JPH03212813A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To increase saturation magnetization, coercive force and squareness ratio by providing a magnetic layer on a nonmagnetic substrate so that the magnetic layer consists of a mixture of alpha-Fe and Fe3O4 and has a specified volume ratio of alpha-Fe and thickness. CONSTITUTION:A magnetic layer comprising a mixture of alpha-Fe and Fe3O4 with the volume ratio x of alpha-Fe satisfying 0.4<x<0.6 and having <=500 Angstrom thickness is provided on a nonmagnetic substrate. If the volume ratio x is less than 0.4, the saturation magnetization decreases, while with over 0.6, the coercive force and squareness ratio decrease. If the thickness exceeds 500 Angstrom , the coercive force decreases. Thereby, the obtd. medium has high saturation magnetization, large coercive force and squareness ratio and high mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium with an improved iron-based magnetic layer and a method for manufacturing the same.

[Prior Art] Attempts have been made to manufacture magnetic recording media with high magnetic recording density using Fe, which has a high saturation magnetization. For example, an evaporation source is installed on a non-magnetic substrate obliquely to the surface of the substrate, and Fe evaporation particles are incident from the evaporation source obliquely at an angle of 60 to 80° with respect to the normal direction of the substrate. A method of manufacturing a magnetic recording medium is known in which a magnetic layer is formed using a method of manufacturing a magnetic recording medium. According to this oblique vapor deposition method, shape anisotropy occurs in the layer structure due to the self-shading effect, and the coercive force increases (several 100 to 10,000 e) in the direction parallel to the incident plane of the vaporized particle flow.
L, it becomes possible to form a Fe magnetic layer with a good squareness ratio.

[Problems to be Solved by the Invention] However, the Fe magnetic layer formed by the conventional method described above has a rough layer structure and a low density, so that the saturation magnetization (4πM s ) decreases to 10 kG or less. Moreover, there was a problem in that the mechanical strength of the magnetic layer also decreased.

The present invention has been made to solve the above-mentioned conventional problems, and includes a magnetic recording medium with high saturation magnetization (4πM s ), high coercive force, and large squareness ratio, and a method for easily manufacturing such a magnetic recording medium. This is what we are trying to provide.

(Means for Solving the Problems) A magnetic recording medium according to the present invention has α-F on a non-magnetic substrate.
It consists of a mixture of e, Fe, O, and the volume ratio of α-Fe is
thickness 50 with a composition of 0.4 < x < 0.8
It is characterized by providing a magnetic layer with a thickness of 0 Å or less.

Examples of the nonmagnetic substrate include glass, Afi alloy, and the like.

The α-Fe and Fe50. The reason for limiting the volume ratio X of α-Fe in the mixture is that when X is less than 0.4, the saturation magnetization (4πM s ) decreases, whereas when X exceeds 0.6, the coercive force and squareness decrease. This is because the ratio becomes smaller.

The reason why the thickness of the magnetic layer is limited is that the thickness is 50 mm.
This is because when the number exceeds 0, the coercive force decreases.

Further, in the method for manufacturing a magnetic recording medium according to the present invention, iron is deposited on a non-magnetic substrate, and at the same time, an oxygen ion beam is irradiated on the substrate at an angle of 30@ or more with respect to the normal direction of the surface of the substrate. consists of a mixture of α-Fe, Fe, O, and the volume ratio X of α-Fe is 0.4 < x < 0.6.
This method is characterized by forming a magnetic layer having a thickness of 500 Å or less and having a composition of .

The reason for limiting the irradiation angle of the oxygen ion beam is that if the angle is less than 30° with respect to the normal direction of the surface of the non-magnetic substrate, uniaxial magnetic anisotropy with the easy axis perpendicular to the ion beam incident plane will occur. This is because the magnetic layer cannot be formed within the plane of the magnetic layer. Note that, from the viewpoint of efficiently introducing oxygen ions during film formation, it is desirable that the upper limit of the irradiation angle of the oxygen ion beam is 70''.

During the Fe vapor deposition and oxygen ion beam irradiation,
The higher the deposition rate and the higher the heating temperature of the non-magnetic substrate,
The amount of α-Fe in the formed magnetic layer increases. Therefore, by controlling the deposition rate and the heating temperature of the nonmagnetic substrate, it is possible to form a magnetic layer having the desired composition described above.

C action] According to the present invention, α-Fe and Fe3O4 are formed on a non-magnetic substrate.
The saturation magnetization (4πM
s) is 12~14kG, coercive force (Hc) is 4QO~
6000 e and a squareness ratio (S) of ~0.8, it is possible to obtain a magnetic recording medium which has excellent magnetic properties and has an improved mechanical strength of the magnetic layer.

According to the method of the present invention, iron is deposited on a non-magnetic substrate and, at the same time, an oxygen ion beam is irradiated at an angle of 30'' or more with respect to the normal direction of the surface of the substrate, thereby depositing α- A thin layer made of a mixture of Fe and Fe3O4 is formed, and uniaxial magnetic anisotropy with the easy axis perpendicular to the plane of incidence of the oxygen ion beam can be formed in the plane of the thin layer. Based on the relationship between the vapor deposition rate and the heating temperature of the substrate and the amount of α-Fe in the magnetic layer, by controlling the vapor deposition rate and the heating temperature of the non-magnetic substrate, the volume ratio X of α-Fe is 0. .4<x<0.
A magnetic layer having a composition of No. 8 and a thickness of 500 Å or less can be formed. As a result, as mentioned above, the saturation magnetization (4πMs) is 12 to 14 kG.

Coercive force (Hc) is 400-6000 e, squareness ratio (S
) can produce a magnetic recording medium with excellent magnetic properties of ~0.8. Moreover, by forming the magnetic layer while irradiating it with an oxygen ion beam, it is possible to manufacture a magnetic recording medium having a magnetic layer that has high adhesion to the substrate, high density, and excellent mechanical strength.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to FIG.

FIG. 1 is a schematic diagram showing a film forming apparatus used in this example. 1 in the figure is a vacuum chamber.

Inside this chamber 1, an electron beam evaporation source (E
B evaporation source) 2 is arranged. A substrate holder 3 is arranged in the chamber 1 located above the EB evaporation source 2. A Kauffman type ion source 4 is installed on the side wall of the chamber 1 so that the irradiation angle of its ion beam is 45'' with respect to the normal direction of the substrate held in the holder 3. An exhaust pipe 5 connected to a vacuum exhaust system (not shown) is provided at the bottom of the chamber 1.

Next, a method for manufacturing a magnetic recording medium will be described using the film forming apparatus shown in FIG. 1 described above.

Example 1 First, Fe powder 6 is stored in the EB evaporation source 2 in the vacuum chamber 1, and after holding, for example, a glass substrate 7 in the substrate holder 3, an evacuation system (not shown) is activated, and the evacuation pipe 5 is passed through the chamber l. Exhaust the gas inside IX 10-'tor
The degree of vacuum was set to r. Next, EB is
The e-powder 6 was irradiated to evaporate Fe, and at the same time an oxygen ion beam was irradiated from the Kauffman ion source 4 to form a thin Fe-0 layer with a thickness of 500 on the glass substrate 7.
Seed samples were prepared. In this film-forming process, the incident angle of the oxygen ion beam is 4
5°, and the current density of the oxygen ion beam was 1 mA/c1.
12. The accelerating voltage was kept constant at 600 V, and the substrate temperature and film formation rate were set to the conditions shown in Table 1 below.

The α-Fe volume ratio and magnetic properties of the Fe-0 thin layers in the 12 types of samples obtained were investigated. The results are also listed in Table 1. In addition, Hc, S in Table 1
, are the in-plane coercive force and squareness ratio, respectively, measured in a direction parallel to the ion beam incidence plane. Also, HO2,
S2 is 1l in the direction perpendicular to the ion beam incidence plane.
FI is the in-plane coercive force and squareness ratio.

As is clear from Table 1 above, in sample No. 7.8, in which the Fe-0 thin layer was deposited with the α-Fe volume ratio within the range of the present invention (0-, 4 to 0.6), the ion beam incident Both the in-plane coercive force and the squareness ratio measured in the direction perpendicular to the plane increase, and the saturation magnetization (4yr M s ) increases by ~1.
4kG, coercive force (Hc) ~5000e, squareness ratio (
It can be seen that it has magnetic properties suitable for use as a magnetic recording medium, with S) ~0.8.

Example 2 A film with a thickness of 300 to 1000 was formed in the same manner as in Example 1, except that the film forming apparatus shown in FIG.
A thin layer of Fe-0 was deposited on a glass substrate.

The in-plane coercive force (H
O2) was investigated. The results are shown in FIG. 2, which shows the relationship between the thickness of the Fe-0WJ layer and the coercive force (HO2). As is clear from FIG. 2, a high coercive force of 5000 e or more can be obtained in an Fe-0 thin layer with a thickness of 500 Å or less.

[Effects of the Invention] As detailed above, according to the present invention, saturation magnetization (4πM
g), a large coercive force, a large squareness ratio, and a high mechanical strength, as well as a method for easily manufacturing such a magnetic recording medium.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the film forming apparatus used in this example, Figure 2 is a schematic diagram showing the film forming apparatus used in this example.
The figure is a characteristic diagram showing the relationship between the thickness of the Fe-0 thin layer and coercive force (HC2). ■...Vacuum chamber, 2...EB evaporation source, 4...
Kaufmann type ion source, 7... glass substrate.

Claims (2)

[Claims] (1) Consisting of a mixture of α-Fe and Fe_3O_4 on a non-magnetic substrate, the volume ratio x of α-Fe is 0.4<x<0.6
1. A magnetic recording medium comprising a magnetic layer having a thickness of 500 Å or less and having a composition of: (2) At the same time as depositing iron on a non-magnetic substrate, an oxygen ion beam is irradiated at an angle of 30° or more with respect to the normal direction of the substrate surface to deposit α-Fe and Fe_3O_ on the substrate.
4, the volume ratio x of α-Fe is 0.4<x
A method for manufacturing a magnetic recording medium, comprising forming a magnetic layer having a thickness of 500 Å or less and having a composition of <0.6.