JPH02177123A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium with high aspect ratio, high output and low noise by specifying the proportion of nonvalent zinc to bivalent zinc in a magnetic film essentially comprising cobalt and containing zinc. CONSTITUTION:The proportion of nonvalent zinc to bivalent zinc in the magnetic film is specified to (40-60):(60-40), and preferably (45-55):(55-45). If the proportion of nonvalent zinc is less than 40%, the aspect ratio of the magnetic recording medium is too low to give high output. When the nonvalent zinc exceeds 60%, the aspect ratio becomes high to give high output, but the medium noise increases to degrade the SN ratio because of the relative decrease of bivalent zinc. By this method, the obtd. medium has high aspect ratio, high output and low noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a magnetic recording medium used in a magnetic disk device and the like, and more particularly to a magnetic recording medium suitable for high-density recording.

[Conventional technology and its problems]

Magnetic disk drives are used as external storage devices for computers because of their high storage capacity and high-speed access. Furthermore, coating-type media have conventionally been used as magnetic recording media used in magnetic disk devices.

However, in recent years, due to the trend toward higher capacities in magnetic disk drives, thin films of ferromagnetic metals made of iron, cobalt, nickel, or alloys thereof are formed by means such as electrolytic plating, electroless plating, vacuum evaporation, and sputtering. The method is attracting attention.

In particular, cobalt alloy magnetic films obtained by these methods have high reef holding power and high residual magnetic flux density, and are suitable for high-density recording. However, in order to achieve even higher recording density, it is necessary to satisfy the demands for higher output and lower noise.

An object of the present invention is to solve these technical problems and provide a magnetic recording medium with a high squareness ratio, high output, and low noise.

[Means to solve the problem]

The present inventors conducted various studies on the composition of the magnetic film in order to achieve the above object, and found that when zinc is contained in the magnetic film, the presence state (valence) of zinc in the magnetic film can be adjusted. It was discovered that the output can be high and the noise can be low while keeping the squareness ratio high.The present invention has been made based on these findings.

That is, the present invention provides a magnetic recording medium having a magnetic film containing cobalt as a main component and zinc on a substrate, in which the ratio of zero-valent zinc to divalent zinc in the magnetic film is 40 to 60:
This is a magnetic recording medium characterized by being 6O-1IO.

The magnetic recording medium of the present invention will be explained in detail below.

The substrate used in the present invention is made of an inorganic or organic nonmagnetic material. Specific examples of inorganic substances include:
Non-magnetic metals or alloys such as aluminum, aluminum alloys, copper, and silicon may be used, and ceramics such as glass, alumina, and silica may also be used. Examples of organic substances include ABS resin, polycarbonate resin,
Examples include synthetic resins such as polyester resins.

A nonmagnetic nickel/phosphorus layer may be provided on the surface of the substrate as an underlayer, for example, by electroless plating.

After mirror-polishing the substrate or base layer and, if necessary, performing texturing treatment (creating fine, uniform grooves in the form of concentric circles on the surface).

A magnetic layer containing cobalt as a main component and zinc is formed by electroless plating, vacuum evaporation, sputtering, or the like.

For example, in the case of electroless plating, the above substrate or the substrate provided with the underlayer is immersed in an electroless plating bath for 30 to 30 minutes.
Plating treatment is performed at a temperature of 90°C.

In the electroless plating bath, cobalt ions, zinc ions,
Contains complexing agents, reducing agents, pH adjusters, metal ions such as nickel ions, manganese ions, and tungsten ions, and buffering agents.

Cobalt ions are supplied by dissolving cobalt sulfate, sulfaminates, nitrates, halogen compounds, acetates, etc. in an electroless plating bath, and the concentration is usually 0.00/~0. ! ; mol/E, preferably 0. It is in the range of o o s-0.2 mol/l.

Zinc ions are supplied by dissolving zinc sulfates, nitrates, halogen compounds, etc. in an electroless plating bath. Zinc ion concentration is usually 0.000/~0.2m
ol/l, more preferably 0. o o
o y −o, θ! It is in the range of r mol/l.

o, oooo At concentrations lower than 1 mol/l, there is no effect of high output and low noise; A concentration higher than comol/l is not preferable because it causes a decrease in the reactivity of the plating solution and a significant deterioration in magnetic properties (decreased coercive force, decreased squareness, etc.).

In addition, metal ions such as nickel ions are supplied by dissolving sulfates, nitrates, halides, acetates, etc. of metals such as nickel in an electroless plating bath, and the concentration of metal ions such as nickel ions is usually 0.0OO/~0
．． 3m01/l, more preferably aθθ/
~o,/mol/l.

Complexing agents include carboxyl groups, amino groups,
A compound having a hydroxyl group is used.

As specific examples, oxycarboxylic acids such as tartaric acid, citric acid, and malic acid, or aminocarboxylic acids such as glycine, DL-α-alanine, glutamic acid, and aspartic acid are suitable, and other dicarboxylic acids such as malonic acid and succinic acid are also suitable. good. Usually, these complexing agents are used in combination, but
The concentration is preferably in the range of 0.0/- Omol/l.

As the reducing agent, dimethylaminoborane, a borohydride compound, and a hydrazine salt monopolyphosphite are used, but sodium hypophosphite is preferable from the viewpoint of stability of the plating solution, and its concentration is 0.00! r ~2.0 m0L/l is preferred.

As a pH adjuster, alkalis such as ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, etc. are used to increase the pH.
Acids such as sulfuric acid and hydrochloric acid are used to lower the pH. The pH of the plating solution is preferably in the range of 5 to 70.0. p
When H is lower than t and S, the zinc content in the magnetic film decreases and the proportion of zero-valent zinc tends to become too large. This is not very desirable since the ratio tends to be too high.

Ammonium salts, carbonates, borates, phosphates, organic acid salts, etc. are used as buffering agents, and the concentration thereof is 0. Oj−λ,
A range of o mol/l is preferred.

A magnetic film containing fupart as a main component and containing zinc is formed on a substrate using a plating bath having the composition and plating conditions as described above. Furthermore, as a protective film, a silicon dioxide film using a spin code method, a carbon film using a sputtering method, etc. may be formed.

In the magnetic recording medium of the present invention, the ratio of zero-valent zinc to divalent zinc in the magnetic film is 'IOS-60z
6θ~po, preferably lI5~3;! ;:! ;!
-'I! It is characterized by being r. If the proportion of zero-valent zinc in the magnetic film is less than aO%, the squareness ratio of the magnetic recording medium will be low and high output will not be obtained. On the other hand, if the proportion of zero-valent zinc in the magnetic film is more than 60%, the squareness ratio of the magnetic recording medium will be high (and high output will result, but the proportion of covalent zinc will be relatively low), Media noise increases and the S/N ratio deteriorates.

Furthermore, the zinc content in the magnetic film is usually 0.5% by weight.
The preferred range is /~J weight t%.

In addition, it is preferable to contain nickel, phosphorus, etc. in the magnetic film, and it is particularly preferable to contain nickel in an amount of 5 to 3θ weight f% and phosphorus in an amount of 41 to 6 weight %.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the examples unless it goes beyond the gist thereof.

Example/A 25 μm thick nickel-phosphorus magnetic material was formed on an aluminum substrate for a magnetic disk with a diameter of 3.5 inches by electroless plating. The surface was mirror-polished using a polishing machine and textured after cleaning. Next, a degreasing treatment was performed at 75° C. for 3 minutes, and an activation treatment was further performed.

(Hydrogenate to plating solution sl with the composition shown in Table 2) IJ
pH was adjusted to 9. Adjust the temperature to ℃
I made it. The substrate after the activation treatment is immersed in this plating solution, and the film thickness is 0. A magnetic film with a thickness of θj μm was formed. A carbon film having a thickness of eooA was formed on this magnetic film by sputtering.

The magnetic properties, electromagnetic conversion properties, magnetic film composition, and state of existence (valence) of zinc in the magnetic film were investigated for the magnetic recording medium thus obtained.

The magnetic properties were measured using a vibrating sample magnetometer under the conditions of an external magnetic field of S kilo Oersted.

The bending force was measured using a head for track density /θ and 0TPI /F frequency /, 25 MHz, 2F frequency j, JJ
MHz, relative speed9. The test was carried out under the condition of g m/sec.

Noise was measured using a spectrum analyzer.

Analysis of the state of zinc in the magnetic film was performed using X manufactured by KRATO8.
The measurement was carried out using a line photoelectron spectrometer (XSAMgθθ) under the following measurement conditions.

■ Measurement conditions Vacuum degree s x t o-8 Torr Excitation XII! Source AIKα (/4tKV x 20
mA) X-ray energy /da gb, beV Spectral mode FRR=F 1xed Retardi
ngRatio (Retarding Rati.

=53) Analysis area Hi-magnification=311
×lI'll1IL Resolution Hi-resolution scanning Width Narrow scanning 20 eV Automatically measured by computer (DEC PDP//10.L) Ar+etch Ar gas pressure /X/θ-'Torr
Conditions Acceleration chamber FE, 7.5e. , Etching speed approx. A/min ■ Determining the amount ratio of ZnO and Zn'' After performing Ar + etching for about 30 seconds to remove dirt on the sample surface, Znt and MM domain spectra were measured (energy is kinetic energy (K, F,
)display).

Measurement width? ? ? eVS-999eV (20eV width) baseline correction Connect approximately 9 g/eV and approximately 99 g eV with a straight line.

The peak heights of ZnO and Zn2+ were read and the amount ratio was determined.

(Zn'?9gg, around g eV, Zn'?9gg,?eV
Table 1 shows the analysis results of the magnetic film at around eV.

The zinc content in the magnetic film was 1% by weight.

The ratio of zero-valent zinc to covalent zinc in the magnetic film is so:
It was so. The obtained magnetic recording medium has a high squareness ratio (,
It has high output and low noise, and can be practically used as a high-density magnetic recording medium.

Example A magnetic recording medium was manufactured under the same conditions and operations as in Example 1, except that the composition of the plating solution and the plating conditions were changed as shown in Table 1.

The results are shown in Table 1.

Example 3 A magnetic recording medium was manufactured under the same conditions and operations as in Example 1, except that the composition of the plating solution and the plating conditions were changed as shown in Table 2.

The results are shown in Table 1.

Example A magnetic recording medium was manufactured under the same conditions and operations as in Example 1, except that the composition and conditions of the Hiroshi plating solution were changed as shown in Table 2.

The results are shown in Table 7.

Comparative Example A magnetic recording medium was manufactured in the same manner as in Example except that the composition of the plating solution and the plating conditions were changed as shown in Table 2.

The results are shown in Table 7. The obtained magnetic recording medium has poor output resolution balance and is unsuitable for high-density recording.

Comparative Example A magnetic recording medium was manufactured in the same manner as in Example except that the composition of the plating solution and the plating conditions were changed as shown in Table 2.

The results are shown in Table 1. The obtained magnetic recording medium has poor output resolution balance and is unsuitable for high-density recording.

Comparative Example 3 A magnetic recording medium was manufactured in the same manner as in Example except that the composition of the plating solution and the plating conditions were changed as shown in Table 2.

The results are shown in Table 1. The obtained magnetic recording medium has high noise<poor signal-to-noise ratio, and is therefore unsuitable for high-density recording.

Comparative Example A magnetic recording medium was manufactured in the same manner as in Example except that the composition of the plating solution and the plating conditions were changed as shown in Table 2.

The results are shown in Table 1. The resulting magnetic recording medium has a poor squareness ratio and cannot provide high output, making it unsuitable for high-density recording.

〔Effect of the invention〕

According to the present invention, a magnetic recording medium suitable for high-density recording with a high squareness ratio (high output force and low noise) can be obtained, and is therefore industrially useful.

Claims (1)

[Claims] (1) In a magnetic recording medium having a magnetic film containing cobalt as a main component and zinc on a substrate, the ratio of zero-valent zinc to divalent zinc in the magnetic film is 40-60:60-40. A magnetic recording medium characterized by: