has a crystal structure in which one extra layer is inserted in a self-organizing manner. Due to the presence of the non-magnetic (RE, AE) O layer inserted in this one extra layer, the Mn oxide is present. The magnetic region inside is divided. That is, the Mn oxide of this composition has a ferromagnetic MnO ₂ layer and a non-magnetic (RE, AE) O ₂ layer.
Each time the layer and the layer are alternately laminated n times in the c-axis direction, (RE,
AE) It is a layered ferromagnetic material in which a ferromagnetic region and a non-magnetic region are periodically formed by inserting an extra layer by self-organization by an O layer.

As shown in FIG. 2, the layered perovskite-type ferromagnetic oxide thin film, which is the magnetic thin film of the magnetic recording medium of the present invention, periodically divides the ferromagnetic region in the c-axis direction by the non-magnetic ( RE, AE) O layer (corresponding to 2b in FIG. 2), and adjacent ferromagnetic regions are separated from each other only by a distance of about 0.2 nm via this (RE, AE) O layer. Therefore, it is necessary to design the material so that the strength of the magnetic interaction between the ferromagnetic regions adjacent to each other is weaker than that in the individual ferromagnetic regions.

The strength of the exchange interaction, which defines the strength of the magnetic interaction, is determined by appropriately selecting the atomic species coordinated to the (RE, AE) site (A site) and the composition ratio of the RE element and the AE element. It can be adjusted by selecting and adjusting the band width of 3d electrons of the transition metal atom or adjusting the carrier amount. For example, in (RE, AE) _{n + 1} Mn _n O _{3n + 1} , n = 2
Where RE is La, AE is Sr, and the composition ratio of La and Sr is 1.4: 1.6 (that is, La _1.4 Sr _1.6
For Mn ₂ O ₇ ), a suitable exchange interaction magnitude is obtained in the temperature range of 120 to 270K.

A material having a composition of La _1.4 Sr _1.6 Mn ₂ O ₇ is
When it has two ferromagnetic transition temperatures and is gradually cooled from room temperature, spins in the MnO ₂ layer are aligned at 270 K or less (this ferromagnetic transition temperature is referred to as T _ab ). When the temperature is further reduced to about 120 K, the spins in the MnO ₂ layer are realigned (this ferromagnetic transition temperature is defined as T _c ). In the temperature range between these ferromagnetic dislocation temperatures, Mn
The spins are ferromagnetically aligned in the O ₂ layer, but there is no spin order between the MnO ₂ planes, and the MnO ₂ layers can behave as independent magnetization regions. (T.Ki
mura et. al. , Phys. Rev. Let
t. , 81, 5920 (1998)).

Many thin films tend to form a twin structure having regions oriented in directions different by 90 degrees from each other (H. Asano et. Al., Phys. R).
ev. B56, 5395 (1997)), it is essential that the thin film be uniaxially oriented in the plane in forming the thin film of the layered perovskite type ferromagnetic oxide. It is effective to use an interface between the thin film and the substrate, that is, a single crystal substrate whose unit cell on the substrate surface is rectangular or parallelogram.

For example, in the case of a Si (110) substrate, the atomic arrangement on the outermost surface of the substrate is 0.543 nm × 0.38.
A rectangular unit cell of 4 nm is formed, and a periodic Coulomb potential is formed based on this atomic arrangement.

La _1.4 Sr was formed on the Si (110) substrate.
Considering the case of forming a magnetic thin film of _1.6 Mn ₂ O ₇ , the single crystal of the magnetic thin film has a = 0.3860 nm and c = 2.0.
It is a tetragonal crystal with a wavelength of 380 nm and the 4-unit lattice of the Si (110) plane is 2.172 nm × 0.384 nm. The thin film has a b-axis in the Si {1-10} direction and a c-axis in the Si {10
It is formed so as to match the 0} direction. In this case, the substrate has a lattice mismatch of −0.5% in the a-axis direction and + 6.2% in the c-axis direction with respect to the thin film crystal, and the area of the lattice plane to be joined per unit lattice of the substrate. Is only 5.7% larger than that of the thin film, so that an in-plane uniaxially oriented epitaxial thin film can be obtained.

The step height (one step height) formed on the Si (110) substrate surface is 0.384 nm.
Since it is almost equal to the a-axis length (0.3860 nm) of the magnetic thin film material, the anti-phase domain boundary is not formed at the step position, and the generation of crystal defects in the entire thin film is suppressed.

As a single crystal substrate for forming a thin film,
In addition to Si, the closeness of composition with the thin film and the matching of lattice constants
Good layered perovskite type oxides such as Sr₃T
i₂O ₇It is also effective to use a single crystal ac plane.

When a compressive stress is applied in the in-plane direction of the layered perovskite-type ferromagnetic oxide thin film constituting the magnetic recording medium of the present invention, the easy domain of magnetization may be in the vertical direction. . The reason for this is not clear, but the compressive stress stretches the lattice in the vertical direction to increase the interatomic distance, causing anisotropy in the wave function of the electron in the d orbit, which causes the magnetostriction effect and facilitates the magnetization direction to be perpendicular. It is thought to change to. In the magnetic recording medium of the present invention, this magnetostriction effect is generated by utilizing the crystal lattice strain generated in the magnetic thin film due to the lattice mismatch at the interface between the substrate and the magnetic thin film.

In this case, the above-mentioned magnetostriction effect becomes particularly remarkable when the crystal lattice is distorted by 0.2% or more, but if a substrate having too large a lattice mismatch is used, complete lattice relaxation occurs. It is considered that the distortion effect disappears. Therefore, in order to effectively utilize this magnetostrictive effect in the magnetic recording medium of the present invention, it is effective to use a single crystal substrate in which the area of the lattice plane to be joined per unit lattice of the substrate is narrower than that of the thin film, It is particularly effective to grow a magnetic thin film so as to leave strain on the crystal lattice using a single crystal substrate in which the area of the lattice plane to be joined per unit lattice of the substrate is narrower than that of the thin film by 0.2 to 20%. is there. Here, the magnetic characteristics of the layered perovskite type ferromagnetic oxide will be described. For _{La 1.4 Sr 1.6 Mn 2 O 7} , theoretically be expected to have a magnetization of Mn1 atoms per 3.7μ _B, actually measured values near full-moment is obtained value corresponding to the low temperature There is. Mn based on this magnetization value
When the magnetization per unit volume is calculated by paying attention only to the magnetization region of the O ₂ layer, about 600 emu / cm ³ is obtained, and sufficient magnetization can be generated as a magnetic recording medium.

Next, an example of forming a belt-shaped nonmagnetic region (2c in FIG. 1) extending in the c-axis direction will be described. Magnetic interaction in the b-axis direction between the bands of the ferromagnetic regions formed by the ferromagnetic regions (2a in FIG. 1) continuous in the c-axis direction is blocked, and the ferromagnetic regions are magnetized at an appropriate period. As a method of physically separating, for example, as shown in FIG. 1, it is possible to use a crystalline substrate having atomic layer steps on the surface. In this case, a linear atomic step line is made to extend in a direction parallel to the c-axis direction of the magnetic thin film to be formed, and the magnetic thin film is crystal-grown on this substrate in the step flow mode. Magnetic thin film crystal 1
An antiferromagnetic layer having a thickness corresponding to the molecular layer or less is inserted between the substrate and the magnetic thin film.

The antiferromagnetic layer thus inserted is
It affects the magnetism in the surroundings and causes several molecular layers to become spin-cancelled, blocking the magnetic interaction between the bands of the ferromagnetic region, and as a result, the ferromagnetic region also b in the c-axis direction.
A magnetically independent magnetic recording area is also formed in the axial direction. That is, the above-mentioned antiferromagnetic layer intervenes in the b-axis direction and non-magnetic (RE, AE) in the c-axis direction.
Magnetic interaction is blocked by the O layer. In this case, how many molecular layers in the ferromagnetic region the spin is affected by the inserted antiferromagnetic layer depends on the antiferromagnetic material to be inserted.

In the magnetic recording medium of the present invention, since the layered perovskite type ferromagnetic oxide thin film is used for forming the ferromagnetic region, the matching of the composition and the lattice constant with this magnetic thin film is taken into consideration. Then, as a material for forming the antiferromagnetic layer, it is particularly preferable to adopt a perovskite type oxide (for example, a material having antiferromagnetism among simple perovskites generally represented by the chemical formula (RE, AE) MO ₃ ). It is effective, R in the above chemical formula
E is at least one rare earth element (Y, La, C
e, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
o, Er, Tm, Yb, Lu), and AE is at least one alkaline earth metal (Mg, Ca, Sr, B).
a) or Pb or Sn, and M is Mn, F
It is one kind of metal element of e and Cr.

For example, in the case of La _0.6 Sr _0.4 FeO ₃ , the number of molecules in the ferromagnetic region affected by spin by the antiferromagnetic layer is about several molecular layers, although it depends on the volume of the antiferromagnetic layer. Yes (M. Izumi et. Al., Ph
ys. Rev. B60, 1211 (1999)). If a material having a larger anti-exchange interaction is used for the antiferromagnetic layer, the area will be further increased.

As described above, in the magnetic recording medium of the present invention, the magnetic recording comprising the substrate and the magnetic thin film of the layered perovskite type ferromagnetic oxide in which the a-axis is oriented in the direction perpendicular to the substrate surface. The magnetic thin film of the layered perovskite type ferromagnetic oxide, which is a medium, has its magnetic coupling cut in the c-axis direction by a nonmagnetic layer formed periodically.
Further, in the b-axis direction, the magnetic coupling is broken by the non-magnetic regions that are periodically formed, and as a result, dot array-like ferromagnetic regions are periodically formed in the magnetic thin film.

Here, the layered perovskite type ferromagnetic oxide has, for example, a chemical formula (RE, AE) _{n + 1} Mn _n O _{3n + 1.}
The non-magnetic layer, which is a Mn oxide of the Raddlesden Popper phase represented by, is periodically formed in the magnetic thin film. The non-magnetic layer represented by the chemical formula (RE, AE) O is a self-organized non-formed layer. The non-magnetic region, which is a magnetic layer and is formed periodically, is a region in which the magnetic coupling between the ferromagnetic regions is broken by the spin cant effect.

Further, when a single crystal substrate having a lattice mismatch with the magnetic thin film is used as the substrate, the magnetostrictive effect can be advantageously used. The lattice mismatch in this case is such that the junction lattice area (S1) with the magnetic thin film per unit lattice of the substrate is smaller than the junction lattice area (S2) with the substrate per unit lattice of the magnetic thin film (S1 <S2). , Are selected so that a compressive stress is applied to the magnetic thin film in the direction of the interface with the substrate. From the viewpoint of crystal growth, the mismatch of the junction area based on this lattice mismatch (Δ = (S2-S1) / S
2) is particularly preferably 0.2 to 20%.

Further, as the substrate, a step substrate having atomic layer level steps which are periodically distributed in the b-axis direction of the magnetic thin film and linearly extend in the c-axis direction is used.
If an antiferromagnetic layer formed with a thickness of 1 unit layer or less of the magnetic thin film along the step is further provided in the interface region between the substrate and the magnetic thin film, the spin cant effect produced in the magnetic thin film can be obtained. It can be easily expressed.

As described above, the magnetic recording medium of the present invention employs the layered perovskite type ferromagnetic oxide epitaxial orientation film as the magnetic thin film, and the formation of the ferromagnetic region and the nonmagnetic region is accompanied by the crystal growth. Since it is a self-assembly process, it is possible to easily form a minute-sized ferromagnetic region having a periodic spatial distribution without using a special fine processing technique.

The area per bit of this magnetic recording medium is 1 nm × 4 nm, and the recording areal density is 160 T.
It is ² bits / (inch). That is, it is possible to achieve a recording density as high as about 8 times that of a self-aligned magnetic dot array type magnetic recording medium called a patterned medium.

The recording areal density of the magnetic recording medium of the present invention depends on the composition selection of the layered perovskite type ferromagnetic oxide thin film and the design of the belt-shaped nonmagnetic region extending in the c-axis direction. , Can be designed freely.

Examples of the method for producing the magnetic recording medium of the present invention will be described below.

[Embodiment] FIG. 3 is a view for explaining an example of a substrate used for manufacturing the magnetic recording medium of the present invention.
FIG. 3A is a plan view and FIG. 3B is a sectional view. In this embodiment, as the substrate 3, Si (11) having a step line in the (100) direction with an off angle of 5.71 degrees is used.
0) A step substrate was used. In this case, the terrace width L is about 40 nm, which corresponds to about 10 times the typical b-axis length of simple perovskites. As mentioned above, S
Although the lattice matching between the i (110) substrate and the layered perovskite-type ferromagnetic oxide thin film is good, when the oxide magnetic material is directly formed on the Si substrate, the Si substrate and the layered perovskite-type ferromagnetic oxide thin film are formed. S at the interface with
Since iO ₂ is formed, it may be difficult to form a layered perovskite type ferromagnetic oxide thin film having good crystallinity. In order to avoid this inconvenience, a buffer layer is provided in advance on the substrate 3 before the layered perovskite type ferromagnetic oxide thin film is formed.

FIG. 4 is a diagram for explaining the state of the substrate on which the buffer layer is formed. FIG. 4 (a) is a plan view and FIG.
(B) is a sectional view. In this embodiment, substrate 3 substrate 3
A ZnS buffer layer 4 is formed on top.

Since ZnS and Si have similar crystal structures and lattice constants, the crystallinity of ZnS formed is good, and they sufficiently act as an oxygen barrier. That is,
By providing the ZnS buffer layer 4 on the substrate 3 before forming the layered perovskite type ferromagnetic oxide thin film, formation of SiO ₂ at the interface between the Si substrate and the layered perovskite type ferromagnetic oxide thin film is suppressed. Thus, it becomes easy to form a layered perovskite type ferromagnetic oxide thin film having good crystallinity.

The ZnS buffer layer 4 has a PLD (Pulsed) by appropriately controlling the substrate temperature and the sulfur pressure.
Laser Deposition) method 1.2 nm
An epitaxial film was formed to have a film thickness of. When the ZnS buffer layer 4 after the film formation was heat-treated, the surface thereof had a step-and-terrace structure as shown in FIG.

Subsequent to this, an antiferromagnetic layer made of an antiferromagnetic material was formed.

5A and 5B are views for explaining a state in which an antiferromagnetic layer is formed on a ZnS buffer layer. FIG. 5A is a plan view and FIG. 5B is a sectional view. In this example,
La _0.6 Sr _0.4 FeO ₃ is used as the material of the antiferromagnetic layer 5. The antiferromagnetic layer 5 of La _0.6 Sr _0.4 FeO ₃ is
Epitaxial film formation is performed by the PLD method in which the substrate temperature is appropriately controlled, and crystal growth is performed in a step flow mode to produce Z.
Three molecules were grown on the step edge of the nS buffer layer 4. The step-flow type thin film growth can be performed by setting the temperature of the substrate 3 to be relatively high.

La _0.6 Sr _0.4 F formed in this way
On top of the thin film of eO ₃ and the buffer layer 4 of ZnS, La _1.4 S
A magnetic thin film having a composition of r _1.6 Mn ₂ O ₇ (327 phase) was formed.

6A and 6B are views for explaining the state of the substrate after the magnetic thin film is formed. FIG. 6A is a plan view and FIG. 6B is a sectional view. The magnetic thin film 6 is made of La _0.6 Sr _0.4 FeO ₃
The thin film is formed by the PLD method so as to have the composition of.

According to this method, an a-axis oriented thin film can be obtained by adjusting the substrate temperature and the oxygen partial pressure to be introduced, and the crystal growth mode depends on the growth conditions selected. Either a step flow mode or a layer-by-layer mode can be selected. In this example,
The magnetic thin film 6 is formed of five layers of La _0.6 Sr _0.4 FeO ₃ .

The target for forming the thin film of 327 phase is as follows. First, the raw materials La ₂ O ₃ , SrCO ₃ and Mn ₃ O _{4 are used.}
And were mixed in the composition ratio, calcined at 1050 ° C. for 18 hours, pulverized and mixed, and further at 1500 ° C. for 30 minutes.
After main firing for 2 hours (crushing and mixing twice in the middle), it was confirmed by XRD that a 327-phase polycrystal was formed, and then pressed into pellets for further 48 hours for sintering. Of the five layers of the magnetic thin film 6 composed of 327 phases thus obtained, one layer in the interface region between the magnetic thin film 6 and the substrate 3 and one layer in the surface region were exposed to the substrate 3 or the atmosphere. Since they are in contact with each other, the magnetization cannot be effectively exhibited. Further, since it is considered that about 327 phase 3 molecules adjacent to the antiferromagnetic layer 5 are spin-canceted, the magnetic thin film 6 region adjacent to the antiferromagnetic layer adjacent region cannot effectively exhibit magnetization. As a result, among the magnetic thin films 6, FIG.
6b and 6c shown in (a) are regions in which no magnetization occurs, and only 6a functions as a ferromagnetic region.
That is, only the shaded area 2a shown in FIG. 1 exhibits ferromagnetism, and a dot array of ferromagnet is formed.

[0058]

As described above, according to the magnetic recording medium of the present invention, the layered perovskite type ferromagnetic oxide epitaxial orientation film is adopted as the magnetic thin film.
Since the formation of the ferromagnetic and non-magnetic regions is a self-organization process associated with crystal growth, it is easy to form minute-sized ferromagnetic regions with periodic spatial distribution without using special microfabrication technology. can do.

The magnetic recording medium has an area per bit of 1 nm × 4 nm and a recording surface density of 160 T bits / (inch) ² , and is a self-orientation type magnetic dot array type magnet called a patterned medium. A recording density as high as about 8 times that of a recording medium can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the structure of a magnetic recording medium of the present invention, in which (a) is a plan view and (b) is a sectional view.

FIG. 2 is a diagram for explaining in detail a state in the vicinity of a ferromagnetic region of the magnetic recording medium of the present invention.

3A and 3B are views for explaining a substrate used for manufacturing the magnetic recording medium of the present invention, in which FIG. 3A is a plan view and FIG. 3B is a sectional view.

4A and 4B are diagrams for explaining a state of a substrate on which a buffer layer is formed, in which FIG. 4A is a plan view and FIG. 4B is a sectional view.

5A and 5B are views for explaining a state in which an antiferromagnetic layer is formed on a ZnS buffer layer, FIG. 5A is a plan view, and FIG. 5B is a sectional view.

6A and 6B are views for explaining the state of the substrate after forming the magnetic thin film, where FIG. 6A is a plan view and FIG. 6B is a sectional view.

[Explanation of symbols]

1, 3 substrates Magnetic thin film 2a, 6a Ferromagnetic region 2b, 2c, 6b, 6c Non-magnetic region 4 buffer layers 5 Antiferromagnetic layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01F 10/28 H01F 10/28 10/30 10/30 (72) Inventor Masashi Kawasaki Sagamiono, Sagamihara City, Kanagawa 4-chome 2-5 116 (72) Inventor Yoshinori Konishi 2-2-1 Nagasaka, Yokosuka City, Kanagawa Prefecture Fuji Electric Research Institute (72) Inventor Yoshiyuki Yonezawa 2-2-1 Nagasaka, Yokosuka City, Kanagawa Prefecture Fuji Electric Research Institute, Inc. F-Term (Reference) 5D006 BB01 BB07 CA01 CC01 DA03 FA00 5E049 AB10 AC05 BA06 DB02 DB08

Claims (13)

[Claims] 1. A magnetic thin film of a layered perovskite-type ferromagnetic oxide, comprising a substrate and a magnetic thin film of a layered perovskite-type ferromagnetic oxide whose a-axis is oriented in a direction perpendicular to the surface of the substrate. The magnetic coupling is cut in the c-axis direction by the periodically formed non-magnetic layer, and the magnetic coupling is cut in the b-axis direction by the periodically formed non-magnetic regions. A magnetic recording medium characterized in that a dot array-like ferromagnetic region is periodically formed in a thin film. 2. The periodically formed non-magnetic layer is R
E is at least one kind of rare earth element, AE is at least one kind of alkaline earth metal, or Pb or Sn, O
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a non-magnetic layer represented by a chemical formula (RE, AE) O, where oxygen is oxygen. 3. The periodically formed non-magnetic region comprises:
The magnetic recording medium according to claim 1 or 2, wherein the magnetic coupling between the ferromagnetic regions is broken by a spin cant effect. 4. The layered perovskite type ferromagnetic oxide has a chemical formula (RE, AE) _{n + 1 with} RE being at least one rare earth element and AE being at least one alkaline earth metal or Pb or Sn. Mn of the Raddlesden Popper phase represented by Mn _n O _{3n + 1}
The magnetic recording medium according to any one of claims 1 to 3, which is an oxide. 5. The magnetic recording medium according to claim 1, wherein the substrate is a single crystal substrate whose unit lattice shape on the surface of the substrate is a rectangle or a parallelogram. 6. The substrate is a single crystal substrate having a lattice mismatch with the magnetic thin film, and the magnetic thin film has a junction lattice area (S1) with the magnetic thin film per unit lattice of the substrate. Is formed so as to be smaller than the junction lattice area (S2) of the magnetic thin film per unit lattice with the substrate (S1 <S2), and compressive stress is applied to the magnetic thin film in the direction of the interface with the substrate. The magnetic recording medium according to claim 5, wherein the magnetic recording medium is a magnetic recording medium. 7. The magnetic recording according to claim 6, wherein the mismatch (Δ = (S2−S1) / S2) of the junction area based on the lattice mismatch is 0.2 to 20%. Medium. 8. The magnetic recording medium according to claim 5, wherein the substrate is a layered perovskite type oxide single crystal substrate having an ac plane as a substrate surface. 9. The magnetic recording medium according to claim 5, wherein the substrate is a Si (110) single crystal substrate. 10. The substrate is a step substrate having atomic layer level steps which are periodically distributed in the b-axis direction of the magnetic thin film and linearly extend in the c-axis direction. The antiferromagnetic layer formed according to the step is further provided in an interface region with the magnetic thin film, and the thickness of the antiferromagnetic layer is one molecular layer or less of the magnetic thin film. The magnetic recording medium according to any one of 1 to 9. 11. The antiferromagnetic layer comprises RE as at least one rare earth element, AE as at least one alkaline earth metal, or Pb or Sn, and M as Mn or F.
11. The antiferromagnetic metal oxide having a simple perovskite structure represented by the chemical formula (RE, AE) MO ₃ is used as one kind of metal element of e or Cr, and the metal oxide is defined in claim 10. Magnetic recording medium. 12. The buffer layer is further provided between the substrate and the magnetic thin film.
2. The magnetic recording medium according to any one of 1. 13. The magnetic recording medium according to claim 12, wherein the buffer layer is ZnS.