JPS60170027A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable easy increase in the coercive force of an oxide magnetic layer consisting essentially of iron by forming a non-magnetic metallic layer which expands in volume in the stage of solidification as an underlying layer on a non-magnetic base. CONSTITUTION:A non-magnetic metal such as Bi which expands in volume in the stage of solidification is deposited on a non-magnetic base and an oxide magnetic layer consisting essentially of iron is formed thereon. gamma-Fe2O3 and Fe3O4 are usable as the iron oxide magnetic layer. Sb, Ga, Ge, Si, Tl and the alloy, intermetallic compd., etc. thereof in addition to Bi are usable for the non- magnetic metal which expands in volume in the stage of solidification. Coercive force is thus easily increased and the magnetic recording medium for high-density recording of which the magnetic layer is formed of the oxide consisting essentially of iron is easily obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium having oxide magnetism 1- mainly composed of iron.

Background Art and Problems A magnetic recording medium using iron oxide as magnetic J- has been proposed, but the iron oxide itself has a coercive force 11c of up to 3.
Since it is about 000e, ζ is inappropriate for use as a magnetic recording medium for Iu density recording. Generally, Co is made into Co ferrite by adding cobalt Co, and the coercive force 11c is increased due to its large crystal magnetic field. However, it is well known that heating demagnetization and pressure demagnetization occur each time Co is added. In order to compensate for this drawback, several methods have been proposed in which other third elements are added together with Go. However, pressure demagnetization and heat demagnetization become a problem if even a small amount of Co is included, and adding a third element does not essentially solve the problem.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks and provides a magnetic recording medium in which the coercive force 11c of an oxide magnetic layer mainly composed of iron can be crystallized without adding CO.

SUMMARY OF THE INVENTION The present invention is a magnetic recording medium in which a nonmagnetic metal layer that expands in volume upon solidification is formed as a solid layer on a nonmagnetic support.

In the magnetic recording medium of the present invention, the coercive force Nc is improved.

Example The present invention will now be described in detail.

Example 1 With the substrate temperature maintained at 150°C on the glass base ^r
A 300 mm thick old dome layer was deposited by sputtering from a Bi starter for 3 minutes at a pressure of 2 x 10"' Torr and a pressure of 4 x CAr pressure. A Pf3304 target was sputtered at 150 W of RF power for 30 minutes at 10-' Torr to deposit an iron oxide layer to a thickness of 2000. After sputtering, the iron oxide layer was black, similar to the FC1304 target. This iron oxide j- was heated at 350°C in the air.
, thermal oxidation was performed for 1 hour. As a result of X-ray diffraction analysis of the magnetic recording medium having the iron oxide magnetic layer thus obtained, Bll B+20a and 7-Fe2Qa
peak was observed. This magnetic recording medium will be referred to as Example 1.

Comparative Example 1 A Fe3O4 target was sputtered on a glass base with a static pressure of 2 x 1O-JTorr and an RF power of 200- for 30 minutes while the substrate temperature was maintained at 150°C.
A thickness of 2000 ml of iron oxide j- was deposited. This iron oxide layer was thermally oxidized at 300° C. for 1 hour in the air. As a result of examining the magnetic recording medium thus obtained by X-ray diffraction, a peak of γ-pe20i was observed.

This magnetic recording medium is referred to as Comparative Example 1.

The above table shows the results of examining the magnetostatic characteristics of each of the above-mentioned magnetic recording media using a vibrating sample magnetometer (VSM).

As is clear from the results in the table above, Example 1 is Comparative Example I
The coercive force tic is about twice as high as that of the conventional one, and the squareness ratio is also improved. Since the magnetic recording medium of Example 1 can improve coercive force +1c without adding Co, thermal demagnetization,
No effect of pressurized demagnetization.

Note that when forming the iron oxide magnetic layer by sputtering, the effects of the present invention will not be diminished even if the magnetic layer is formed by so-called reactive sputtering, in which metallic iron is used as a target and sputtered at an oxygen partial pressure F.

In addition to γ-Pe203, iron oxide magnetic j-
3O4 can also be used.

°ζ
In addition to B1, Sb, Ga, Ge, Sf, TI, alloys thereof, intermetallic compounds, etc. can be used.

Further, as the nonmagnetic support, a polymer film such as polyethylene terephthalate, polyamide, polyamideimide, polyimide, glass, ceramic, sapphire, or a metal plate whose surface is oxidized can be used.

Effects of the Invention According to the present invention described above, a non-magnetic metal such as Bi which expands in volume during solidification is deposited on a non-magnetic support, and a magnetic oxide film mainly composed of iron is formed on the non-magnetic metal to form a 1ζ magnetic material. By configuring the recording medium, coercive force can be easily increased. Furthermore, the squareness is improved, and a magnetic recording medium for areal density recording in which the magnetic layer is made of an oxide mainly composed of iron can be easily obtained.

Claims (1)

[Claims] A magnetic recording medium "C" in which a nonmagnetic metal layer that expands in volume during solidification is formed on a nonmagnetic support, and an oxide magnetic layer mainly composed of iron is formed on the nonmagnetic metal layer.