JPS6295735A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having recording tracks in common use as tracking servo tracks by a simple method by alternately providing thin iron oxide films of magnetic and alpha-hematite to a concentration 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-Fe2O4 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 stripe shape on the above-mentioned film in an H2 atmosphere to execute heat treatment, by which only the irradiated part is converted to the concentrical thin ferromagnetic Fe3O4 film 3B. The film in which alpha-Fe2O3 and Fe3O4 coexist is subjected to a heat treatment at 330 deg.C in air to convert the film 3B to a thin ferromagnetic gamma-Fe2O film. The part where there is no beam irradiation is made to remain as the alpha-Fe2O3. The surface recording density is thus improved.

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 5-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, γ-Fs2O3 and CrO2 have been conventionally used as magnetic recording media in order to meet the requirements of 0 or more, which require characteristics such as excellent magnetic properties and chemical or thermal stability.

Co deposition - oxides such as Fe2O3 or Fe and G
A so-called coating-type magnetic recording medium is generally used, in which magnetic powder made of needle-shaped metal crystals such as O is oriented in the in-plane longitudinal direction of the recording medium. In addition, (γ-Fe2O3 made by vacuum evaporation, sputtering, ion blating, etc. for the purpose of improving magnetic recording properties over C)
Continuous thin films of oxides such as and Go-γ-Fe2O3 have been developed, and these thin film media exhibit excellent corrosion resistance and stability, and are currently considered to be 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 γ-Fe2O having a spinel structure on a non-magnetic substrate.
α-Fe2O with a region consisting of 3 and a corundum structure
3 regions are arranged alternately in a concentric or spiral shape, and the ferromagnetic region of these regions serves both as a recording track and a tracking servo track.

In addition, the method for manufacturing a magnetic recording medium of the present invention involves forming a thin film of α-Fe2O3 on a non-magnetic substrate, heat-treating the thin film with a laser beam in a reducing atmosphere in a concentric or spiral manner, and irradiating the thin film with a laser beam. part is reduced to Fe304
By heat-treating a film in which a-Fe103 and Fe30a coexist in air, Fe,0
4 film is y-Fe, 03 film.

[Function] The present invention focuses on oxides as ferromagnetic materials with excellent corrosion resistance and wear resistance, and furthermore, as a manufacturing method, a laser is used as a starting point from the α-Fe2.03 state, which is easy to manufacture thin films. This is a simple method because a ferromagnetic Fe,04 film is partially formed by heating the α-Fe2O3 film locally using a beam to a temperature higher than its reduction temperature in a reducing atmosphere to form a magnetic recording track. A magnetic recording medium that serves both as a recording track and a tracking servo track can be obtained.

[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 brazed with Au to a thickness of 0.3 pLrn to form the underlayer 2, and then the substrate temperature is 150° C. and the argon gas pressure is 10 pLrn. Oxygen gas pressure 10mTorr
By sputtering an iron target in a mixed atmosphere of
O3 pi 3 is formed, and the α-
By performing in-air laser beam heat treatment on the Fe2O3 thin film in the form of stripes with a width of 15 gm in a hydrogen atmosphere using a CO2 laser with an output of 15 mW, only the beam irradiated area is formed into concentric Fe? 04 ferromagnetic thin film 3B. Further, the film in which α-Fe, 03, and Fe3O4 coexisted was heat-treated in air at 330° C. to form a concentric strong ms 3 B Fe3O4 film 3B. The thus obtained ferromagnetic γ-Fe
The crystal grain size of 2O3 was 800, the coercive force was 3000e, the saturation magnetization was 340 emu/cc, and the squareness ratio was 0.78.

On the other hand, the region 3A of the α-Fe2O3 thin film that is not irradiated with the laser beam does not change to Fe704 even after the subsequent heat treatment in the air. -Fe, remains as 03. Strictly speaking, α-Fe, 03 is weakly ferromagnetic, but its magnetism can be considered almost paramagnetic. Therefore, the γ-Fe2O3 and α-Fez obtained in this way
In a recording medium in which 03 alternately form concentric circles, the γ-Fe2O3 area 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 carried out 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 doing this. 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. Further, once recording is completed, the recording 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, Cr,
Those with a base of Au or AfL, 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 10-OmW is used, and a laser beam of 5 to 25 JA! is applied onto the film surface. Light can be focused on the diameter.

When heat-treating an α-Fe2O3 film with a laser beam, the film depends on factors such as the power density of the laser beam on the film surface, the speed of movement of the medium with respect to the beam during heat treatment, the thermal conductivity of the substrate, the composition of the film, and the light absorption rate of the film. temperature varies greatly.

Among these conditions, once the film and substrate are determined in particular, it is possible to control the temperature of the film only by 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, thus making it possible to (The reduction temperature when the J4 film is subjected to laser beam heat treatment in a reducing atmosphere can be set freely, and as a result, crystallographic and magnetic properties can be easily controlled over a wide range.

Table 1 shows the manufacturing conditions of Sample No. 1, which is an example described above, and Sample Nos. 2 to 7 having different manufacturing conditions, and Table 2 shows the magnetic properties of the obtained ferromagnetic molecule -Fe2O3. In addition, so far weakly ferromagnetic α-Fe with a corundum structure has been used.
2-03 and ferromagnetic Fe3O4 having a spinel structure and its manufacturing method have been basically described. ,Os,T.
i.

Even if elements such as Cu, V, Si, Au, and Ru are contained, the wood quality of the present invention does not change at all. Sample number 6 in Table 1 is Go
Sample No. 7 is an example in which Ti-Cu-Go 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 moves once 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 roughing. 1... Non-magnetic substrate. 2... Base layer. 3-a Fe2O3 film, 3A--・a-Fe2O3 ff4 region, 3Fh-y
-Fe103 region. (A) Figure 1

Claims (1)

[Scope of Claims] 1) A non-magnetic substrate, and regions formed on the substrate and made of γ-Fe_2O_3 (maghemite) and α-Fe_2O_3 (α-hematite), which are formed alternately in a concentric or spiral shape. A magnetic recording medium comprising an iron oxide thin film having 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, and -Fe_2
By heat-treating the film in which O_3 and Fe_3O_4 coexist in air, the Fe_3O_4 film is converted to γ-Fe_2O.
A method for manufacturing a magnetic recording medium, characterized in that it has a _3 film.