JPS61255533A - Vertical magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To enhance the saturation magnetization of the titled medium and to prevent the generation of microcracks by forming a vertically magnetized film consisting essentially of an Fe-Cr alloy contg. a specified amt. of Cr and having a saturation magnetization value on a nonmagnetic substrate. CONSTITUTION:A vertically magnetized film having vertical magnetic aniso tropy, consisting essentially of an Fe-Cr alloy contg. 20-30atom% Cr and having 350-700emu/cc saturation magnetization is formed on a nonmagnetic substrate through a high-permeability magnetic material or without the material to form a magnetic recording medium. Into the magnetic recording medium, <=10atom% at least one kind among Ni, Co, Bi, a platinum-group element, Zr, Ta, Nb, W and C is preferably incorporated. The magnetized film is formed by using an alloy consisting essentially of Fe-Cr as a target and sputtering the target in an inert gas. The bias voltage to be impressed at that time is preferably regulated to -50--500V on an earth basis. Consequently, an Fe-Cr vertically magnetized film having high saturation magnetization of 350-700emu/ cc and without any microcracks is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to improvement of perpendicular magnetic recording media mainly made of Fe-Cr alloy, and particularly perpendicular recording media with large saturation magnetization and no microcracks. and its manufacturing method.

[Background of the invention]

Perpendicular magnetic recording is a method that records by magnetizing in the direction perpendicular to the film surface, and is considered suitable for high-density magnetic recording because it causes less recording demagnetization due to demagnetizing fields than the current longitudinal recording method. ing.

In order to realize this perpendicular magnetic recording, a perpendicular magnetization film having an axis of easy magnetization perpendicular to the magnetic film surface is required as a recording medium. As a magnetic film having such magnetic properties, an Fe-Cr alloy film with a Cr content of 33 to 40 atomic % and a saturation magnetization value of 100 to 300 emu/cc is known (this will be discussed in Chapter 3). (Described in the 8th Japan Society of Applied Magnetics Academic Conference Abstracts P9 (1984, November)).

However, since this material has a high Cr content of 33yK%, it has a problem in that the saturation magnetization is as low as about 300 e+su/g or less, and the reproduction output is small. In addition, since the Cr content is as high as 33g%, Fe-
It has become clear that the Cr alloy film is brittle and has the problem that microcracks are likely to occur in the magnetized film.

[Purpose of the invention]

An object of the present invention is to provide an Fe--Cr perpendicular magnetic recording medium that has a large saturation magnetization value by reducing the Cr content and is free of microcranks, and a method for manufacturing the same.

[Summary of the invention]

The reason why an Fe--Cr magnetic alloy film containing 33 atomic % or more of Cr becomes a perpendicular magnetization film is considered as follows. Fe-33M produced by magnetron sputtering method
In the Cr magnetic alloy film, an amorphous or microcrystalline Fe--Cr alloy having a columnar structure is arranged perpendicularly to the film surface, and each column is magnetically isolated by nonmagnetic bcccr segregation. This is thought to be a cause of perpendicular magnetic anisotropy.

The magnitude of this perpendicular magnetic anisotropy (K,) is the magnetostatic energy (2πIs'', Is
: saturation magnetization), the film becomes a perpendicularly magnetized film.

In the known method, a perpendicularly magnetized film cannot be obtained if the Cr content is less than 33 atomic %. This is presumed to be due to the large diameter of the column mentioned above.

Therefore, as a result of investigating the relationship between the column diameter and the content of Cr in which the Fe-Cr alloy becomes a perpendicularly magnetized film, we found that the column diameter was 0.0
By setting it to 1 to 0.1 μm, the Cr content is 20 to 20.
It has become clear that the Fe--Cr alloy film becomes a perpendicularly magnetized film even at a concentration of 30 atomic %.

A particularly effective method for controlling the column diameter is to apply a voltage of -50 to -500V to the substrate with respect to ground when performing physical vapor deposition (sputtering, vapor deposition, etc.) of the Fe-Cr alloy film. .

The substrate temperature may be anywhere from 20 to 200°C, but may be from 50 to 200°C.
A temperature between 150° C. is more preferable since microcracks do not occur.

Figure 2 shows the effective perpendicular magnetic difference of the Fe-Cr alloy film produced by applying a bias voltage of -150 μm to the substrate with respect to ground when producing the Fe-Cr alloy film using the high-frequency sputtering method. The relationship between the magnitude of orientation (K u = K + 2π 52) and the saturation magnetization and Cr content of the film was shown. The column diameter of these membranes was 0.02-0.05 μm.

As is clear from FIG. 2, by applying a bias voltage and controlling the column diameter to 0.02 to 0.05 μm, the Cr content is 23 atomic % to 40 atomic % Fa=C:
The r alloy film becomes a perpendicular magnetization film.

Further, the saturation magnetization of a Fe--Cr alloy film with a Cr content of 23 to 28 atomic % is 400 to 650 emu/cc, which is larger than the known value (100 to 300 emu/cc).

Furthermore, no microcracks were observed on the film surface in any of the Fe--Cr alloy films with a Cr content of 30 atomic % or less. In other words, during high-frequency sputtering, one layer is applied to the substrate.
Apply a DC bias of 50V and adjust the column diameter to 0.02~
By controlling the thickness to 0.05 μm, a perpendicularly magnetized Fe—Cr film with large saturation magnetization and no microcracks can be obtained.

The Fe-Cr alloy film of the present invention contains 10 atomic % or less of Ni.
, Co, Bi, platinum group elements, Zr, Ta.

If at least one of Nb, W, and C is contained, Fe-
It is more preferable since it is effective in improving the corrosion resistance of the Cr alloy and preventing the generation of microcracks.

Furthermore, it is preferable to form a high magnetic permeability film under the Fe--Cr alloy film, since this will approximately double the reproduction output.

The thickness of the high magnetic permeability film is preferably 0.3 to 2 μm.

This range is preferable because the reproduction output increasing effect is small when the thickness is 0.3 μm or less, and the reproduction output increasing effect is saturated when the thickness is 2 μm or more. Materials for high magnetic permeability films include ferrite, permalloy, and sendust.

(Fe, Co, Nx) (Sx* By Ct P
+AQ-B) type amorphous alloy, (Fe, Go, N1)-(
Hf, Zr, Y, Ti, Nb, Ta, W, V.

Mo, Cr) based amorphous alloy, Fe-8i, Fe-5i-
Polycrystals such as Ru, F8xsNz and non-magnetic films (SiO2
, AQ203, etc.), magnetic film (Go.

It is possible to use a material known as a material for a magnetic head, such as a laminated film of N x + permalloy, etc.).

The base layer of the single-layer Fe-Cr alloy film includes SnO,
It is preferable to use the above because a vertical Fa--Cr alloy film with high saturation magnetization can be obtained.

Further, the distance between the nearest atoms of the conductive base film is 1.8 to 2.
The two materials are more preferable because they have a great effect as a base film.

In the case of a so-called two-layer film that uses a high magnetic permeability film, a conductive underlayer film with a nearest neighbor atomic distance of 1.8 to 2.2 is formed between the high magnetic permeability film and the Fe-Cr perpendicular magnetization film. It is more preferable to form the Fe--Cr perpendicularly magnetized film between the two layers because the saturation magnetization of the Fe--Cr perpendicularly magnetized film can be increased.

The high magnetic permeability film and the Fe-Cr alloy film can be formed using manual sputtering methods such as high frequency sputtering, magnetron sputtering, and ion beam sputtering, and vapor deposition methods.

Any method such as a plating method or a chemical vapor deposition method may be used, but a physical vapor deposition method such as a sputtering method or a vapor deposition method is more preferable because it facilitates film formation. Among these, the sputtering method is more preferable because the film composition can be easily controlled.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples, but the Examples are not intended to limit the present invention.

Example 1 Using the RF sputtering apparatus shown in FIG. 1, an Fe--Cr alloy film was formed on a non-magnetic substrate. In Figure 1,
Reference numeral 1 denotes a non-magnetic substrate which has a structure to which a bias voltage of 1500 V-OV can be applied.

2 is a sputter target and the target is 13.5M.
It has a structure that allows radio frequency (RF) waves of Hz to be applied.

3 is a needle valve to control the flow rate of sputtering gas such as Ar! 51! It has a structure that can be adjusted.

Using the above apparatus, Ar of 5 X 10-” Torr was applied using a Fe-Cr alloy target of 100 Ilfiφ.
An Fe-Cr alloy film with a film thickness of 0.3 μm was deposited on five large plates under pressure.

Note that a bias voltage of -150 V was applied to the substrate with respect to ground.

The Orr content of these Fe-Cr alloy films and the saturation magnetization (Is) measured by a sample vibrating magnetometer (V SM)
and Ku measured with a magnetic torque measuring device (= 2πI
s”) is shown in FIG.

As a comparative example, FIG. 2 also shows a case where no bias was applied.

As is clear from Figure 2, during RF sputtering,
By applying a bias voltage of 0 V, the Fe--Cr alloy film with a Cr content of 23 to 40 atomic % becomes a perpendicularly magnetized film. Further, Fe with a Cr content of 23 to 28 at%
- The saturation magnetization of the Cr alloy film is 400-6
50eIIu/cc, known value (100~30
0e+su/cc). Also, 30 atomic%
No microcracks were observed on the film surface in any of the Fe-Cr alloy films with the following Cr contents.

Example 2 Fe-5 ff was produced in the same manner as in Example 1, except that Fe-〇r gold alloy containing 5 at% Ni was used as the target and the bias voltage was set to -500V.
An alloy film of i%Ni-20M%Cr was fabricated. The magnetic properties of this film are as follows.

Perpendicular coercive force (Hc.) near 000e, in-plane coercive force (HcI): 1500e, saturation magnetization (I
s): 695emu/cc, Vertical squareness ratio (Ir./Is): 0.08, In-plane squareness ratio (Ir,/Is): 0.05, Effective perpendicular magnetism Anisotropy constant (Ku): 8.6 x 1 0
'erg/cc, column diameter: ~0.02 μm, microcracks: none.

As is clear from this result, Fe − Cr−
The Ni alloy film is a perpendicular magnetization film, and the saturation magnetization is also about 70.
It is large at 0 erau/cc.

Example 3 Fa-
30 atomic% Cr-10jK %C.

An alloy film was prepared. The characteristics of this film are as follows.

Hc: 4000e', Has: 1200c,
Is: 354cmu/cc, I
rt/Is: 0.10, Ir,/I
s: 0.04, Ku: 5.3 x 10”e
rg/cc, column diameter: ~0.1 μm, microcracks: None.

As is clear from this result, Fa -Co -Cr
The alloy film is a perpendicular magnetization film, and the saturation magnetization is also about 350 emu.
It is large at /cc. Further, no microcracks were observed.

〔Effect of the invention〕

As is clear from the above explanation, the Cr content is 20~
By using 30 atomic % and a column diameter of 0.02 to 0.1 μm, an Fe-Cr perpendicular magnetization film with a large saturation magnetization of 350 to 7 f) Oemu/cc and no microcracks can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a high frequency spackle apparatus used for producing a Fe--Cr thin film in one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the effects of the present invention. 1... Nonmagnetic substrate, 2... Sputter target, 3
... Needle valve, 4... Change curve of saturation magnetization of Fe-Cr alloy film produced by applying bias voltage, 5... Fe produced by applying bias voltage
Change curve of effective perpendicular anisotropy (K u ) of Cr alloy film, 6...Fe-C produced by conventional method (no bias)
Change curve of saturation magnetization of r film, 7... Change curve of Ku of Fe-Cr film produced by conventional method. Figure 2 Cr content (elevation j%)

Claims (1)

[Claims] 1. Fe-Cr having perpendicular magnetic anisotropy deposited on a non-magnetic substrate with or without a high permeability magnetic material.
In a magnetic recording medium mainly composed of an alloy, the Cr content is 20 to 30 at% and the saturation magnetization value is 350 to 700e.
A perpendicular magnetic recording medium characterized in that it is mu/cc. 2. In claim 1, the magnetic recording medium contains N.
i, Co, Bi, platinum group elements, Zr, Ta, Nb, W,
A perpendicular magnetic recording medium comprising 10 atomic % or less of at least one of C. 3. A method for producing a perpendicular magnetic recording medium, which comprises performing sputtering using an alloy mainly composed of Fe-Cr as a target in an atmosphere containing an inert gas. 4. A method for manufacturing a perpendicular magnetic recording medium according to claim 3, characterized in that a bias voltage of -50 to -500 V is applied with reference to ground during sputtering or vapor deposition.