JP3023227B2 - Device for perpendicular magnetization and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for perpendicular magnetization suitable for high-density magnetic recording, magneto-optical recording and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A perpendicular magnetic film has attracted attention as a high-density recording medium because it has a much larger recording capacity than a conventional horizontal magnetic film. As the perpendicular magnetization film, for example, utilizing the large uniaxial crystal magnetic anisotropy of Co,
It is known that the M _s point is lowered by adding o, W, Ru or the like, and the crystal magnetic anisotropy constant is increased as compared with the self-demagnetizing field. It is also known to use a thin film of ferrite, Ba ferrite, or the like formed on a substrate surface by sputtering ferrite, Ba ferrite, or the like on the substrate as the perpendicular magnetization film.

Further, an anodic oxide film formed on the surface of an Al substrate may be used for forming a perpendicular magnetization film (Mitsuo Matsumoto, published by Kyoritsu Shuppan Co., Ltd. on March 1, 1990, "Magnetic Recording" Engineering, pp. 116-117). The anodic oxide film has a structure with fine holes opened on the surface,
A perpendicular magnetization film is formed by depositing a ferromagnetic material in the fine holes by an electrodeposition method.

[0004] However, the surface of the Al substrate is a place where the influence of the history of casting, rolling and the like is greatly exhibited. Therefore, the film formed by the anodic oxidation treatment also tends to have many defects under the influence. In order to suppress the occurrence of this type of defect, recently, an Al layer is formed on the substrate surface by vapor deposition, and a perpendicular magnetization film is formed on the deposited Al layer.

[0005]

The aluminum layer formed by the vapor deposition method exhibits a state in which aggregates of fine particles are deposited on the surface of the substrate, and can be said to be crystallographically non-directional. Further, it is a coating layer having many pores therein. Therefore, when a hole extending in a direction perpendicular to the substrate surface is formed in the aluminum layer by etching or the like, it is difficult to obtain a hole having a uniform diameter. Further, in a portion containing impurities and the like, etching proceeds or delays preferentially, and the cross-sectional shape of the hole becomes irregular. Moreover, due to the presence of the pores, the etching proceeds in a direction parallel to the surface of the base, and a branched hole is easily formed. Such deterioration of the shape characteristics causes an irregular distribution of the ferromagnetic material filled in the hole, and lowers the reliability of information recording.

In addition, it is difficult to make the thickness of the formed aluminum layer constant by the vapor deposition method. Therefore, the length of the hole extending in the vertical direction from the substrate surface, and eventually the amount of the ferromagnetic material filled in the hole is locally different,
This causes noise when performing high-density recording.

The present invention has been devised to solve such a problem, and an electroplating method is used to form an aluminum layer having excellent crystal growth directionality and film thickness uniformity. It is another object of the present invention to provide a highly reliable perpendicular magnetization device suitable for high-density recording.

[0008]

In order to achieve the object, a device for perpendicular magnetization of the present invention comprises a substrate made of a non-magnetic material, and an electro-aluminum plating crystal grown in a direction perpendicular to the surface of the substrate. A vertical hole formed in the aluminum plating layer and extending in a direction perpendicular to the surface of the substrate; and a ferromagnetic material filled in the vertical hole.

In this device for perpendicular magnetization, an aluminum plating layer formed by crystal growth on a substrate made of a nonmagnetic material in a direction perpendicular to the surface of the substrate is provided by electroplating, and the aluminum plating layer is formed in a direction perpendicular to the surface of the substrate. It is manufactured by forming a plurality of extending vertical holes in the aluminum plating layer and filling the vertical holes with a ferromagnetic material.

As the base material, non-magnetic materials such as aluminum, aluminum alloy, titanium, titanium alloy and austenitic stainless steel are used. It is also possible to use a non-metallic sheet or film of ceramics, plastics, glass or the like as the base material. In this case, after the surface of the base is metallized by electroless plating or the like, electric aluminum plating is performed.

Means for perforating the aluminum plating layer formed on the surface of the base material include photoetching,
Laser beam irradiation or the like is employed. 5μ hole depth
m or less, and since the aluminum plating layer itself is easy to process in a direction perpendicular to the surface of the substrate, a hole having a constant cross-sectional shape is formed from the surface of the plating layer to the surface of the substrate by any of the methods.

The filling of the ferromagnetic material into the hole is performed by depositing a metal such as Fe, Co, or Ni in the hole by electroplating, electroless plating, or the like. Also, M _s
It is also possible to add Cr, Os, or the like, which lowers the point, to the plating bath to cause these elements to eutect a ferromagnetic material such as Fe, Co, or Ni. Alternatively, an aluminum-plated substrate is immersed in a suspension in which ferromagnetic ultrafine powder such as ferrite or Ba ferrite is dispersed, irradiated with ultrasonic waves to penetrate the ultrafine powder, and then dried. The ferromagnetic material is also filled.

[0013]

[Operation] In electroplating, a plating layer having a uniform thickness is formed in a direction perpendicular to the substrate surface. This plating layer eliminates non-uniformity of the surface layer caused by segregation of alloying elements and impurity elements, solidification structure or rolled structure, and uniformly adjusts the surface.

Further, the crystal growth is controlled by selecting the plating conditions, and a plated layer in which drilling in the vertical direction is easy is formed. For example, when plating is performed at a high current density in a plating bath to which toluene is added, the crystal plane can be aligned with the (111) plane. Therefore, a hole having a uniform hole diameter and depth can be formed at the time of anodic oxidation, etching, or the like.

In addition, since the plating layer having a uniform thickness is formed on the surface of the substrate, the holes formed in the plating layer have a uniform diameter, depth, and the like, and have no defects such as branching. Therefore, when this hole is filled with a ferromagnetic material,
A perpendicular magnetization film having excellent performance and reliability can be obtained.

[0016]

EXAMPLE An aluminum foil having a width of 50 mm and a thickness of 1 mm was used as a substrate. This aluminum foil was subjected to electric aluminum plating using a non-aqueous plating bath under the following conditions.

[0017]

[Table 1]

The obtained plated layer had a substantially uniform thickness with an average thickness of 3 μm and a variation in thickness of 2.8 to 3.2 μm centered at 3 μm, and a thickness deviation of ± 5%. . Also, crystals grew in a direction perpendicular to the surface of the aluminum foil.

Anodized aluminum foil was subjected to anodic oxidation in a 3% by weight oxalic acid solution to form an anodic oxide film having an average thickness of 2 μm on the aluminum plated layer. This anodic oxide film had a vertical hole having a pore diameter of 500 angstroms and a cell diameter of 1000 angstroms. Observation of the test piece surface layer after the anodizing treatment revealed that the formed vertical holes extended in the vertical direction from the surface of the aluminum foil, and no branched horizontal holes were detected. Was. The anodic oxidation was performed under the conditions shown in Table 2.

[0020]

[Table 2]

Then, the aluminum foil having the perforated plating layer was immersed in an Fe precipitation bath, and Fe was precipitated in the holes in the plating layer under the following conditions.

[0022]

[Table 3]

By this precipitation treatment, the hole formed in the plating layer was substantially completely filled with the precipitated Fe. As a result, a ferromagnetic material filling portion extending in a direction perpendicular to the surface of the aluminum foil was formed. Since the ferromagnetic material-filled portion imitated the hole formed in the plating layer, the length in the vertical direction and the cross-sectional area in the horizontal direction were excellent in uniformity.

The characteristics of the obtained device for perpendicular magnetization are as follows. The comparative example is a case in which a ferromagnetic material similarly embedded in an aluminum layer formed by vapor deposition is used as a device for perpendicular magnetization. The aluminum layer obtained by vapor deposition had an average thickness of 3 μm, a maximum thickness of 4 μm, and a minimum thickness of 2 μm, and had a thickness deviation of ± 30%, which was not negligible.

In the test, a test piece was prepared by punching a 3.5-inch disk having an outer diameter of 86 mm and an inner diameter of 25 mm from an aluminum plating-anodized aluminum foil and a vapor-deposited-anodized aluminum foil. Also,
The head used for the measurement was a commercially available button type head for a 5-inch floppy disk, and the gap length was 2.2 μm.
m, the track width was 165 μm, and the number of coil turns was 2 × 130 turns. Then, the disk is inserted into the jacket for the 3.5-inch floppy disk, and the relative speed is 1
Recording and reproduction were performed at m / sec and 100 kHz (50 kBPI). At this time, recording and reproduction characteristics of the same track were examined.
Table 4 shows the results of the survey.

[0026]

[Table 4]

As is apparent from this comparison, in the embodiment of the present invention in which the aluminum layer was formed by electroplating, the homogeneity of the aluminum layer and the directionality of the crystal were utilized, and the aluminum layer was strengthened in a state suitable for perpendicular magnetization. It can be seen that the magnetic material can be filled in the holes in the aluminum layer. On the other hand, in the case where a ferromagnetic material is embedded in an aluminum layer formed by vapor deposition, the non-uniformity of the aluminum layer affects the magnetic recording characteristics.

[0028]

As described above, in the present invention, a ferromagnetic material is embedded in an aluminum layer formed by electroplating on the surface of a nonmagnetic substrate. The electroaluminum plating layer is vertically crystal-grown from the substrate surface, and can be accurately drilled in the vertical direction by etching or laser beam irradiation. Therefore, it becomes possible to fill the hole formed in the aluminum plating layer with the ferromagnetic material with high accuracy. Further, as compared with the vapor deposition method, the aluminum layer formed by the electroplating method has excellent thickness and flatness. Therefore, a device for perpendicular magnetization suitable for high-density magnetic recording or magneto-optical recording can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/858 C25D 11/04

Claims (2)

(57) [Claims] 1. A substrate made of a non-magnetic material and a surface of the substrate
Electric aluminum plating grown in a direction perpendicular to
And the aluminum plating layer, wherein the substrate
Device for perpendicular magnetization, characterized in that it comprises a vertical hole extending in a direction perpendicular, and a ferromagnetic material filled in the vertical hole portion relative to the surface. 2. The method according to claim 1, wherein the surface of the substrate made of a non-magnetic material is
The aluminum plating layer grown vertically in the vertical direction.
A plurality of vertical holes formed in the aluminum plating layer and provided in the aluminum plating layer and extending in a direction perpendicular to the surface of the substrate, and filling the vertical holes with a ferromagnetic material. Device manufacturing method.