JPH0547556A - Semi-hard magnetic film and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an electroless plating method of stably manufacturing an isotropic semi-hard magnetic film so as to replace a semi-hard magnetic film large in saturation magnetization, possessed of a coercive force of 30-300Oe and suitable for a base layer used in a vertical recording medium but having such a problem that magnetic anisotropy occurs causing coercive force to vary. CONSTITUTION:An in-plane magnetic isotropic thin film at least composed of Co, Mn, and B as component elements is provided. The film is formed through an electroless plating bath which is obtained by adding citric acid groups or malic acid groups as complexing agent to an aqueous solution which contains cobalt ions and manganese ions as metal ions and dimethylamine volan or diethylamine volan as reducing agent for the metal ions concerned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-hard magnetic film used as an underlayer of a magnetic recording medium applied to perpendicular recording and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a magnetic recording device such as a general magnetic disk device or a magnetic tape device, recording has been performed by magnetizing in the longitudinal direction of a magnetic recording medium.
In this method, there is a drawback that the demagnetizing field in the medium increases with the increase of the recording density, the residual magnetization is attenuated and rotated, and the reproduction output is significantly reduced. Therefore, the demagnetizing field becomes smaller as the recording density increases, and a perpendicular recording method that enables high-density recording and a CoCr sputtered film that is easy to magnetize in the direction perpendicular to the film thickness are proposed as a magnetic recording medium suitable for this perpendicular recording. (Japanese Patent Application Laid-Open No. 52-134706). In order to efficiently perform such perpendicular recording, a magnetic recording body having a two-layer magnetic film has been proposed (Japanese Patent Publication No. 58-91). The two-layer magnetic film is composed of a perpendicular magnetic recording layer (magnetic recording medium) and an underlayer having a low coercive force. This underlayer acts to cancel the magnetic pole on the back surface of the perpendicular magnetic recording layer, and thus the demagnetization effect is reduced. It is possible to increase the reproduction output. The underlayer of the two-layer magnetic film is mainly composed of a FeNi film (permalloy) formed by a sputtering method and MoFeN.
i film (molybdenum permalloy), CoZr film, CoZr
A soft magnetic film such as an Nb film is used. However, when a soft magnetic film is used as an underlayer of the perpendicular magnetic recording layer (magnetic recording medium), the reproduction output is improved, but the domain wall movement is likely to occur due to the low coercive force, and noise is likely to occur. For this reason, it has been proposed to use a semi-hard magnetic film of cobalt or cobalt-nickel alloy instead of the soft magnetic film (JP-A-2-18710). If the coercive force of this semi-hard magnetic film is smaller than 30 Oe, it causes spike noise, and if it is larger than 300 Oe, recording on the underlayer becomes difficult (because the action of canceling the magnetic pole on the back surface is reduced). It is said that it is preferably in the range of to 300 Oe.

[0003]

Such a base layer is
It is produced by a dry film forming method such as sputtering, vapor deposition, and ion plating. In this case, there is a problem in mass productivity because it is performed in a vacuum system. Therefore, application of an underlayer formed by an electroless plating method that is excellent in mass productivity by improving manufacturing problems is being studied. This includes electroless N
iFeP plated film, electroless NiP plated film, electroless Ni
The WP plating film and the like are applied, but the largest reproduction output can be obtained when the NiFeP film having a relatively large saturation magnetization of 400 emu / cc is used.
IEEE Transaction on Magnetics No. Mag-
23, pp. 2356-2358, 1987). The saturation magnetization is 1400 emu / c in the electroless plating method.
Co of about c (value about 3.5 times that of NiFeP film) and large Co
The B film can be produced, and the effect of increasing the output is expected. As the electroless CoB plating bath, there is a caustic alkaline plating bath using tartaric acid as a complexing agent (Abstracts of Scientific Lectures of the Japan Society for Applied Magnetics, p. 483, 1989). But,
The soft magnetic film or the semi-hard magnetic film of a Co alloy has a problem that the magnetic properties are generally liable to be illegal. The MH loop magnetically measured in a certain direction in the film plane has a shape close to a rectangle (easy magnetization direction), but when measured in the direction orthogonal to the MH loop, the squareness is poor and the coercive force is reduced. This is the phenomenon of being magnetized (hard magnetization direction). In addition, depending on the measurement direction, there may be an intermediate state, but in any case, if the magnetic characteristics are anisotropic,
There is an easy magnetization direction and a difficult magnetization direction somewhere. If the easy magnetization direction does not match the recording / reproducing direction, it becomes a factor that changes the recording / reproducing characteristics. It is possible to apply a magnetic field during plating to control the anisotropy, but it is difficult to apply a constant magnetic field in the circumferential direction in a shape like a magnetic disk. Further, in the case of mass production by electroless plating, it becomes more difficult to apply a magnetic field. The object of the present invention is to improve the conventional problems and to form a Co-based alloy having a coercive force of 30 to 300 Oe and a large saturation magnetization,
An object of the present invention is to provide an isotropic semi-hard magnetic film having almost no anisotropy in magnetic properties, and a method for producing a semi-hard magnetic film using an electroless plating method for stably producing the same. ..

[0004]

The present invention is an in-plane magnetic anisotropy thin film containing at least Co, Mn and B as constituents and having a coercive force in the in-plane direction of 30 to 300 O.
It is a semi-hard magnetic film characterized by being e. Further, the method for producing a semi-hard magnetic film of the present invention contains cobalt ions and manganese ions as metal ions,
By using an aqueous solution containing dimethylamine borane or diethylamine borane as a reducing agent for the metal ions and containing at least a citric acid group and a malic acid group as a complexing agent for the metal ions as an additive, an electroless plating method is used. It is characterized by forming. The Mn content of the semi-hard magnetic film of the present invention is in the range of 0.02 to 10% by weight, preferably 0.1 to 10% by weight. The effect begins to appear when the Mn content is 0.02% by weight. For example, when the fluctuation of the coercive force on the same circumference of the magnetic disk is examined, the fluctuation is ±
It can be suppressed to 20%, but when it is 0.1% by weight or more, the fluctuation of the coercive force is significantly within ± 7%. It is difficult to set the Mn content to 10 wt% or more by electroless plating, and the saturation magnetization is also reduced to 1000 emu / cc or less. The main components of the electroless plating bath used in the present invention include cobalt ions and manganese ions as metal ions, dimethylamine borane or diethylamine borane as a reducing agent for the metal ions, and a citric acid group as a complexing agent for the metal ions. And contains a malic acid group,
Additives such as a pH buffering agent, a brightening agent, a smoothing agent, a stimulant, an anti-pinhole agent, and a surfactant can be further used as long as the objects and effects of the present invention are not impaired.

Cobalt ions are supplied by dissolving a soluble salt of cobalt sulfate, chloride or acetate in an electroless plating bath. The cobalt ion concentration is in the range of 0.005 to 0.5 mol / l, preferably 0.01 to 0.3 mol / l. Manganese ions are supplied by dissolving soluble salts such as manganese sulfate, chloride, and acetate in an electroless plating bath. Manganese ion concentration is 0.0
A range of 01 to 0.4 mol / l is used, but a range of 0.005 to 0.2 mol / l is preferable. The metal ions used in the present invention are mainly composed of cobalt and manganese, but a small amount of Ni, Fe,
Be, Mg, Al, Ru, Si, Sr, Y, Zn, Z
r, Nb, Cd, In, Sb, Ta, Ir, Hg, T
l, Nb, Gd, Tb, Ti, V, Cr, Cu, Ga,
Ge, W, Mo, Rh, Pd, Ag, Au, Pt, S
n, Te, Ba, Ce, Sm, Os, Pb, Re, Bi
And other ions may be contained within a range that does not impair the effects of the present invention. As the reducing agent, dimethylamine borane or diethylamine borane or derivatives thereof,
0.0001 to 0.3 mol / l, preferably 0.00
It is used in the range of 5 to 0.1 mol / l.

The citric acid group as a complexing agent is supplied by citric acid or a soluble salt of sodium citrate, potassium citrate or the like. These are 0.001 to 0.
Used in the range of 8 mol / l, but 0.01 to 0.2
A range of 5 mol / l is preferred. The malic acid group as a complexing agent is supplied by malic acid or a soluble salt such as sodium malate, potassium malate and the like. These are used in the range of 0.001 to 2 mol / l,
The range of 0.05 to 1.1 mol / l is preferable. Other complexing agents include formic acid, acetic acid, propionic acid,
Butyric acid, isobutyric acid, valeric acid, isovaleric acid, oxalic acid, glutaric acid, maleic acid, tartaric acid, fumaric acid, citraconic acid, itaconic acid, tricarballylic acid, succinic acid, malonic acid, glycolic acid, thioglycol Acid, lactic acid, β-hydroxypropionic acid, pyruvic acid, oxalacetic acid, diglycolic acid, thiodiglycolic acid, mercaptosuccinic acid, dimercaptosuccinic acid, benzoic acid, mandelic acid, phthalic acid, salicylic acid, ascorbic acid, sulfo Carboxylic acids such as salicylic acid, tropolone, 3-methyltropolone and Tyrone, amines such as ethylenediamine, diethylenetriamine, triethylenetetraamine and pyridine and their derivatives, iminodiacetic acid, iminodipropionic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminediacetic acid ， D Diamine tetraacetic acid,
Aminopolycarboxylic acids such as ethylenediaminetetrapropionic acid and diethylenetriaminepentaacetic acid, alanine, sarcosine, valine, norleucine, tyrosine, cysteine, glutamic acid, glycine, aspartic acid,
Amino acids such as asparagine and histidine, gluconic acid,
Hexonic acids such as allonic acid, idonic acid, galactonic acid, gulonic acid, taronic acid, and mannonic acid, weak acids such as pyrophosphoric acid, and one or more combinations of soluble salts thereof within the range that does not impair the effects of the present invention. May be used in.

As the pH buffer, ammonium sulfate,
Ammonium salts such as ammonium chloride and boric acid are used. The concentration range is 0.001 to 2 mol / l, preferably 0.03 to 0.7 mol / l. p
As the H-adjusting agent, ammonia or a hydroxide such as NaOH, LiOH, KOH as caustic is used alone or in combination of two or more. It is also possible to use ammonia and caustic together. Usually p
The plating solution without H-regulator before the bath is in the neutral or acidic range.
Adjusted. When the pH exceeds the required level, acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid are used for pH reduction. The pH range used is between 4 and 13, preferably between 7 and 11.

[0008]

[Function] The center of the electroless plated film is Co particles.
It is considered that the element becomes rich, and the mixed elements such as B and P are distributed to the outside to form a layer close to non-magnetic and have a structure that encloses the Co-rich portion. In an electroless plated CoP alloy film, about 2 to 5% of P can be co-deposited, so such a non-magnetic layer becomes thicker, magnetic isolation of Co particles progresses, and high protection of several hundred Oe or more is achieved. A hard magnetic film having a magnetic force can be obtained. Further, the magnetic anisotropy tends to be isotropic in the plane. On the other hand, in the electroless plated CoB alloy film, the amount of eutectoid B is usually as small as 1% or less, which is close to pure Co
Since it becomes an oB alloy film, a soft magnetic film of about several Oe or less is likely to be obtained. In the case of a soft magnetic film close to pure Co, the crystal magnetic anisotropy and the strain magnetic anisotropy are easily influenced by the geomagnetism during the film formation, and also due to a local slight difference in composition and stress. It is thought that it tends to occur in a certain direction. For this reason, the inventors have extensively studied experimentally to obtain an isotropic film structure by adding a third element to the CoB alloy film so that anisotropy is not caused by a slight factor. It became clear that the addition was effective. It was also found that by using citric acid groups and malic acid groups as complexing agents in the electroless CoMnB plating bath, a semi-hard magnetic film having a large saturation magnetization can be stably obtained and can be applied to the object of the present invention. The present invention has been brought about by obtaining such knowledge.

[0009]

EXAMPLES Next, examples of the present invention will be described. Example 1 A non-magnetic NiP was formed on an aluminum alloy disc having a diameter of 8.25 inches.
The layer was plated and the surface was mirror-polished to give a disk substrate. On this substrate, a CoMnB film having a film thickness of 0.05 μm was formed using the electroless plating bath described below. Electroless plating bath (1) Bath composition Cobalt sulfate 0.10 mol / l Manganese sulfate 0-0.11 mol / l Dimethylamine borane 0.015 mol / l Ammonium sulfate 0.1 mol / l Sodium malate 0.4 mol / l Sodium citrate 0.04 mol / l Plating conditions Bath temperature 70 ° C. pH of plating bath 8.0 (pH adjustment with ammonia at room temperature) Disk substrate radius 80-90 mm, diameter 10 m
It was cut into m and used as a measurement sample. The results of measuring the magnetic characteristics of the CoB film or the CoMnB film obtained by changing the manganese sulfate concentration using a vibrating sample magnetometer are shown in FIG.
The direction in which the coercive force was maximized was measured by changing the direction in the film plane, and the direction in which the coercive force was maximum was the easy magnetization direction. The coercive force Hc was 65 Oe when manganese sulfate was not added. Hc can be increased by the addition of manganese sulfate concentration,
It became 90 Oe at 05 mol / l.

Next, at a radius of 80 to 90 mm of the disk substrate, a measurement sample having a diameter of 10 mm was cut out every 30 degrees, and the coercive force was measured in the circumferential direction. Manganese sulfate 0mo
1 / l, 0.005 mol / l and 0.05 mol /
The result of coercive force measurement in the case of 1 is shown in FIG. In the case of manganese sulfate of 0 mol / l, the magnetization was almost in the easy direction and the coercive force was 65 Oe at the angle of 0 degree, but the coercive force was 25 Oe in the difficult direction at the angle of 120 degree. Anisotropy is generated in the magnetic properties, and the fluctuation of the coercive force on the same circumference reaches ± 45%. Manganese sulfate 0.00
In the case of 5 mol / l, the coercive force was in the range of 66 to 73 Oe, and the fluctuation of the coercive force on the same circumference was reduced to ± 5%.
The fluctuation of the coercive force decreased with the increase of the manganese sulfate concentration, and when the manganese sulfate was 0.05 mol / l, the fluctuation of the coercive force on the same circumference decreased to ± 2%. Even when the manganese sulfate concentration was further increased, the fluctuation of the coercive force was suppressed to ± 2%, but when it exceeded 0.11 mol / l, plating deposition became gradually difficult. Manganese sulfate 0.005 mol /
In the case of 1, the Mn content in the film was 0.1% by weight, and the saturation magnetization showed a large value of 1370 emu / cc. The Mn content in the film increases with the manganese sulfate concentration, and the saturation magnetization decreases, but 0.005 to 0.11 mol / l
The saturation magnetization of the CoMnB film obtained in the concentration range of 100 is 100.
It showed a large value of 0 emu / cc or more. Also, 0.0
The plating bath was stable in the concentration range of 05 to 0.11 mol / l.

Example 2 A CoMnB film having a film thickness of 0.1 μm was formed in the same manner as in Example 1, but the following electroless plating bath was used in this example. Electroless plating bath (2) Bath composition Cobalt sulfate 0.05 mol / l Manganese sulfate 0-0.1 mol / l Dimethylamine borane 0.01 mol / l Ammonium sulfate 0.1 mol / l Sodium malate 0.5 mol / l Sodium citrate 0.18 mol / l Plating condition Bath temperature 70 ° C. pH of plating bath 9.0 (pH adjusted with ammonia at room temperature) CoB film or Co obtained by changing manganese sulfate concentration
The magnetic characteristics of the MnB film were measured in the same manner as in Example 1.
Regarding the coercive force in the easy magnetization direction, it was 15 Oe when manganese sulfate was not added, but Hc can be increased by adding manganese sulfate concentration.
It became 30 Oe at mol / l. When the manganese sulfate concentration further increased, Hc increased, reaching a maximum value of 65 Oe at 0.04 mol / l, then slightly decreasing, and 6 at 0.1 mol / l.
It becomes 0 Oe. Regarding the fluctuation of coercive force on the same circumference,
When the content of manganese sulfate was 0 mol / l, it reached ± 55%, but it decreased to ± 7% at 0.005 mol / l manganese sulfate, and to ± 3.5% at 0.04 mol / l manganese sulfate. When the manganese sulfate concentration was further increased, the fluctuation of the coercive force was suppressed to within ± 3.5%, but 0.1 mol
If it exceeds / l, plating deposition becomes gradually difficult. When manganese sulfate was 0.005 mol / l, the Mn content in the film was 0.1% by weight, and the saturation magnetization was 1380 emu / l.
It showed a large value of cc. Although the Mn content in the film increased with the manganese sulfate concentration and the saturation magnetization decreased,
CoMn obtained in the concentration range of 05 to 0.1 mol / l
The saturation magnetization of the B film showed a large value of 1000 emu / cc or more. The plating bath was stable in the concentration range of 0.005 to 0.1 mol / l.

Example 3 A CoMnB film having a film thickness of 0.1 μm was formed in the same manner as in Example 1, but the following electroless plating bath was used in this example. Electroless plating bath (3) Bath composition Cobalt chloride 0.15 mol / l Manganese sulfate 0-0.25 mol / l Dimethylamine borane 0.02 mol / l Ammonium sulfate 0.25 mol / l Sodium malate 0.4 mol / l Sodium citrate 0.35 mol / l Plating condition Bath temperature 70 ° C. pH of plating bath 10.0 (pH adjusted with ammonia at room temperature) CoB film or Co obtained by changing manganese sulfate concentration
The magnetic characteristics of the MnB film were measured in the same manner as in Example 1.
The coercive force in the easy magnetization direction was 195 Oe when manganese sulfate was not added, but Hc can be increased by adding manganese sulfate concentration.
It became 230 Oe at mol / l. When the manganese sulfate concentration further increases, Hc increases, reaches a maximum value of 295 Oe at 0.14 mol / l, and then decreases, and reaches 250 Oe at 0.25 mol / l. Regarding the fluctuation of the coercive force on the same circumference, it reached ± 50% when manganese sulfate was 0 mol / l, but decreased to ± 6% when manganese sulfate was 0.01 mol / l, and manganese sulfate was 0.14 mol / l. It decreased to ± 2.5%. Even when the manganese sulfate concentration was further increased, the fluctuation of the coercive force was suppressed to within ± 2.5%, but 0.25mo
When it exceeded 1 / l, plating precipitation became gradually difficult. When the manganese sulfate was 0.01 mol / l, the Mn content in the film was 0.12% by weight, and the saturation magnetization was 1360 emu.
It showed a large value of / cc. Although the Mn content in the film increased and the saturation magnetization decreased with the manganese sulfate concentration,
CoM obtained in the concentration range of 01 to 0.25 mol / l
The saturation magnetization of the nB film showed a large value of 1000 emu / cc or more. Further, the plating bath was stable in the concentration range of 0.01 to 0.25 mol / l.

Example 4 A CoMnB film having a film thickness of 0.1 μm was formed in the same manner as in Example 1, but the following electroless plating bath was used in this example. Electroless plating bath (4) Bath composition Cobalt sulfate 0.09 mol / l Manganese sulfate 0-0.15 mol / l Diethylamine borane 0.016 mol / l Ammonium sulfate 0.3 mol / l Sodium malate 0.35 mol / l Sodium citrate 0.05 mol / l Plating conditions Bath temperature 75 ° C. pH of plating bath 8.5 (pH adjusted with ammonia at room temperature) CoB film or Co obtained by changing manganese sulfate concentration
The magnetic characteristics of the MnB film were measured in the same manner as in Example 1.
Regarding the coercive force in the easy magnetization direction, it was 55 Oe when manganese sulfate was not added, but Hc can be increased by adding manganese sulfate concentration.
It became 85 Oe at ol / l. When the manganese sulfate concentration further increases, Hc increases, and the maximum value is 1 at 0.06 mol / l.
Decrease after reaching 05 Oe, 95 at 0.15 mol / l
Oe. The variation of coercive force on the same circumference reached ± 40% when manganese sulfate was 0 mol / l,
It decreased to ± 5.5% at 0.01 mol / l of manganese sulfate, and decreased to ± 2.5% at 0.06 mol / l of manganese sulfate. When the manganese sulfate concentration was further increased, the fluctuation of the coercive force was suppressed to within ± 2.5%, but 0.15mo
When it exceeded 1 / l, plating precipitation became gradually difficult. When manganese sulfate was 0.01 mol / l, the Mn content in the film was 0.1% by weight, and the saturation magnetization was 1365 emu / l.
It showed a large value of cc. Although the Mn content in the film increased with the manganese sulfate concentration and the saturation magnetization decreased,
CoMn obtained in the concentration range of 1 to 0.15 mol / l
The saturation magnetization of the B film showed a large value of 1000 emu / cc or more. The plating bath was stable in the concentration range of 0.01 to 0.15 mol / l.

In each of Examples 1 to 4, a substrate obtained by plating a non-magnetic NiP layer on an aluminum alloy plate was used. However, an electroless Cu plating layer, an electrolytic Cu plating layer, an electroless NiCu layer is used.
P plating layer, electroless NiSnP plating layer, electroless Ni
Also when using a substrate on which a plating layer other than NiP such as a WP plating layer or an electroless NiWP plating layer is formed, or a substrate such as a copper substrate, a brass substrate, a plastic subjected to an appropriate catalyst treatment, or a non-metal substrate such as glass. Similarly, the characteristics of an isotropic semi-hard magnetic film in which the anisotropy of magnetic characteristics was suppressed were obtained. Further, the film thickness of the CoMnB plating film is 0.0 in the embodiment.
Not limited to 5 and 0.1 μm, 0.00
It was possible to obtain the characteristics of an isotropic semi-hard magnetic film in which the anisotropy of magnetic characteristics was suppressed in the range of 5 to 10 μm.

[0015]

As described above, the C according to the present invention is as described above.
The coercive force of the oMnB semi-hard magnetic film is 30 to 300 O.
Since it is an isotropic film having a large saturation magnetization of 1000 emu / cc or more at e and suppressing anisotropy of magnetic characteristics, it is optimal as an underlayer film for a perpendicular magnetic recording layer and industrially useful. .. Further, this semi-hard magnetic film can be stably manufactured by the electroless plating method and is excellent in mass productivity.

[Brief description of drawings]

FIG. 1 is a diagram showing variations in coercive force of CoMnB semi-hard magnetic films obtained from plating baths having manganese sulfate concentrations of 0, 0.005 and 0.05 mol / l on the same circumference in one example of the present invention. ..

FIG. 2 is a diagram showing the relationship between the coercive force of the CoMnB semi-hard magnetic film obtained in one example of the present invention and the manganese sulfate concentration in the plating bath.

Claims (2)

[Claims] 1. A semi-hard magnetic film, which is an in-plane magnetic anisotropic thin film containing at least Co, Mn and B as constituent components and has a coercive force in the in-plane direction of 30 to 300 Oe. 2. A cobalt ion and a manganese ion as metal ions, dimethylamine borane or diethylamine borane as a reducing agent for the metal ions, and a citric acid group as a complexing agent for at least the metal ions as an additive. And a method for producing a semi-hard magnetic film, which is formed by an electroless plating method using an aqueous solution containing a malic acid group.