JPH04144922A - Production of cobalt ferrite film - Google Patents

Abstract

PURPOSE:To obtain a ferrite film having perpendicular magnetization direction and suitable for a high-density opto-magnetic recording medium by controlling the substrate temperature, vacuum degree and deposition thickness in the heat- treatment of a substrate having deposited Co and Fe in an oxygen-containing atmosphere. CONSTITUTION:A multilayer metal film is formed by depositing Co and Fe on a substrate heated at >=100 deg.C in ultimate vacuum of 1X10<-7> to 5X10<-7>Torr. The total thickness of Co and Fe layers is controlled to <=200Angstrom . The substrate having the above multilayer metal film is heat-treated in an oxygen-containing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application and Problems] The present invention relates to a method for manufacturing a cobalt ferrite film used in magneto-optical recording media and the like.

[Prior Art] Conventionally, cobalt ferrite films have been manufactured by direct methods such as reactive vacuum evaporation, ion blating, ion assist, sputtering, and CVD, and by the above-mentioned film forming methods and plating methods. : After producing a metal multilayer film of Fe, it is manufactured by a method of heat-treating in an atmosphere containing oxygen, or an indirect method of anodizing the metal multilayer film in an electrolytic solution.

[Problems to be Solved by the Invention] However, most of the cobalt ferrite films produced by the above-mentioned method have the (311)
It becomes a randomly oriented film with strong linear diffraction intensity. This randomly oriented cobalt ferrite film becomes an in-plane magnetized film,
<1 for perpendicular magnetization film used in magneto-optical recording media
00>It is necessary to orient it in the axial direction. Therefore, it has been desired to establish a technique that can arbitrarily control the orientation of a cobalt ferrite film.

The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a method for manufacturing a cobalt ferrite film whose orientation is controlled in the <100> axis direction and has excellent magneto-optical properties.

[Means for Solving the Problems] The present invention provides a method for manufacturing a cobalt ferrite film by laminating Co and Fe on a substrate to form a metal multilayer film, and then heat-treating the film in an oxygen-containing atmosphere. The ultimate degree of vacuum when forming a multilayer film is LX 10-' to 5x 10-' to
This is a method for producing a cobalt ferrite film characterized by controlling the total thickness of two layers of Co and Fe to 200 Å or less.

Examples of the substrate include a glass substrate.

The metal multilayer film laminated on the substrate is a plurality of two-layer films of Co and Fe laminated. Such a metal multilayer film is
For example, the film is formed by a sputtering method, a vacuum evaporation method, an ion blating method, or the like.

The reason for limiting the degree of vacuum achieved during the formation of the metal multilayer film is that the degree of vacuum is LX 10-7 to 5x 10-'tor.
If r is outside the range, the orientation of the metal multilayer film will change to Fe (1
10) The produced cobalt ferrite film becomes (
This is because the 311) plane has a strong random orientation, resulting in an in-plane magnetized film.

The reason for limiting the total thickness of the two layers of Co and Fe in the metal multilayer film is that if the thickness exceeds 200 layers, the orientation of the metal multilayer film will change to the (110) or (211) plane of Fe. This is because the orientation of the cobalt ferrite film becomes strong and the produced cobalt ferrite film becomes an in-plane magnetized film.

The heat treatment process for the metal multilayer film is preferably performed at a temperature of 500° C. or higher.

In the method for producing cobalt ferrite according to the present invention, the ultimate vacuum degree and Co and F during the formation of the metal multilayer film are
In addition to the total thickness of the two layers e, the substrate temperature is set to 100° C. or higher. The reason for limiting the substrate temperature is that if the temperature is less than 100°C, after heat treatment (400)
This is because it becomes difficult to achieve the purpose of easily and reproducibly manufacturing a cobalt ferrite film that functions as a perpendicular magnetization film with strong plane orientation in the <100> axis direction.

[Function] The present inventors conducted research on producing a cobalt ferrite film by heat-treating a metal multilayer film made of laminated layers of Co and Fe in an oxygen-containing atmosphere. We discovered that the structure of the film is inherited by the oxide film. Based on this phenomenon, we have found that by controlling the crystal orientation of the metal film, we can control the crystal orientation of the cobalt ferrite film, which is an oxide film.

Based on the above-mentioned research results, the present invention provides C on a substrate.

When laminating Co and Fe to form a metal multilayer film, the ultimate vacuum level is controlled to LX 10-' to 5X 10-''tr+rr, and the total thickness of the two layers of Co and Fe is controlled to 200 Å or less, and then oxygen By heat treatment in an atmosphere containing it is conceivable that.

That is, the ultimate vacuum level is LX 10-'~5x 10-''t
orr, the orientation of the film changes due to the influence of residual gas in vacuum. This is thought to be due to the fact that residual gas atoms are adsorbed during film formation, increasing the surface density of the lattice planes on which the gas is adsorbed and lowering the surface energy, which stabilizes these lattice planes and allows preferential growth to take place. . Furthermore, when the total thickness of the two layers of Co and Fe is 200 Å or less, the crystal orientation changes. This is because when Fe is deposited first, the substrate temperature is usually b due to the influence of residual gas.
It is thought that this is because the (100) plane of ee is oriented, and when a thin Co film is formed thereon, it interacts with the underlying Fe. In addition, when the thickness of the two layers is thinner, Co and Fe
This is also thought to be due to the mutual diffusion of

Furthermore, when forming the metal multilayer film, the ultimate vacuum degree and C
By controlling the total thickness of the two layers of O and Fe and controlling the substrate temperature to 100°C or higher, we can create a cobalt ferrite film that functions as a perpendicular magnetization film with a strong (400) plane oriented in the <100> axis direction. can be manufactured easily and with good reproducibility. This effect is caused by the fact that when the substrate temperature during film formation of Co and Fe is 100°C or higher, the adhesion, re-evaporation, and movement of metal atoms on the substrate surface become large and agglomeration tends to occur, which is one of the island-like structures of the film. One becomes almost spherical. This is considered to be due to a change in the orientation of the film.

〔Example〕

Examples of the present invention will be described in detail below.

Example 1 First, the ultimate vacuum degree of the vacuum chamber before film formation was set to 7.6X.
1O-8torr%Co and Fe film thickness ratio is l:2(Co
; 1B, 5 people, F e ; 33.5 people) C
The number of laminated o / F e two-layer films was 40, the substrate temperature was room temperature, 100''C, 1200℃, and 300℃ under the following sputtering conditions on a glass substrate (trade name: Corning 7059, manufactured by Corning Corporation). A multilayer film was fabricated.

[Sputtering conditions] Sputtering gas; A Sputtering gas pressure; 2 m torr; Sputtering current; 0.2 A; Total film thickness;
Heat treatment was performed for 2 hours.

Each oxide film manufactured on a glass substrate by such a process (substrate temperature, room temperature, 100℃, 200"C, 1300℃
) are shown in FIGS. 1 to 4, respectively, in the in-plane direction and the perpendicular direction.

As is clear from Figures 1 to 4, as the substrate temperature increases during multilayer film formation, τ, the residual magnetization of the vertical magnetic hysteresis curve, and the coercive force all increase, and the substrate temperature increases to 100°C. It can be seen from the above that the magnetic properties in the vertical direction become stronger.

On the other hand, FIG. 5(A) shows the X-ray diffraction pattern of the multilayer film when the multilayer film was formed with the substrate temperature at room temperature, and the X-ray diffraction pattern of the oxide film obtained by heat-treating the multilayer film in the air. The patterns are shown in the same figure (B).

Figure 6 (A) shows the X-ray diffraction pattern of the multilayer film when the multilayer film was formed at a substrate temperature of 300°C. The diffraction patterns are shown in the same figure (B).

As is clear from FIG. 5(A), the multilayer film formed with the substrate temperature at room temperature shows a strong Fe (110) plane peak, and as shown in FIG. 5(B), the oxide film is It can be seen that the film has a strong random orientation on the (311) plane of cobalt ferrite.

On the other hand, as shown in FIG. 6(A), the substrate temperature was
The multilayer films formed at 0°C have the same strength as each other (F eO), and peaks for the (110) and (200) planes can be seen, and as shown in Figure (B), the oxide film is It can be seen that the (400) plane of cobalt ferrite is oriented in the slightly strong <100> axis direction.

From the above results, by heat-treating a multilayer film formed at a substrate temperature of 100°C or higher in an oxygen atmosphere, (40°C
0) It is found that a cobalt ferrite film suitable as a perpendicular magnetization film oriented in the <100> axis direction with a slightly strong surface can be manufactured.

Example 2 The ultimate vacuum degree before film formation was 7. OX 10-'torr,
1.7x10-'torr, 4. OX 10-'t
A multilayer film was formed and an oxide film was produced in the same manner as in Example 1, except that the temperature was set to 1.8×10-'torr and the substrate temperature was set to room temperature.

The ultimate vacuum level is 7. Figure 7 (A) shows the X-ray diffraction pattern of the multilayer film formed at OX 10-”torr, and the in-plane and perpendicular magnetic hysteresis of the oxide film obtained by heat-treating the multilayer film in the atmosphere. The curves are shown in Figure 8 (B). Figure 8 (A) shows the X-ray diffraction pattern of the multilayer film formed at the ultimate vacuum of 1.7X to -7 torr. The magnetic hysteresis curves in the in-plane direction and perpendicular direction of the oxide film obtained in this manner are shown in the same figure (B), respectively.
Figure 9 shows the X-ray diffraction pattern of the multilayer film formed at r.
A) shows the magnetic hysteresis curves in the in-plane direction and perpendicular direction of the oxide film obtained by heat-treating the multilayer film in the atmosphere (B).
l: Shown respectively. Furthermore, the ultimate vacuum degree is 1.6×
Figure 1(A) shows the X-ray diffraction pattern of the multilayer film formed at 1O-6 torr, and the magnetic hysteresis curve in the in-plane direction and perpendicular direction of the oxide film obtained by heat-treating the multilayer film in the atmosphere. Each is shown in FIG.

7. As shown in FIGS. 7(A) and (B) and FIG. 10(A) and (B). OX 10-”torr, 1.6X 1O
The multilayer film fabricated at an ultimate vacuum of -6 torr was made of Fe (
110) plane, and it can be seen that the magnetic hysteresis curves of these oxide films are strong in the in-plane direction. On the other hand, as shown in FIGS. 8(A) and (B) and FIGS. 9(A) and (B), 1.7X 10''torr, 4. OX
The multilayer film fabricated at an ultimate vacuum of 10-'torr is F.
It can be seen that the magnetic hysteresis curves of these oxide films are strongly oriented in the vertical direction.

From the above results, when forming a multilayer film, two of Co and Fe
By setting the ultimate vacuum to LX 10-' to 5X 10-' torr under the condition that the total thickness of the layer film is 200 Å or less, a film with high magnetic hysteresis characteristics in the perpendicular direction and suitable as a perpendicular magnetization film can be obtained. It can be seen that it is possible to produce an I-curth ferrite film.

Example 3 The ultimate vacuum level before film formation was 5. Co
/ Fe two-layer film total thickness and number of laminated layers is 2000 Å
×1 layer, 000 people × 2 layers, 500 people × 4 layers, 250 people × 8 layers, 200 people XtO layer, 100 people × 20 layers, 5
Seven types of multilayer films of 0λ×40 layers were formed and oxide films were manufactured.

The total thickness and number of laminated layers of the two-layer film is 2000 people x 1 layer,
1000 people x 2 layers, 500 people x 4 layers, 250 people x 8 layers,
200 people x 10 layers, 100 people x 20 layers, 50 people x 40
The X-ray diffraction pattern of each multilayer film formed under the conditions of the first layer is
1(A) to 17(A) respectively, and the X-ray diffraction patterns of each oxide film obtained by heat-treating these multilayer films in the atmosphere are shown in FIGS. 11(B) to 17(B). are shown respectively.

As is clear from FIGS. 11 (A) and (B) to FIG. 14 (A) and (B), the total thickness of the two-layer film of Co and Fe is 200 mm.
The multi-layered film that has been deposited beyond humans is oriented on the (110) plane of Fe, and these oxide films are also (
It can be seen that this is a randomly oriented film that is strong against the 311) plane. On the other hand, as shown in FIGS. 15 (A), (B) to 17 (A), (B), a multilayer film is formed with a total thickness of two layers of Co and Fe of 200λ or less. is Fe(
It can be seen that these oxide films are strongly oriented in the (400) plane of cobalt ferrite, corresponding to the multilayer film.

From the above results, by forming a multilayer film with a total thickness of two layers of CO and Fe of 200 Å or less under a predetermined ultimate vacuum, it is possible to create a perpendicularly magnetized film strongly oriented in the (400) plane. It can be seen that a suitable konorutferrite film can be produced.

[Effects of the Invention] As detailed above, according to the present invention, Co and Fe are deposited on the substrate.
When forming a metal multilayer film by laminating the two layers, the ultimate vacuum degree and the total thickness of the two layers of CO and Fe are controlled to predetermined values, and then the crystals are heated in an atmosphere containing oxygen. It is possible to provide a method for producing a konochrut ferrite film whose orientation is controlled in the <100> axis direction and which is suitable for a high-density magneto-optical recording medium having magnetization in the perpendicular direction. In addition, when forming a metal multilayer film, the ultimate vacuum degree and CO and Fe 2
By controlling the total thickness of the layers and the substrate temperature to predetermined values, and then performing heat treatment in an oxygen-containing atmosphere, the crystal orientation is controlled in the <100> axis direction and magnetization is in the perpendicular direction. A cobalt ferrite film suitable for high-density magneto-optical recording media can be manufactured easily and with good reproducibility.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams showing the in-plane and perpendicular magnetic hysteresis curves of each oxide film formed in Example 1, and Figures 5 and 6 are diagrams showing the magnetic hysteresis curves formed at different substrate temperatures. Diagrams showing the characteristics of multilayer films and their oxide films, Figure 7~
FIG. 10 is a diagram showing the characteristics of the multilayer films and their oxide films in Example 2, which were formed at different ultimate vacuum degrees;
Figures 11 to 17 show the C film formed in Example 3.
FIG. 2 is a diagram showing the characteristics of multilayer films having different total thicknesses of O and Fe two-layer films and their oxide films. Applicant's Representative Patent Attorney Takehiko Suzue Diagram - DIEMLI No. N Double Diagram Diagram 2θ (deg) (A) Domain (A) (A) 2θ (deg+0711 2U (deg)) (A) Flower 16 Diagram (B) Figure 17

Claims (2)

[Claims] (1) After laminating Co and Fe on a substrate to form a metal multilayer film, when manufacturing a cobalt ferrite film by heat-treating in an atmosphere containing oxygen, the substrate temperature at the time of forming the metal multilayer film is set to 100 ℃ or higher, the ultimate vacuum level is 1 x 10^-^
A method for producing a cobalt ferrite film, characterized by controlling the total thickness of two layers of Co and Fe to 200 Å or less. (2) A method for manufacturing a cobalt ferrite film according to claim 1, characterized in that the substrate temperature during formation of the metal multilayer film is 100° C. or higher.