JPH0451882B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to magnetic recording media such as magnetic disks, magnetic drums, and magnetic tapes. [Prior Art and Problems] Conventionally, magnetic recording media are known to be obtained by coating a substrate with a magnetic material such as a metal oxide or alloy dispersed in an organic binder. However, in order to improve the recording density, methods of forming thin films of ferromagnetic metals made of iron, cobalt, nickel, or alloys thereof using methods such as electrolytic plating, electroless plating, vacuum evaporation, and sputtering have attracted attention. ing. In particular, cobalt alloy magnetic media obtained by these methods have high coercive force and high residual magnetic flux density, and are suitable for high-density recording. However, in order to achieve even higher recording density, the first step is to increase the coercive squareness ratio (hereinafter referred to as S*), and the second step is to increase the coercive squareness ratio (hereinafter referred to as S ^* ).
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 high S ^* , high output, and low noise, and a manufacturing method that can stably mass-produce this magnetic recording medium. [Means for Solving the Problems] In order to achieve the above object, the present inventors conducted various studies on the composition of the magnetic material, and found that it was selected from the group of cobalt, phosphorus, arsenic, antimony, and bismuth. By using a magnetic material made of an alloy containing one or more of the above-mentioned elements, S ^* was improved, and by using a magnetic material containing zinc in addition to the above-mentioned elements, S ^* was maintained high. We have found that the output is higher and the noise is lower. In addition, as a manufacturing method, electroless plating using dicarboxylic acid or oxycarboxylic acid as a complexing agent is the most stable method in terms of homogeneity, mass production, and economic efficiency of the magnetic film, and is the most stable method for mass production of high quality magnetic films. I found out that there is a way to do it. The present invention has been made based on these findings. That is, the first aspect of the present invention is a magnetic recording medium characterized in that a magnetic material made of an alloy containing cobalt, phosphorus, and one or more elements selected from the group of arsenic, antimony, and bismuth is provided on a substrate. A second aspect of the present invention is a magnetic recording characterized in that a magnetic material made of an alloy containing one or more elements selected from the group of cobalt, phosphorus, zinc, arsenic, antimony, and bismuth is provided on a substrate. The third aspect of the present invention is an alloy containing cobalt, phosphorus and one or more elements selected from the group of arsenic, antimony and bismuth, or a medium selected from the group of cobalt, phosphorus, zinc and arsenic, antimony and bismuth. This method of manufacturing a magnetic recording medium is characterized in that a magnetic body made of an alloy containing one or more elements is formed by electroless plating using dicarboxylic acid as a complexing agent. The magnetic recording medium and method for manufacturing the same according to 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 aluminum, aluminum alloys,
Non-magnetic metals or alloys such as copper and silicon may be used, and ceramics such as glass, alumina, and silica may also be used. ABS as an organic material
Synthetic resins such as resin, polycarbonate resin, and polyester resin. A base layer may be provided on the surface of the substrate. The underlayer is, for example, a nonmagnetic nickel phosphorus layer formed by electroless plating. After mirror-polishing the substrate or underlayer and, if necessary, performing a texturing treatment (creating concentric fine, uniform grooves on the surface), the magnetic material is provided. The magnetic material is an alloy containing cobalt, phosphorus, and one or more elements selected from the group of arsenic, antimony, and bismuth, or an alloy containing zinc in addition to the above-mentioned elements, and the saturation magnetic flux density is adjusted. You may also add nickel to these. Among the group of arsenic, antimony and bismuth which are part of the alloy components of the magnetic material, arsenic and bismuth are particularly preferred. The proportions of these elements are not particularly limited, but preferably cobalt is 70 to 95 at%, phosphorus is 5 to 20 at%, and one or more elements selected from the group of arsenic, antimony, and bismuth is 0.5 to 5 atoms. %, zinc is in trace amounts. Further, when nickel is added for the above-mentioned purpose, the amount of nickel is preferably 5 to 20 at %. If the blending ratio of cobalt is less than 70 atomic %, the saturation magnetic flux density will decrease, resulting in a decrease in output. When sodium hypophosphite is used as a reducing agent in an electroless plating method, the blending ratio of phosphorus is necessarily 5 atomic % or more. If the amount of one or more elements selected from the group of arsenic, antimony, and bismuth is less than 0.5 atomic percent, S ^*
does not improve sufficiently. On the other hand, if it exceeds 5 atomic %, noise will increase. A trace amount of zinc is sufficient. The magnetic material is formed by electroless plating or the like. In the case of the electroless plating method, the composition of the electroless plating solution includes cobalt ions such as sulfate, nitrate, halogen compound, acetate, etc., and the concentration is usually 0.001 to 0.5 mol/, preferably 0.01 to
The range is 0.06 mol/. Suitable nickel ions include sulfates, nitrates, halides, acetates, etc., and the concentration of nickel ions used is usually in the range of 0.0002 to 0.3 mol/, more preferably 0.001 to 0.1 mol/. When one or more elements selected from the group of arsenic, antimony and bismuth is arsenic, arsenate and arsenite are suitable, and usually 7×10 ^-5 to 3×
It is used at a concentration of 10 ^-2 mol/, more preferably in the range of 1 x 10 ^-4 to 1.3 x 10 ^-2 mol/. When one or more elements selected from the group of arsenic, antimony, and bismuth is bismuth, sulfates, nitrates, halides, etc. are suitable, and the concentration is usually 1×10 ^-4 to 1×10 ^-2 mol/ It is preferably used in the range of 2×10 ^-4 to 5×10 ^-3 mol/
is within the range of If the concentration of elements belonging to group b of the periodic table is below the above, no improvement in S ^* can be expected.
If it exceeds this range, the reactivity of the plating solution decreases, which is not preferable. Suitable zinc ions include sulfates, nitrates, and halogen compounds. Zinc ion concentration is usually 2
The range is from ×10 ⁻⁶ to 0.02 mol/, more preferably from 0.5 to 10 ⁻³ to 5×10 ⁻³ mol/. Below this range, there is no effect of high output and low noise, and above this range, the reactivity of the plating solution decreases, which is not preferable. In the case of electroless plating, it is necessary to add a complexing agent, a buffering agent, a reducing agent, and a PH adjusting agent in addition to the above-mentioned ions. Compounds having a carboxyl group, an amino group, or a hydroxyl group in the molecule are known as complexing agents.
As specific examples thereof, amino acids such as α-alanine and serine, or dicarboxylic acids such as malonic acid and succinic acid are suitable, and oxycarboxylic acids such as gluconic acid, tartaric acid, mucic acid, and citric acid may also be used. Its concentration ranges from 0.01 to 2.0 mol/. Ammonium salts, carbonates, borates, phosphates, organic acid salts, etc. are used as buffering agents, and their concentrations are . It is in the range of 0.05 to 2.0 mol/. Reducing agents include dimethylaminoborane, borohydride compounds, hydrazine salts, sodium hypophosphite, etc. However, considering the stability of the plating solution, sodium hypophosphite should be added at 0.01 to 2.0 mol/min.
It is more desirable to use it within the range of . PH regulators include ammonia, sodium hydroxide,
Potassium hydroxide, sodium carbonate, etc. may be used. The pH of the plating solution is preferably in the range of 7.5 to 11.0. The temperature of the plating solution is usually preferably in the range of 55 to 90°C. A magnetic material is formed on a substrate using a plating solution having the composition and plating conditions as described above, and a protective film is formed thereon. As the protective film, a silica film formed by a spin coating method, a carbon film formed by a sputtering method, etc. are known. [Example] Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. Examples 1 to 12 Aluminum disks with a diameter of 90 mm, an inner diameter of 32 mm, and a thickness of 1.27 mm were manufactured by lathe processing. A 20 μm thick nickel-phosphorus underlayer was formed on this disk by electroless plating. This surface was polished to a mirror finish using a polishing machine, and the surface roughness (R _nax ) was 0.04 μm.
Finished. Then, fine concentric grooves were created using a texturing machine. The surface roughness (R _nax ) was maintained at 0.04 μm. The aluminum disk thus obtained (hereinafter referred to as the Ni.P substrate) was degreased by immersing it in a sodium hydroxide solution at a temperature of 40° C. and a concentration of 2 mol/min for 5 minutes. Sodium hydroxide was added to plating solution 10 having the composition shown in Table 1 to adjust the pH to 8.6 and the temperature to 75°C. A magnetic material having a film thickness of 0.08 μm was formed by immersing the disc after the degreasing treatment in this plating solution. A carbon film with a thickness of 500 Å was formed on this magnetic material by sputtering. S ^* , output and noise were measured for the aluminum disk thus obtained. S ^* was measured by taking a 7 mm x 14 mm sample piece and using a vibrating sample magnetometer under an external magnetic field of 10 kOersted. The output was measured using a head with a track density of 900 TPI, 1F frequency 1.25MHz, 2F frequency 2.5MHz,
The test was conducted at a relative speed of 9.6 m/sec. Noise measurements were performed using a spectrum analyzer. As a result, as shown in Table 1, it was found that S ^* , output, and noise were improved, and it could be practically used for high-density recording media. When the obtained magnetic material was analyzed by ESCA, 1 to 2 atomic % of arsenic or bismuth was detected as shown in Table 2. In addition, Examples 3, 4, 7
Traces of zinc were detected in samples 8, 11, and 12. From this result, S ^* , output, and noise are improved by containing one or more elements selected from the group of arsenic, antimony, and bismuth in the magnetic material, and in particular, by containing zinc in addition to the above elements. It is clear that the improvement effect becomes remarkable. Comparative Examples 1 and 2 An experiment was conducted in which one or more elements selected from the group of arsenic, antimony, and bismuth were not added to the plating solution. Conditions and operating method are as in Example 1~
A magnetic material was formed on an aluminum disk according to 8. The results are shown in Table 1, and the S ^* and output were lower and the noise was higher. Comparative Examples 3 to 5 A textured 3.5-inch N-P plated aluminum substrate prepared in the same manner as in the example was set in a batch-type DC magnetron sputtering machine and evacuated to 1×10 ^-7 Torr. Thereafter, the substrate was heated to 200° C., and a 500A Cr underlayer was formed in an Ar atmosphere of 2 mTorr. In the same apparatus, different Co alloy targets having different compositions were used to form magnetic layers of 800 Å and a constant power of 10 W/cm ² to obtain magnetic recording media having three types of compositions in Comparative Examples 3 to 5. Its magnetic properties were evaluated. The electromagnetic conversion characteristics were further evaluated by forming a 500 Å carbon film by sputtering and using the same method as for magnetic recording media made by plating. Table 1 shows the evaluation results.
As shown in Table 2, the S ^* and output were lower and the noise was higher. Example 9 Changes in S ^* , output, and noise depending on the concentration of zinc in the plating solution were investigated. Experiments were conducted for arsenic-added systems (experiments Nos. 1 to 6) and bismuth-added systems (experiments Nos. 7 to 12).
The other components of the plating solution were the same in each experiment: cobalt sulfate was 0.03 mol/mole, mucic acid was
0.2 mol/, boric acid 0.4 mol/ and sodium hypophosphite 0.3 mol/. As a result, as shown in Table 3, the zinc concentration increased in both the arsenic-added system and the bismuth-added system.
It was found that the goals of high output and low noise could be achieved at a concentration of 0.5×10 ^-3 mol/or higher. Example 10 The present inventors also conducted experiments on changes in coercive force depending on the concentration of a compound containing one or more elements selected from the group of arsenic, antimony, and bismuth in the plating solution. Only the concentration of the above compound in the plating solution was varied as shown in Table 4, and the other components were cobalt sulfate 0.03 mol/m and mucic acid.
0.2 mol/, boric acid 0.4 mol/, and sodium hypophosphite 0.3 mol/ were kept constant in each experiment.
The pH of the plating solution was adjusted to 8.6 by adding sodium hydroxide. As a result, as shown in Table 4, it was found that as the concentration of arsenic or bismuth increased, the coercive force decreased. For arsenic, 3×10 ^-3 mol/
In addition, in the case of bismuth, S ^* reached a high value of 0.90 or more at a concentration of 0.5×10 ^-3 mol/or more. These results revealed that coercive force can be controlled while maintaining a high S ^* value by adjusting the concentration of one or more elements selected from the group of arsenic, antimony, and bismuth in the plating solution.

【table】

[Table] Note 2 Comparative Examples 3 to 5 are those prepared by the sputtering method.

【table】

【table】

【table】

〔Effect of the invention〕

From the above results, it is clear that the following effects can be obtained by the present invention. That is, (1) cobalt;
By containing phosphorus and one or more elements selected from the group of arsenic, antimony, and bismuth, a magnetic recording medium with a high S ^* value, high output, and low noise can be obtained. (2) By simultaneously containing zinc and an element selected from the group of cobalt, phosphorus, arsenic, antimony, and bismuth, a high S ^* value can be maintained, and a high recording density with significantly improved output and noise can be achieved. A suitable medium is obtained.

Claims (1)

[Scope of Claims] 1. A magnetic recording medium characterized in that a magnetic material made of an alloy containing cobalt, phosphorus, and one or more elements selected from the group of arsenic, antimony, and bismuth is provided on a substrate. 2. A magnetic recording medium characterized in that a magnetic material made of an alloy containing one or more elements selected from the group of cobalt, phosphorus, zinc, arsenic, antimony and bismuth is provided on a substrate. 3 An alloy containing cobalt, phosphorus, and one or more elements selected from the group of arsenic, antimony, and bismuth, or cobalt, phosphorus, zinc, and
A magnetic material made of an alloy containing one or more elements selected from the group of arsenic, antimony and bismuth,
1. A method for producing a magnetic recording medium, characterized in that the magnetic recording medium is formed by electroless plating using dicarboxylic acid or oxycarboxylic acid as a complexing agent.