JPS5862827A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium for vertical recording with enhanced corrosion resistance and superior recording and reproducing efficiency by forming a film of ''Permalloy '' contg. a specified percentage of O on a substrate and a vertically magnetized film composed chiefly of Co and Cr on the Permalloy film. CONSTITUTION:The 1st magnetic layer 2 having an easily magnetizable axis in the surface and contg. O in Permalloy composed chiefly of Fe and Ni by 20- 80 atomic % of the total number of Fe and Ni atoms is formed on a substrate 1 made of a polymer material or a nonmagnetic metal. A vertically magnetized film 3 composed chiefly of Co and <=30wt% Cr is formed on the layer 2 to manufacture a magnetic recording medium having a 2-layered structure for vertical recording. This recording medium has superior recording and reproducing efficiency especially in a device using a vertical magnetic head provided with an auxiliary magnetic pole 4, and by forming the layer 2 the corrosion resistance is enhanced.

Description

[Detailed description of the invention] The present invention relates to a magnetic recording medium suitable for perpendicular recording.

Generally, a perpendicular recording method is a magnetic recording method that has excellent short wavelength recording characteristics. In this system, a perpendicular recording medium whose axis of easy magnetization is perpendicular to the film surface of the medium is mounted.

When a signal is recorded on such a medium, the residual magnetization is oriented perpendicularly to the film surface of the medium, and therefore, the shorter the signal wavelength, the smaller the demagnetizing field within the medium, and the better the reproduced output. A perpendicular recording medium has a magnetic layer on a substrate made of a polymeric material or a nonmagnetic metal, which is mainly composed of Co and Cr and has an axis of easy magnetization in the perpendicular direction (hereinafter, this magnetic layer is referred to as a Co-Cr perpendicular magnetization film). is formed by a sputtering method or a vacuum evaporation method. Sputtered or vapor-deposited films containing Co and Or as main components have a close-packed hexagonal crystal structure when the amount of Cr is about 30% by weight or less, and the C axis is oriented perpendicular to the film surface. It is also possible to reduce the saturation magnetization until the anisotropic magnetic field in the perpendicular direction becomes larger than the demagnetizing field, making it possible to realize a perpendicularly magnetized film. Further, a Co--Cr perpendicularly magnetized film containing Cr of about 18% by weight or more has excellent corrosion resistance, and almost no change is observed even if it is left in a 60'C 90% atmosphere for 6 months. However, a perpendicular recording medium in which a Co-Cr perpendicular magnetization film is formed directly on a substrate (hereinafter this medium will be referred to as a single-layer film m#-)
Low efficiency when recording and reproducing signals. In order to improve this, a medium with a structure as shown in Figure 1 (hereinafter referred to as 2
layered media) have been developed. A magnetic layer 2 made of permalloy having an axis of easy magnetization in the plane of the film is provided between a substrate 1 made of a polymeric material or a nonmagnetic metal and a perpendicularly magnetized Co--Cr film 3. Note that permalloy is a general term for alloys whose main components are Fe and 7VJi. Using a double-layer film medium with such a structure improves recording and reproducing efficiency compared to a single-layer film medium, especially when recording and reproducing signals using an auxiliary pole-excited vertical head as shown in Figure 2. , an efficiency improvement of approximately 2° dB was observed both during recording and during playback. In addition, the second
In the figure, 4 is a main magnetic pole made of a ferromagnetic thin film, 6 is an auxiliary magnetic pole made of a ferromagnetic core around which an excitation winding 6 is wound,
The medium is sandwiched between the two magnetic poles.

・As mentioned above, the dual-layer media can achieve extremely superior recording and reproducing efficiency compared to single-layer media, but the Tsuku-□ Malloy film has poorer corrosion resistance than the C0-Cr perpendicular magnetization film.
Because the two membranes are in direct contact with each other, local batteries are likely to occur and corrosion is likely to occur. Co-C which actually contains 20% by weight of KCr
r A single-layer film medium consisting only of a perpendicularly magnetized film and a two-layer film medium consisting of a Co-Cr film and a permalloy film having the same composition were placed in an atmosphere of 60°C and 90°C at the same time, and after being left for one month, the medium surface was When observed with an optical microscope, no change was observed in the single-layer film medium, but in the double-layer film medium.
・There were spots of rust.

The present invention provides a perpendicular recording medium, which is a two-layer film medium, and which has superior recording and reproducing efficiency than a single-layer film medium and has improved corrosion resistance. The present invention will be explained below using VC drawings.Q In two-layer film media, permalloy films are generally formed by sputtering or vacuum evaporation, but when oxygen is introduced during formation, the resulting film contains oxygen inside. become a state. Analysis by electron diffraction reveals that such a film is a mixture of permalloy and oxide. Figure 3 shows the relationship between the average value of oxygen in the film and the amount of oxygen introduced, which was analyzed using Auger electron spectroscopy for a film prepared by introducing oxygen during vapor deposition using vacuum evaporation method 11. From this figure, it can be seen that the larger the amount of oxygen introduced during vapor deposition, the more oxygen in the film increases. Films containing oxygen have better corrosion resistance than films that do not contain oxygen, and
When the r film is formed thereon, corrosion due to local batteries between the two films is also reduced. However, when permalloy contains oxygen, its magnetic permeability μ and saturation magnetization Ms decrease, resulting in deterioration of its magnetic properties. FIG. 4 shows the relationship between μ and Ms and the average value of oxygen in the film.

It is clear from this figure that as the amount of oxygen in the film increases, the magnetic properties deteriorate. Therefore, it was experimentally confirmed how the recording and reproducing efficiency changes when μ and Ms decrease in a permalloy film used as a two-layer film medium. The experimental results 11+ll are shown in Figure 5r.

The solid line 7 and the broken line 8 are the recording efficiency and reproduction efficiency, respectively. The composition of the permalloy film as the two-layer film medium used in the experiment was 20 vIt% Fe and 80tt% Ni.
The composition of the Co-Cr perpendicular magnetization film is 80 wt Co.
%, Cr is 2°y+Jt%. All film thicknesses are 0.
．． It is 16 μm.

Further, as a recording/reproducing head, an auxiliary magnetic pole excitation type vertical head shown in FIG. 2 was used to record and reproduce a sine wave having a wavelength of 0.6 μm. It can be seen from FIG. 5 that as the amount of oxygen in the permalloy film increases, the recording efficiency and reproduction efficiency deteriorate. In particular, when (number of oxygen atoms)/(number of Fe atoms + number of Ni atoms) becomes 80%, the recording efficiency is 20% compared to the case without oxygen.
dB, the reproduction efficiency decreases by 18 dB, and the efficiency becomes comparable to that of a single-layer film medium. Therefore, in order to maintain its superiority as a two-layer film medium, it is safe to keep the ratio (number of oxygen atoms)/(number of Fe atoms+number of Ni atoms) to 80% or less.

Regarding corrosion resistance, the two-layer film medium was placed in a 60°C 90% atmosphere for one month and the medium surface was observed using an optical microscope. As a result, (number of oxygen atoms) / (number of Fe atoms + number of Ni atoms)
In films with a content of less than 20%, spot-like rust was generated, but in films with a content of 20% or more, almost no change was observed.

Note that almost the same results as above were obtained even when the composition of the permalloy film was changed.

According to the present invention, as described above, recording/reproducing efficiency and corrosion resistance can be improved by using a permalloy film containing oxygen in an amount of 20% or more and 80% or less of the total number of Fe and Ni atoms in a two-layer film medium. An excellent perpendicular recording medium is obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magnetic recording medium, FIG. 2 is a partially sectional front view showing how recording and reproduction are performed using the magnetic recording medium, and FIGS. 3 to 6 are for explaining the present invention. In the diagram,
Of these, Figure 3 shows the relationship between the oxygen introduction needle and the oxygen content in the permalloy film during deposition of the permalloy film, which is an example of the first magnetic layer, and Figure 4 shows the relationship between the oxygen content and the permeability in the permalloy film. The relationship between magnetic property and saturation magnetization is shown, and FIG. 5 also shows the relationship between oxygen content and recording/reproducing efficiency in the permalloy film. 1...substrate, 2...magnetic layer made of permalloy, 3...perpendicular magnetization film. Name of agent: Patent attorney Satoshi Nakao and one other person
Figure 41 @ Figure 2 Figure 3 1 Fx layer 1% eyn At (timin) Figure 4 D1'' -V er・ Figure 5 50, Igen I (Cr11-VCc) ν

Claims (1)

[Claims] A first magnetic layer mainly composed of Fe and Ni is formed on a substrate and has an easy axis of magnetization in the film plane, and further has an easy axis of magnetization perpendicular to the film surface. Has C. In a magnetic recording medium in which a second magnetic layer mainly composed of F and Cr is formed, the first magnetic layer has F in number of atoms.
A magnetic recording medium characterized in that it contains oxygen in an amount of 20 or more and 80% or less of the total number of atoms of e jl N i.