JPH06301904A - High-density recording and reproducing method - Google Patents

Abstract

PURPOSE:To obtain a method for conducting high-density recording and reproducing by using a magnetic recording material in which many ultrafine particle magnetic bodies are regularly arranged one by one as respective recording units. CONSTITUTION:By the use of a recording material in which a recording layer with regularly arranged ultrafine particle magnetic bodies is formed on a non- magnetic substrate, recording is conducted by the magnetization of the ultrafine particle magnetic bodies through a micromagnetic chip being conical in the shape of its tip and an auxiliary magnetic pole. On the other hand, reproduction is conducted by the detection of a magnetic force between said micromagnetic chip and ultrafine particle magnetic bodies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density recording / reproducing method, and more particularly, to a recording / reproducing method using a magnetic recording medium capable of recording / reproducing with or without utilizing laser light, and others. , A high-density recording / reproducing method using an ultrafine particle array thin film applicable to a rewritable holographic memory.

[0002]

2. Description of the Related Art A magnetic film (magnetic thin film) formed on an appropriate substrate (non-magnetic support) is widely used as a recording medium (magnetic recording medium, magneto-optical recording medium). In particular, the magnitude of the magneto-optical effect is greatest when the direction of magnetization is parallel to the direction of travel of light, and the condition of magnetization perpendicular to the plane also satisfies the requirements for perpendicular magnetic recording, so high-density recording is possible. Suitable for Therefore, in the magnetic recording medium, it is desirable to select a material having a magnetization perpendicular to the surface.

From these requirements, as a magnetic material for a magnetic recording medium, (1) a magnetic material (a typical hexagonal close-packed (hcp) structure magnetoplumbite type Ba ferrite) adopted in a perpendicular magnetic recording medium is used. Or use (2) MnBi, MnCuBi, MnGaGe, M
nAlGe, PtCo (above polycrystal); (YBi)
₃ (FeGa) ₅ O ₁₂ (single crystal); GdCo, GdFe,
TbFe, GdTbFe, TbDyFe (above amorphous), etc. are used.

However, depending on the material, the magnetic films of the above (1) and (2) are difficult to form at a low substrate temperature, or the wavelength range of a semiconductor laser (for example, 780 nm, 8 nm).
(For example, 30 nm), it is not possible to obtain a large magneto-optical effect, a high S / N ratio cannot be obtained, and stability is uncertain.

As a result of the development of magnetic materials free from such inconvenient phenomena, a magnetic film in which a partial oxide of Fe, Ni and / or Co is present in the film together with metallic iron, metallic nickel, metallic cobalt, etc. Was proposed. However, this is used exclusively for a perpendicular magnetization film for recording / reproducing using a perpendicular head.

The present inventor has achieved a higher recording density than ever before.
I have been conducting research for reproduction for a long time, but I thought that it could be done by devising the way of taking recording units. One example thereof is "a magnetic film in which ultrafine ferromagnetic metal particles having a particle size of 100Å or less are dispersed in a transparent matrix having a columnar structure and which are magnetically connected in a direction perpendicular to the film surface and exhibit perpendicular magnetic anisotropy. (Japanese Patent Laid-Open No. 4-3
36404). In this magnetic film, although ultrafine magnetic particles are dispersed in the non-magnetic columnar matrix, they are vertically connected. Therefore, although the magnetic film exhibits shape anisotropy and is easily magnetized in the perpendicular direction, it is difficult to control the position of the column to form a desired magnetic recording medium.

In the magnetic film described in the above-mentioned Japanese Patent Laid-Open No. 4-336404, the ultrafine particle magnetic material used therein may be amorphous, crystalline or a mixture.
The crystal grains have random crystal orientations, and the grain size is 50 to 300Å. However, a drawback of this magnetic film proposed by the present inventor is that the magnetic characteristics of each ultrafine particle magnetic material are different. Recording / reproducing to / from these fine particles is performed by a magnetic force microscope (MFM: Magnetic).
Force Microscope), but it is questionable whether the magnetic force is uniform because a very small difference in magnetic force is used. The magnetic force of the ultrafine magnetic particles is determined by the particle size, crystallinity (crystallinity, crystal orientation), particle shape, and the like. Particle size,
Even if the shapes are made as uniform as possible, the reality is that current technology is quite difficult.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high density recording / reproducing method using a magnetic recording material in which a large number of ultrafine magnetic particles are used as recording units and are regularly arranged. .

[0009]

The high-density recording / reproducing method of the present invention uses a recording material in which a recording layer in which ultrafine magnetic particles are regularly arranged is formed on a non-magnetic substrate, and recording is performed in a tip shape. Is performed by magnetizing the ultrafine particle magnetic body with the conical micromagnetic tip and the auxiliary magnetic pole, while reproducing is performed by detecting the magnetic force between the micromagnetic tip and the ultrafine particle magnetic body. And The "ultrafine particle magnetic material" here has a particle size of 1
0 to 300Å, preferably 50 to 100Å, Fe, C
o, Ni or these ferromagnetic metal elements and other elements such as rare earth elements, Cu, Ti, Mn, Cr, V, Si, A
Any ultrafine particles that exhibit magnetism as an alloy with another non-magnetic element such as s or Se or an intermetallic compound may be used.

The present invention will be described in more detail below. The present invention is a magnetic recording / reproducing method in which each of the ultrafine particle magnetic bodies is used as a recording unit, but such a method has not been reported so far. However, even in the case of fine particles, in the case of a magnetic thin film, those having a particle size of about 300 to 1000Å have only been conventionally reported. This is because a particle size of 300 Å or less cannot be obtained by a general thin film forming method. For particles having a particle size of 300 Å or less, particles are collected by evaporating a metal in a vacuum and rapidly cooling it. Therefore, magnetic colloids for magnetic shielding in which the particles are dispersed have already been put to practical use. On the other hand, in the recording material used in the method of the present invention, the ultrafine particle magnetic bodies 3 are regularly arranged on the non-magnetic body 2 or the high magnetic permeability layer 4 (FIGS. 1 and 2). The structure is largely different from the conventional continuous magnetic thin film (FIG. 4).

In the present invention, the ultrafine magnetic particles 3 may be arranged linearly (FIG. 1) such as one row, two rows, ... N rows, or may be circular or semicircular. . The ultrafine particle magnetic body 3 is preferably a crystal, but may be amorphous or quasi-crystal if it is a ferromagnetic body, or may be a magnetic semiconductor. It is desirable that the directions of the crystals are the same, but it may be random. The space between the ultrafine magnetic particles 3 may be about 50Å. As described above, the fine particles 3 are dispersed and arranged in the non-magnetic matrix 2.

In the present invention, it is desirable that the recording layer having the ultrafine magnetic particles 3 is provided on the high magnetic permeability layer 4 serving as an underlayer. Fine particles of Fe, Co, Ni, etc. exhibit ferromagnetism when they have a particle size of 60 Å or less. Thin the same magnetic layer to produce this connecting effect (several hundred Å or less is required)
Create. Now the particles show ferromagnetism by the same principle. For particles larger than this, this high permeability layer (permeability 30
00 or more) is not always necessary, but an abnormal point such as unevenness is necessary in any case, so it is better to provide it. As a result, recording can be performed with a higher sensitivity (with a smaller magnetic field) on particles of 60 Å or more.

The high magnetic permeability layer is 5 Oe or less, preferably 1.
It has a coercive force of 0 to 0.05 Oe, for example permalloy,
It can be formed of a metal magnetic thin film such as sendust or an alloy of CoZr or Nb. Permalloy is Ni: 50-
80%, Fe: 15 to 50%, Mo: 0 to 1%, Cu:
It is an alloy composed of 0 to 15% and Mn: 0 to 5%, and sendust is Al: 4 to 13%, Si: 4 to 13%, Fe7.
It is an alloy composed of 5 to 92%. This high magnetic permeability layer is formed by a PVD method (physical vapor deposition method) such as a vacuum deposition method.
It can be formed from the above magnetic material at a support temperature of about 100 to 300 ° C. The high magnetic permeability layer 4 does not need to have crystallinity, and an amorphous state is sufficient.

In order to form the ultrafine magnetic particles in rows, it is advantageous to use an electroplating method (electroforming method). Preferably, the high-permeability layer is irradiated with an electron beam having a diameter of about 100 Åφ to create abnormal points such as irregularities, and this is subjected to electroforming.

A non-magnetic protective film 5 may be provided on the ultrafine particle magnetic body in this state. In this case, the protective film should be as thin as possible, preferably 100 Å or less, preferably 50-.
About 100Å is suitable. The material of the protective film is SiO ₂ , SiN, AlN, TiO ₂ , amorphous S
i, carbon and the like.

Incidentally, regardless of the presence or absence of the high-permeability layer, if the fine particle magnetic material is continuously formed in the longitudinal direction with respect to the film surface, a magnetic material having a smaller particle size can be used for recording and reproduction. It is possible. This is STM (Scanning Tunneling
MFM (Magneti), a technology developed from Microscope
c Firce Microscope) is used. That is, whether each particle is magnetized or not magnetized corresponds to 1 and 0, and is digitally recorded. The general MFM represents the surface morphology corresponding to the magnitude of the magnetization, but in the present invention, the MFM is
The recording of 10 is performed because the head is magnetized and the particles are magnetized when they are brought close to the particles, and the particles that are not approached are not magnetized.

The ultrafine particle array according to the present invention generally comprises
It is formed on the non-magnetic support directly or through a high magnetic permeability layer.

As the non-magnetic support (substrate) 1, a suitable non-magnetic material such as a plastic film, ceramics, metal or glass is used. As the support plastics here, not only heat-resistant plastics such as polyimide, polyamide and polyethersulfone but also plastics such as polyethylene terephthalate, polyvinyl chloride, cellulose triacetate, polycarbonate and polymethylmethacrylate are used. it can. Further, the shape of the support may be any shape such as a sheet shape, a card shape, a disk shape, a drum shape, and a long tape shape.

In order to carry out recording and reproduction using such a magnetic recording medium, it is only necessary to selectively magnetize the individual ultrafine particle magnetic bodies as described above. That is, the recording is performed by detecting the magnetic force between the micromagnetic chip having a conical tip shape and the ultrafine particle magnetic body. In addition,
This recording / reproducing system is described in detail on pages 35 to 43 of the material for the Japan Society of Applied Magnetics (MSJ72-6, 1991).

Next, the present invention will be described more specifically by showing examples.

Example 1 A 300 Å permalo film was formed on a polyester film (thickness of about 75 μm) under the following conditions using a vacuum vapor deposition apparatus. Evaporation material Ni-Fe alloy Support temperature 150 [deg.] C. Back pressure of vacuum chamber 1 * 10 < ^-6 > torr Evaporation source interval 26 cm The magnetic permeability of the manufactured permalloy film was 4500. Then, in order to provide an abnormal point on this permalloy film, a commercially available scanning electron microscope was modified to form an electron beam irradiation device. Electron gun LaB ₆ filament Probe current 8 × 10 ^-12 A or more Accelerating voltage 0.5 to 3 KV Minimum beam diameter 30 Å In the digital skin mode, about 100 Å beam diameter is about 2
Beam irradiation was performed on a straight line at intervals of 00Å. The surface of the portion irradiated with the beam was greatly roughened. Then, an electroforming bath 6 having the following composition was prepared. Nickel sulfamate 500 g / l Boric acid 35 g / l Nickel bromide 5 g / l 1,3,6-Trisulfonic acid 2 g / l Sodium lauryl sulfate 3 g / l Liquid temperature 50 ° C. As shown in FIG. Place the provided polyester film 7 on the negative electrode, and add 300 μA
The plating was performed under the conditions of cm ⁻² for 1.0 second (300 μC · cm ⁻² ). Next, when the surface of permalloy was observed with a high-resolution SEM, about 130Å Ni fine particles were arranged. Even when observed by STM, similar fine particles of Ni were arranged.

MFM (magneti) which is a modification of STM
c force microscope) was prepared, and the head part was provided with a coil on the side opposite to the Co head as an auxiliary head made of Co (cobalt), and every other fine particle magnetic material was magnetized and recorded. Then, the magnetization of each particle was measured. An output due to a magnetic force was taken out from the magnetized particles, and almost no output (only a noise component) was obtained from the unmagnetized particles, and a digital signal corresponding to 1, 0 could be obtained.

Comparative Example 1 A permalloy film was prepared in the same manner as in Example 1,
A perpendicular magnetization film (continuous magnetic film 8) of Co—Cr alloy having a grain size of about 2000 Å was formed under the following conditions by using the sputtering method.
The magnetic recording medium shown in was prepared. Base pressure 3.5 × 10 ^-7 Torr target Co-Cr alloy (Cr17
Atm%) Input power 200 W Substrate-target distance 50 mm Argon pressure 2 × 10 ^-2 Torr Substrate temperature Room temperature Film production rate 200 Å / min Then, recording and reproducing were performed at an interval of about 200 Å by the MFM apparatus as in Example 1. Compared to Example 1, the reproduction output was about 1.2 times at the time of recording, but the output was twice even at the time of non-recording, and it was almost impossible to identify the reproduction signal.

[0024]

As a result of the present invention, the ferromagnetic metal fine particles are regularly arranged on the non-magnetic support and recorded / reproduced by the micromagnetic chip. Therefore, it is possible to record and reproduce in a very small area of 300 Å or less. Not only is high-density recording and reproduction possible, but because a high-permeability layer is provided as an underlayer, it is possible to record even ultra-fine particles of 60 Å or less and to improve sensitivity.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an outline of a magnetic recording medium used in a method of the present invention.

FIG. 2 is a schematic view of an example of a magnetic recording medium used in the method of the present invention.

FIG. 3 is a diagram for explaining a process of producing a magnetic recording medium used in the method of the present invention.

FIG. 4 is a schematic diagram of a typical conventional magnetic recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Non-magnetic material 3 Ultrafine particle magnetic material 4 High magnetic permeability layer 5 Protective layer 6 Electroforming bath 7 Polyester film provided with a perlomy layer 8 Continuous magnetic film

Claims (3)

[Claims] 1. A recording material in which a recording layer in which ultrafine magnetic particles are regularly arranged is formed on a non-magnetic substrate, and recording is performed by using a micromagnetic tip with a conical tip and an auxiliary magnetic pole. By magnetizing the body,
On the other hand, reproduction is performed by detecting the magnetic force between the micromagnetic chip and the ultrafine particle magnetic body. 2. The high density recording / reproducing method according to claim 1, wherein a high-permeability layer is provided as an underlayer of the recording layer in which the ultrafine magnetic particles are regularly arranged. 3. The high density recording / reproducing method according to claim 1, wherein a nonmagnetic ultrathin film having a thickness of about 100 Å or less is laminated on a recording layer in which the ultrafine magnetic particles are regularly arranged.