JPS5957413A - Manufacture of magnetic recording medium of oxide thin film - Google Patents

Abstract

PURPOSE:To increase rectangular ratio and coercive force and improve magnetic properties, by a method wherein a continuous thin film of ferromagnetic iron oxide with main constituent of Fe3O4 including cobalt is formed on a substrate and then heated to a specified temperature region and cooled in magnetic field. CONSTITUTION:A continuous thin film of ferromagnetic iron oxide with main constituent of Fe3O4 including cobalt or intermediate composition of Fe3O4 and gamma-Fe2O3 is formed on a substrate, and then heated at a temperature region being not less than 80 deg.C and not more than 350 deg.C and cooled in magnetic field. For example, Fe3O4 including Co 2.5% is used as a target and sputtering is performed within argon gas into polyimide substrate, thereby a magnetic thin film of iron oxide including cobalt is obtained in thickness of 2,500Angstrom . The thin film is oxidized in the air at a temperature of 0 deg.C-300 deg.C for 1hr, and then cooled gradually in d.c. magnetic field of 1 kOe being in parallel to the film surface from 250 deg.C to room temperature at rate of 20 deg.C/min.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium used for magnetic tapes, magnetic disks, etc.

Improving the recording density in magnetic recording devices is a constant trend in this field, and in order to achieve this, it is essential to make the magnetic recording medium thinner and thinner.

Conventionally, so-called coating media, in which a mixture of iron oxide fine particles and a binder is coated on a substrate, have been widely used. These recording media include magnetic tapes for audio, magnetic tapes for VTRs, magnetic tapes for computers, flexible 6-inch disks, and rigid magnetic disks. In conjunction with this, efforts were made to increase the recording density by increasing the coercive force of the medium.

However, if the coating medium has a thickness of several thousand Å,
It is extremely difficult to achieve uniform recording f1 and lrt characteristics in the following manner. Therefore, CO evaporated tape and 4V plated tape have been proposed as high-density recording media to replace coaching media. [7 However, 2 such metals are likely to come in contact with a hard head such as ferrite, resulting in damage to the r::1 surface, abrasion, and corrosion; The more reliable it is, the more reliable it becomes. .

Therefore, we solved this problem and created an oxide magnetic thin film with excellent abrasion resistance and -1F corrosion resistance.
A cobalt-containing iron oxide magnetic thin film containing e304 as a main component and adding 0) to obtain a high magnetic force is attracting attention.

However, such a cobalt-containing iron oxide magnetic thin film may exhibit large pressure demagnetization depending on the degree of oxidation (cobalt content -1, etc.), and the reproduction output may decrease due to contact with the magnetic head. Stable nine boxes; could not get a magnetic shaver. In addition, depending on the formation of the 6G crystalline material ('+1) or the 114 quality of the substrate, sufficient magnetic properties may not be achieved.

The object of the present invention is to solve the above n[2 drawbacks by heating a cobal-containing iron oxide magnetic thin film and cooling it in a magnetic field.

The present invention provides an intermediate composition of 304 or Fe3O4 and 7-Fe2O3 containing cobalt or Q1
- A process of forming a continuous ferromagnetic iron oxide thin film on a substrate, the main component of which is Fe2O3 or one of these three materials containing another metal element eHI additive, and heating the thin film on the substrate at a temperature of 80°C to 350°C. It is characterized in that it includes a step of heating to the following temperature range and then cooling in a magnetic field.

By performing cooling treatment in this magnetic field, it is possible to reduce the pressure and depressurization to +1 J)).

Also, the squareness ratio S (residual magnetic flux density U [/saturated flux density)
, the coercive force squareness ratio S1, and the coercive force 11-c can be increased, and the magnetic properties of the magnetic recording medium can be improved.

gJ, the effect that the magnetic properties are improved by in-situ cooling treatment is theoretically similar to that in the magnetic field of cobalt ferrite.
This is known as the magnetic flux effect, (example * is Satoshi Chikazumi (author A, Physics of Ferromagnetic Materials - 1, published by Shobabō r'2, 1966).
(i4) Breaking i1i! As an application to recording sand, the cooling treatment in the coating 61 bodies (JJ, ;
There is a method that improves magnetic flux 1 such as f[i L, squareness ratio, and coercive force. (Japanese Patent Publication No. 36-5927, Characteristics 11?f 36-18282) If the cobalt-containing iron oxide fine particles are subjected to cooling treatment in magnetic broth in this way, The medium cooling effect increases the temperature by 1°
It is known that there is a drawback in that the characteristics that have been applied to the treatment are more rapidly relaxed with the passage of time 11φ, and return to the state before the treatment. For this reason, cobalt-containing “expenses”
, m particles are subjected to cold J, 11 treatment in a magnetic field, chemical annealing treatment (Japanese Patent Publication No. 39-17113). It was necessary to carry out some kind of stabilization treatment, such as stabilization by 6 (Japanese Patent Publication No. 52-42363). However, the present inventor has found that when cobalt-containing oxide J is cooled in a magnetic field, the addition and reduction properties and magnetic properties are significantly improved, and even without any stabilization treatment. The present invention was made based on the new discovery that it is extremely stable over a long period of time. The cause of this is still not clear -t+\cobalt content N'?
When iron oxide fine particles are coated on a substrate, individual particles are dispersed in a binder and are isolated Ft, '3, whereas the cobalt-containing iron oxide magnetic thin film of the present invention consists of smaller particles. Since it is a continuous film, and each grain is in contact with the grain boundaries to form a dense structure, we believe that it is stabilized by the interaction between the grains.

In order to obtain the effects of the present invention, it is essential that the iron oxide contains cobalt, as described above, but the cobalt content ranges from about 0.2% by weight. It is effective to use ferrite in the range of up to about 25 inches. In addition to the above cobalt, Mn% is added as an additive.
Zn, Co, Ti, etc. are also effective. In addition to flexible substrates such as polyethylene brecrate, polyesterimide, polyimide, and polyamideimide,
There are rigid substrates such as alumite, covered aluminum alloy, and glass.

Next, the present invention will be explained in detail with reference to Examples.

In each example, the magnetic properties were measured at room temperature using a sample vibrating magnetization measuring device. Also, the pressurized demagnetization needle mentioned here is
After magnetizing the sample in an external magnetic field of 3 KOe, the magnetic field was removed, and a pressure of 1000 k17/rri was applied to the sample for 10 seconds in the direction perpendicular to the magnetization direction using a hydraulic press. It was confirmed that there was a good correspondence between the demagnetization and the demagnetization results obtained by continuous reproduction many times using a magnetic tape-shaped sample.

Example 1 A target of Fe 304 containing 2.5 inches of Co by weight percent was sputtered onto a polyimide substrate in argon gas at a sputtering power of 1.5 kW and a sputtering pressure of 6.0 Xl (r3
A cobalt-containing iron oxide magnetic thin film with a thickness of 2500 Å was prepared by sputtering at Torr. 20 minutes in the air
Samples were oxidized for 1 hour at temperatures of 0'C, 250'C, and 300°C, and were slowly cooled from 250°C to room temperature at a rate of 20°C/min in a 1 kOe DC magnetic field parallel to the film surface.

Regarding each characteristic of these samples, the values before heat treatment in 6ab + medium are shown in Table 1, and the values immediately after heat treatment in magnetic field are shown in Table 2.
Table 3 shows the values after heat treatment in a magnetic field and storage at 60°C in air for 3 months.

As can be seen by comparing Tables 1 and 2, improvements in lI? properties can be seen for the samples at any oxidation temperature.

Moreover, as can be seen by comparing Tables 2 and 3, these characteristics remained stable even after being left at 60° C. for 3 months (stable without deterioration).

Table 1 Table 2 Table 3 Example 2 Fe3O4 containing 20% CO in iF#% was targeted, spun on a polyimide substrate in argon gas, spacing power 2.0 kW, snow shaving pressure 7.0 x 10
A cobalt-containing iron oxide magnetic thin film with a thickness of 2100 mm was obtained by sputtering at -3 Torr. The same thin IJ and those oxidized in air at the temperatures shown in Table 4 for 1.5 hours were used as sample '1'. Magnetism after oxidation 1
The electrical resistance in the 1j% table is determined by the distance between the electrodes.1. Ocan 2
The value measured by the 14-child method + J as shown in the 4th F]r,
Ivy.

From this, sample kJ with no C11l conversion, Fe3O
The composition was close to 4°C, and it was treated with R6 at 300°C.
: It can be seen that the material is γ-Fe2O3. Samples tiFe304 and 1-F converted to σ2 at temperatures in between
At an intermediate composition of e2O3. Divide the sample of each oxidation temperature into two, one with its 1″, ′i: each characteristic with 6
;:1 constant, and the other one is J1 for 5"07 minutes from 250"0 to 30℃ in a 1kOe DC magnetic field parallel to the 11g plane! After applying slow cooling using iW, each characteristic was evaluated. The results are summarized in Table 4. IC is +7 in the magnetic field to the untreated test side ((+', 1-. p, written in 410).

(Left below) Table 4 As shown in the results, the samples heat-treated in the tap showed improvements in various magnetic properties in the composition range from F@3 (,14 to 7-Fe2O3) and in the pressurized region. A decrease in eji (about 1/2 to 1/8) is observed.

Example 3. ``Fe3O4 containing 2.5% Co and 3.0% Cu by weight was used as a target, and sputtered on a polyimide substrate in Fulvic/Gas at a sputter power of 2.25 kW, sputtering left 8. A cobalt-containing iron oxide magnetic thin film with a thickness of 4000λ was obtained by sppacking at OX 10-” Torr. This was intoxicated in air at 265°C for 1 hour and used as a sample. Heat treatment in a magnetic field was performed. What wasn't there,
6000e, 8000s, LOKOe, 2
．． Characteristics were measured for a total of 5 types of samples that were slowly cooled from 250°C to 50''C at a rate of 10°C/min in a DC magnetic field parallel to each film surface of 5KOe, and the results are shown in Table 5. Summarized.

The magnetic properties and pressure demagnetization properties of the samples heat-treated in a magnetic field are greatly improved compared to the untreated samples. In this range, the stronger the magnetic field strength, the greater the effect can be obtained.

(Margins below) Table 5 Example 4 In 4tl'% Co 2.0%, Cu 3.
Fe3O4q targetol containing 0% was applied to a polyimide substrate at a spack power of 2.0 IcW in full-bore gas.
, Sunokunoku Pressure 7. (l X I O-3'['o
By sputtering with rr, a thickness of 2,500 mm is formed;
A magnetic thin film containing iron oxide was obtained. This was heated in air at 250°C.
The sample was oxidized for 1 hour at 60 °C to 3
It was slowly cooled from each temperature of 50° C. to room temperature at 10° C./min in a DC magnetic field parallel to the IKOe film surface. Table 6 summarizes the results of measurements of various properties of these samples and untreated samples.

Table 6: In the temperature range from 80°C to 350°C, the samples subjected to cooling treatment in a magnetic field significantly improved both temperament and pressure range (IX characteristics) compared to those without treatment. Only 176
At 0°C, almost no change was observed compared to the untreated sample. Cooling treatment in a magnetic field is effective even when cooled from a high temperature of 350°C or higher, but when the temperature exceeds 350°C, the surface quality of the substrate deteriorates due to heat, so magnetic recording media 2
Example 5 Targeting F'e 304 containing 4.0% Co3.
A cobalt-containing iron oxide magnetic thin film having a thickness of 3J00A was obtained by sputtering at a spack pressure of 8.0×10 Torr.

This was oxidized in air at 265°C for 1 hour.
Cooling from 0° C. as shown in Table 7, slow cooling at 114° C. to 50° C.) Various properties of these samples and untreated samples were measured and summarized in Table 7.

At any cooling rate, both the magnetic properties and pressure demagnetization properties are thicker (improved) compared to the untreated one.200
~b The effect of heat treatment in a magnetic field is remarkable.

(Margins below) Table 7 Example 6 A cobalt-containing I2P magnetic thin film with a thickness of 2500 μm was obtained using the substrate target composition as shown in Table 8 and the batter conditions. This sample was oxidized in air at 250°C for 11 minutes, and a direct current parallel to the membrane surface of 1KOe was applied.

It was slowly cooled from 250°C to room temperature in a magnetic field at a rate of 20°C/min.

Table 9 summarizes the results of 6111 determinations of various properties of these samples and untreated samples. Although the value for the untreated sample is shown within 0, the value is 6 (the effect of heat treatment during t and tit is recognized) even when the difference is 1.

Table 8 □ To and below Margin 9 Table 9 Example 7 F of the composition of Fe90 and Cotfl in intussusception percentage
eCo alloy 1,' elemental partial pressure 60 X I 0-4 Tor
r, 4 & warm box 21] 0°C1 adhesion speed F150/s
Evaporation was carried out under EC conditions, and the surface was treated with fulmite by reaction with oxygen to obtain a 2000 mm thick cobalt-containing V oxide magnetic thin film on an aluminum alloy substrate.

This sample was oxidized at 300° C. for 1 hour in 5c air, and then slowly cooled at 20°/min from 30°C to a chamber vortex in a 20KgallRF+ DC magnetic field parallel to the membrane surface.

Table 10 shows the magnetic properties before and after the heat treatment in the magnetic field.

As described above, improvements in the magnetic properties of cobalt-containing iron oxide magnetic thin films produced by reactive vapor deposition can also be seen by heat treatment in a magnetic field.

Table 10 As explained above, the present invention each contains 1 containing cobalt.
? '@ 304 or an intermediate composition of Fe3O4 and 1-Fe2O3 or γ-Fe 203 or these 3fi
A process of forming a continuous ferromagnetic iron oxide thin film on a substrate, the main component of which is a JIM material containing other gold scrap element additives, - and heating the thin film on the substrate at a temperature of 80°C or more and 350°C or less The process of heating within a range and then cooling in a magnetic field greatly reduces the pressure demagnetization activity, improves the magnetic properties such as squareness ratio S1 coercive force squareness ratio S9, coercive force He, etc. Fe3O4 and γ-
As a method for forming a ferromagnetic iron oxide continuous 87 film mainly composed of an intermediate composition of Fe20B or containing other additives in these three types of materials, V (shown in the Examples) contains cobalt. Fe3O4 mafl: is a method in which Fe3O4 containing other additives is used as a target and is formed by sputtering in a neutral gas or a mixed gas of a neutral gas and an oxidizing gas, in an oxygen atmosphere. In addition to the reactive vapor deposition method, a Fe target is sputtered in an oxidizing atmosphere of A r
Reactive sputtering method (indirect method) in which Fe3Q4 is formed and reduced to obtain a Fe3O4 film, and reactive sputtering method (direct method) in which Fe target is sputtered in an oxidizing atmosphere of Ar+02 to directly form Fe3Q4 on the substrate. However, even in cobalt-containing iron oxide magnetic thin films produced by these methods, the effects of the heating and cooling treatment in a magnetic field as shown in the present invention are the same.

As described below, the present invention has excellent wear resistance and corrosion resistance, and there is no problem of pressure demagnetization related to recording and reproduction characteristics.
A magnetic recording medium with good magnetic properties can be obtained.

−Seki

Claims (1)

[Claims] 1. Fe3O4 or Fe3O each containing cobalt
Intermediate composition between 4 and 1-F'e203 or fil-Fe2
0a, a process of forming a continuous ferromagnetic iron oxide thin film mainly composed of these three types of materials containing other metal element additives on the thread body, and heating the thin film on the substrate at 80°C. An oxide thin +1 characterized by including a step of heating to a temperature range of 350° C. or lower and then cooling in a magnetic field. ,! A method for manufacturing a magnetic recording medium. 2 Fe3O4 containing cobalt or Fe+04 containing other metal element additives is used as Kuguts and sputtered in a neutral gas or a mixed gas of a neutral gas and an oxidizing gas, or further obtained by said sputtering. By oxidizing the obtained thin film, a continuous ferromagnetic iron oxide thin film is formed on the substrate. A method for manufacturing an oxide thin film magnetic recording medium according to claim 1. 3. Evaporate a material consisting of Fe and CO or a mixture of these with other metal element additives from an evaporation source in an oxygen atmosphere, or further evaporate fi' obtained by the evaporation.
1: A method for manufacturing an oxide thin film magnetic recording medium according to claim 1, wherein a continuous ferromagnetic iron oxide thin film is formed on a substrate by oxidizing the film.