JPS6295734A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having recording tracks in common use as servocontrol tracks by a simple method by alternately providing thin iron oxide films of magnetite and alpha-hematite to a concentrical or spiral shape on a non-magnetic substrate. CONSTITUTION:An Au underlying film 2 is deposited by sputtering or the like to about 0.3mum thickness on the non-magnetic substrate 1 consisting of Si, etc. and while the temp. of the substrate 1 is maintained at 150 deg.C, an alpha-Fe2O3 film 3 having about 0.2mum thickness is first formed by sputtering on the layer 3 by using Fe as a target in a gaseous mixture composed of gaseous Ar and gaseous O2 under 10mTorr. A laser beam adjusted to 15mum width is then irradiated into a strip shape on the above-mentioned film in an H2 atmosphere, then the laser beam is similarly irradiated to execuet heat treatment, by which only the irradiated part is converted to the concentrical thin ferromagnetic Fe3O4 film 3B and the alpha-Fe2O3 film sandwiched by the same is made to co-exist as it is as the film 3A. The same effect is obtd. even if these alternate films are formed in a spiral shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium used in a magnetic storage device such as a magnetic drum device or a magnetic disk device, and a method for manufacturing the same.

[Prior Art] In magnetic recording technology, there is a strong demand for even higher recording densities. Furthermore, in order to achieve a high areal recording density, it is necessary to increase not only the linear recording density but also the track density. For this purpose, great efforts are being made to develop or improve magnetic recording media, magnetic heads, their drive mechanisms, and the like. Among these, magnetic recording media are required to have excellent magnetic properties and chemical or thermal stability. In order to meet the above requirements, magnetic powders made of acicular crystals of oxides such as γ-Fear3°CrO2, Co-coated Fe, 03, or metals such as Fe and Go have been conventionally used as recording media. Generally, so-called coated magnetic recording media are used, in which magnetic recording media are oriented in the in-plane longitudinal direction. γ-Fe2O3 and Go-
Continuous oxide thin films such as γ-Fe2O3 have been developed, and these thin film media exhibit excellent corrosion resistance, stability,
It is currently considered one of the most promising magnetic recording media.

On the other hand, magnetic head positioning (tracking) control (servo), which is essential for maintaining high reliability and high areal recording density in magnetic recording, generally involves seek servo, which moves the magnetic head to a target track at high speed, and magnetic This is done in dual mode with a follow-up servo that holds the head at the target track position. Among these, follow-up servo is realized using other servo-dedicated surfaces and their position error signals.

However, even if the servo-dedicated surface is used for follow-up servo, the difference in thermal expansion that occurs between the servo disk and the data disk cannot be corrected. Methods to compensate for the difference in thermal expansion are also being considered, but an excellent data surface servo method has not yet been developed.

[Problems to be Solved by the Invention] In view of the above-mentioned current situation, the present invention provides a novel magnetic recording medium that has excellent magnetic properties, corrosion resistance, and temperature stability, and also realizes a tracking servo function. The purpose is to provide.

[Means for Solving the Problems] In order to achieve the above object, the magnetic recording medium of the present invention comprises a region made of Fe3O4 having a spinel structure and a region made of α-Fe203 having a birandom structure on a non-magnetic substrate. The ferromagnetic regions are arranged alternately in a concentric or spiral shape, and the ferromagnetic regions serve both as a recording track and a tracking servo track.

Further, the method for manufacturing a magnetic recording medium of the present invention includes forming a thin film of α-Fe203 on a non-magnetic substrate,
The thin film is heat treated with a laser beam concentrically or spirally in a reducing atmosphere to reduce the beam irradiated area and reduce Fe.
It is assumed to be a 3O4 film.

[Function] The present invention focuses on an oxide as a ferromagnetic material with excellent corrosion resistance and wear resistance, and furthermore, as a manufacturing method, a laser beam is used as a starting point from the α-FeL03 state, which is easy to manufacture a thin film. locally in a reducing atmosphere using
- To obtain a magnetic recording medium that serves both as a recording track and a tracking servo track by a simple method, since a ferromagnetic Fe3O4 film is partially formed by heating above the reduction temperature of the Fe203 film to form a magnetic recording track. I can do it.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram illustrating the invention in detail.

Using the RF bipolar sputtering method, a non-magnetic substrate 1 such as Si is pre-coated with Au to a thickness of 0.34 m to form the base layer 2, and then the substrate temperature is 130°C, argon gas pressure is 20 mTorr, and oxygen gas pressure is applied. An α-F+403 film 3 with a thickness of 0.2 hr was formed on the base layer 2 by sputtering an iron target in a mixed atmosphere of 2 OmTorr, and the α-F+403 film 3 thus obtained was The thin film was subjected to in-air laser beam heat treatment in a stripe shape with a width of 15 ILffl in a hydrogen atmosphere using a CO2 laser with an output of 15 mW, so that only the beam irradiated portion was made into a concentric Fe604 ferromagnetic thin film 3B. The crystal grain size of the ferromagnetic region thus obtained was 600, and the coercive force was 3.
000e, the saturation magnetization was 3ElOe+++u/cc, and the squareness ratio was 0.83.

On the other hand, the region 3A of α-Fe4203 light smell that is not irradiated with the laser beam does not change to Fe3O4 and α-F
e, remains as 03. Strictly speaking, α-Fe2O3 is weakly ferromagnetic, but its magnetism can be considered almost paramagnetic. Therefore, the recording medium in which Fe3O4 and α-Fe203 obtained in this way alternately form concentric circles is Fe.
The portion 03 can be used as both a recording track and a tracking servo track.

Tracking detection of the ferromagnetic magnetic recording track obtained in this way is performed by making the width of the magnetic recording track (ferromagnetic region 3B) smaller than the width of the magnetic helad core 11 used, as shown in FIG. This can be achieved by That is, by first recording and initializing a reference signal on each track, the playback output signal of the tracking servo head, which is installed directly in front of or next to the recording/playback head, is maximized both during recording and playback. To perform tracking servo, if the servo head is installed integrally in front of the recording/reproducing head, the own track to be recorded is used; on the other hand, if the servo head is installed integrally next to the recording/reproducing head, , tracking servo is performed using adjacent or other tracks.Furthermore, once recording is completed, the recorded signal itself is used as a tracking servo signal.

The same effect can be obtained even if the laser beam heat treatment is performed so that the ferromagnetic region becomes spiral-shaped.

Here, as the substrate in FIG. 1, Or,
Those with a base of Au or All, or
It is preferable to use these metals as a substrate, and by using the base as a beam reflective layer during laser beam heat treatment, the heat treatment can be performed with high efficiency.

The sputtering method is not limited to the RF bipolar sputtering method, and various sputtering methods can be used, and the film may be formed by a vapor deposition method.

As the target, not only Fe but also its alloy or oxide can be used.

A laser beam with an output of 15 to IOQ m%ll is used, and can be focused on the film surface to a layer diameter of 5 to 25 L.

When laser beam heat treatment is applied to the α-F eELo 3 film, the power density of the laser beam on the film surface, the moving speed of the medium with respect to the beam during heat treatment, the thermal conductivity of the substrate, the composition of the film, the light absorption rate of the film, etc. The temperature of the membrane changes greatly depending on the temperature. Among these conditions, once the film and substrate are determined in particular, it is possible to control the temperature of the film only by the conditions of the power density of the laser beam and the speed of movement of the medium relative to the beam during the heat treatment, and therefore α-Fe2O3 The reduction temperature when a film is subjected to laser beam heat treatment in a reducing atmosphere can be freely set, and as a result, crystallographic and magnetic properties can be easily controlled over a wide range.

Table 1 shows the ferromagnetic region Fe obtained for sample number 1, which is an example described earlier, and sample numbers 2 to 7, which have different manufacturing conditions.
This figure shows the magnetic properties of 3O4 and its manufacturing conditions. In addition,
Until now, weakly ferromagnetic α-Fe2 with corundum structure
The magnetic recording medium composed of O3 and ferromagnetic Fe30a having a spinel structure and its manufacturing method have been basically described. , Ti, C
Even if elements such as u, V, Si, Au, and Ru are contained, the wood quality of the present invention does not change at all. Sample No. 6 in Table 1 contains CO, and sample No. 7 contains Ti-Cu-Co. This is an example in which it is contained. In all of these magnetic recording media, the ferromagnetic region can serve both as a recording track and a tracking servo track.

[Effects of the Invention] As described above, according to the present invention, there is an excellent effect that the recording area itself functions as a tracking servo track, and as a result, a high areal recording density can be ensured. Furthermore, according to the present invention, by using an oxide film as a recording medium, a medium with excellent stability, corrosion resistance, and magnetic properties can be realized, and there is no need to heat the entire substrate to a high temperature during film formation. This has the effect of increasing the degree of freedom of the substrate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram explaining the present invention in detail, and FIG. 2 is a diagram explaining magnetic head tracking. DESCRIPTION OF SYMBOLS 1...Nonmagnetic substrate, 2...Underlayer, 3=.a-Fe, 2O3 film, 3A--.a-Fea03 region, 3B...Fe3O4 region. (A) Figure 1

Claims (1)

[Scope of Claims] 1) A non-magnetic substrate and regions made of Fe_3O_4 (magnetite) and α-Fe_2O_3 (α-hematite) formed on the substrate and alternately forming concentric or spiral shapes. 1. A magnetic recording medium comprising an iron oxide thin film comprising: 2) A thin film of α-Fe_2O_3 is formed on a non-magnetic substrate, and the α-Fe_2O_3 thin film is heat-treated with a laser beam in a concentric or spiral shape in a reducing atmosphere to reduce the beam irradiated area to form an Fe_3O_4 film. A method of manufacturing a magnetic recording medium, characterized in that: