JP2001015339A - Soft magnetic laminate film and thin-film magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a soft magnetic thin film, which has high saturation magnetic flux density, high magnetic permeability in high-frequency regions, and superior heat resistance and a thin-film magnetic head which uses it. SOLUTION: This soft magnetic thin film is formed by alternately stacking a 1st ferromagnetic body layer 2 made of 1 kind or more among Fe, Co, and Ni and a 2nd ferromagnetic layer 3 made of alloy containing 1 kind or more among Fe, Co, and Ni, and N, the soft magnetic laminate film has a nonmagnetic layer 1 of Al, Si, Ti, Cr, Zr, Nb, Mo, Hf, Ta, or W and nitrides of the element between ferromagnetic body layers, and the thin-film magnetic head uses the soft magnetic laminate film for a write magnetic pole part or element shield part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a soft magnetic thin film material used for a core material or a shield of a magnetic head of a magnetic recording apparatus.

[0002]

2. Description of the Related Art A magnetic head used in a magnetic disk drive of a computer has a high density and a high speed of magnetic recording.
Along with miniaturization, those having a thin film structure are mainly used. By making the magnetic head a thin film structure, miniaturization,
Higher frequency of signals used, higher precision by thin film micromachining method,
Then, mass production and the like by simultaneously forming a large number on a substrate have become possible. In such a magnetic head, the soft magnetic material used for the write magnetic pole portion and the like is required to have high magnetic permeability, low coercive force, and high saturation magnetic flux density. In recent years, the trend toward higher density of magnetic signal recording and higher speed of writing / reading has been accompanied by more and more stringent demands for higher performance as well as higher performance.

Conventionally, a permalloy of an Fe-Ni alloy has been used as a magnetic material of the thin-film magnetic head.
The permalloy thin film is mainly formed by an electrodeposition method such as plating. In particular, permalloy of Ni ₈₂ Fe ₁₈ (subscript suffix is atomic%) has a magnetostriction constant of almost 0 and exhibits high magnetic permeability and low coercive force. However, permalloy having a high magnetic permeability has a low saturation magnetic flux density of 1.0 T or less, and has a drawback that the overwrite characteristics as a magnetic head cannot be improved. Therefore, in order to increase the saturation magnetic flux density, increasing the Fe content as Fe-Ni based alloy, for example, Ni ₅₆ Fe _44, but the saturation magnetic flux density is improved and 1.6 T, the magnetostriction constant is increased, thereby Noise and signal waveform distortion are likely to occur. On the other hand, as a magnetic pole material having a high saturation magnetic flux density and a small magnetostriction constant, an alloy composition in the vicinity of Co ₇₀ Ni ₂₀ Fe ₁₀ is known. An invention in which such ternary alloy plating is applied to a thin film magnetic head is disclosed in US Pat. No. 4,661,216. However, since these alloy thin films generally have low specific resistance, in the high-frequency range, overcurrent increases, resulting in increased loss, causing heat generation, etc., and greatly reduces magnetic permeability. Is difficult.

[0004] In order to maintain sufficient characteristics even in a high frequency region, a method of increasing the specific resistance of the soft magnetic thin film has been proposed. For example, Hoshino et al. (Summary of the 21st Annual Meeting of the Japan Society of Applied Magnetics (1997), p.312) reported that the saturation magnetic flux density of a plating film containing 3% by weight of P in a Ni-Fe alloy was
1.35T, 80μΩcm specific resistance. However, when the content of P is further increased to further increase the specific resistance, the saturation magnetic flux density is significantly reduced. Hayakawa et al. (J. App
l.Phys. 81 (1997), No.8, p.3747) is Fe-MO (M is Hf, Zr, rare earth element) by a high frequency active sputtering method.
By forming an amorphous film on a cooling plate and heat-treating the film into fine crystals, the coercive force (Hc) is 5 Oe or less, the saturation magnetic flux density is 0.9 T, and the specific resistance is 400 μΩcm or more.
It reports that a soft magnetic film suitable for high frequencies can be obtained. However, such a microcrystalline material becomes extremely brittle due to heat treatment, so when considering application to a magnetic head, it is necessary to process it into a required shape in an as-deposited state, solidify it with an insulating resin, and then perform heat treatment. . However, the heat treatment temperature must be 350 ° C or higher, and the heat-resistant temperature of the insulating resin is about 300 ° C.
It is difficult to apply because it will be much higher than ℃.

[0005] In addition to increasing the specific resistance, laminated films have been studied for high frequency applications. This is because when the film is magnetized in a direction parallel to the plane, a current is induced in the film thickness direction,
Like the laminated iron core of the transformer, the eddy current is suppressed by laminating the films. In this case, the magnetic domain is subdivided by thinning the ferromagnetic material, so that the magnetic permeability in a high frequency range or the coercive force is reduced. In particular, it has been found that a film in which thin layers of Fe and FeN are stacked has high saturation magnetic flux density and excellent high-frequency characteristics, for example, Hoshi et al. (IEEE Trans.
Magn., MAG-26 (1990), p. 2341). However, N in Fe easily diffuses at room temperature or higher, and becomes thermally unstable at a temperature of 200 ° C. or higher.
Such a laminated film has difficulty in heat resistance.

As described above, as a soft magnetic thin film material, a sufficient thin film having a high saturation magnetic flux density, excellent thermal stability, high magnetic permeability in a high frequency range, and low loss can be obtained. Not been.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a soft magnetic thin film having a high saturation magnetic flux density, a high magnetic permeability in a high frequency range, and excellent heat resistance, and a thin film magnetic head using the same. In the offer.

[0008]

SUMMARY OF THE INVENTION A high-frequency magnetic head having a high saturation magnetic flux density, a low loss and a high magnetic permeability in a high-frequency region, is used for writing a high-density magnetic signal to a magnetic medium or for a magnetic head having excellent overwrite properties. A soft magnetic material having excellent characteristics is indispensable. In order to reduce the loss in the high frequency region, it is necessary to minimize the generation of eddy current. For this purpose, it is preferable to increase the electric resistance as much as possible. However, as a method of increasing the electric resistance by using a ferromagnetic thin film material, as described above, if the amount of oxide or P is added and the amount is increased, the saturation magnetic flux is increased. The density is greatly reduced.

In order to obtain a high magnetic permeability or a low coercive force in a high frequency region, it is preferable to make the magnetic domains as small as possible. For this purpose, there is a method using a laminated film. This laminated film has the drawback that a film of a required thickness cannot be obtained in one step, but the addition of other elements can be avoided only to increase the electric resistance to the ferromagnetic material, and the saturation magnetic flux density can be increased. May be higher.

It is known that an iron nitride thin film having a higher saturation magnetic flux density than pure iron can be obtained. However, since this characteristic is lost when the film thickness increases, practically, F
A film in which a plurality of layers of the layer e and the Fe—N alloy are stacked is being studied. It is said that by laminating, a ferromagnetic thin film having high saturation magnetic flux density and excellent characteristics at high frequencies can be obtained. Further, eddy current is suppressed, so that loss can be reduced.

From these viewpoints, Fe, Co and N
Various investigations will be made on a laminated film in which layers of a ferromagnetic metal film composed of at least one of i and layers of a film containing about 10% of nitrogen in these ferromagnetic metals are alternately laminated. did. As a result of forming the laminated film mainly by a sputtering method, a film having a high saturation magnetic flux density, a high magnetic permeability, and a low coercive force could be obtained as it was. However, when processing into a magnetic head, it was necessary to heat it to 320 ° C. to apply the insulating resin, and it was found that the magnetic properties, particularly the magnetic permeability at high frequencies, were greatly reduced by the heating.

Therefore, various investigations were further conducted on the cause of the characteristic deterioration and the countermeasure. In general, when a thin film of a ferromagnetic metal is formed by a sputtering method, the magnetic properties hardly change at a low heating of about 300 ° C., and the magnetic permeability is slightly improved and Hc is reduced. On the other hand, the reason why the magnetic permeability is greatly reduced by heating at such a temperature is that an amorphous or near-fine crystal film is formed as it is, and this may be changed by heating. Estimated. Even when nitrogen diffuses from the nitrogen-containing layer and the laminated structure is dissolved,
Although the magnetic permeability will decrease and the loss will increase at high frequencies, nitrogen diffusion will not occur so quickly with heating at about 300 ° C.

However, it has been considered that in the case of amorphous or fine crystals, a slight decrease in the nitrogen concentration due to diffusion into an adjacent layer further promotes the instability. Therefore, in order to suppress the nitrogen diffusion, the introduction of a layer for suppressing the nitrogen diffusion at the interface between the nitrogen-containing layer and the adjacent layer containing no nitrogen was examined. As a result, it became clear that a layer of an element having a larger standard free energy change in nitride formation than Fe was preferable. That is, Al, Si, Ti, C
By introducing a nitride-forming element such as r, Zr, Nb, Mo, Hf, Ta, W, etc. into the interface between the nitrogen-containing layer and the nitrogen-free layer, the magnetic properties of the laminated film, particularly the magnetic permeability, are reduced. Can be suppressed. This is because these elements have a large affinity for nitrogen, and a stable nitride was formed on the thin layer in contact with the nitrogen-containing layer, and further escape or diffusion of nitrogen was suppressed. Was done. When the heating temperature is higher,
The formation of nitrides of these elements may further progress, and nitrogen in the nitrogen-containing layer may be excessively absorbed. But 400 ° C
In the following heating, nitrides at the interface were hardly observed, but were effective in suppressing the diffusion of nitrogen, and were able to suppress the deterioration of the magnetic properties due to the heat treatment.

Further, the nitride formed at the interface between the nitrogen-containing layer and the nitride-forming element layer is an insulator having an extremely high electric resistance value, whereby conduction between the two layers is inhibited and eddy current is suppressed. Is done. This was also considered to be effective in improving magnetic permeability and reducing loss in a high frequency range.

Based on these findings, the present invention was completed by further elucidating the limits of each composition and the constitution thereof. The gist of the present invention is as follows. (1) Soft magnetism in which ferromagnetic thin layers composed of at least one of Fe, Co, and Ni and ferromagnetic thin layers composed of an alloy containing N in at least one of Fe, Co, and Ni are alternately laminated. A thin film comprising Al, Si, Ti, C
A soft magnetic laminated film comprising r, Zr, Nb, Mo, Hf, Ta, W, or a nitride of any of these elements as a nonmagnetic layer. (2) A thin-film magnetic head characterized in that the soft magnetic laminated film of (1) is used for a write pole portion or an element shield portion.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown schematically in FIG. 1, a soft magnetic film of the present invention comprises a first ferromagnetic layer 2 comprising at least one of Fe, Co and Ni, And N
i, the second ferromagnetic layers 3 containing N in addition to one or more of the layers i are alternately stacked, and Al, Si, Ti, Cr, Zr, Nb, Mo, H
This is a laminated film in which a nitrogen diffusion preventing layer 1 made of f, Ta, W, or a nitride of these elements is present.

The thickness of each of the first ferromagnetic layer and the second ferromagnetic layer is preferably in the range of 5 to 20 nm. This is because the saturation magnetic flux density decreases when the thickness is 5 nm or less. On the other hand, when the thickness exceeds 20 nm, characteristics in a high frequency range such as a decrease in magnetic permeability and an increase in coercive force deteriorate.

The thickness of the diffusion preventing layer 1 between the first ferromagnetic layer 2 and the second ferromagnetic layer 3 is desirably 1 to 3 nm. The diffusion prevention layer prevents the nitrogen in the second ferromagnetic layer from diffusing into the first ferromagnetic layer when heated, thereby preventing the effect of nitrogen from being reduced or eliminated. 1nm thick
If it is less than 3, the effect of suppressing the diffusion of nitrogen from the second ferromagnetic layer is insufficient, and if it exceeds 3 nm, the magnetic flux density as a laminated film becomes insufficient, so it is better to be 1 to 3 nm. .

As described above, the soft ferromagnetic film is formed by repeating the stacking of the first ferromagnetic layer 2, the diffusion preventing layer 1, the second ferromagnetic layer 3 containing nitrogen, and the diffusion preventing layer 1. I do. The number of repetitions of this lamination is desirably at least 5 or more in order to obtain the desired magnetic properties, and the thickness of the laminated film can be applied to those having a thickness of about 300 to 5000 nm.

The composition of the first ferromagnetic layer is made of at least one of Fe, Co and Ni. By using these elements, a high saturation magnetic flux density and a high magnetic permeability can be obtained. Each of these elements may be used alone, or two or more alloys may be used. It is more preferable to use a composition generally used as a high-permeability ferromagnetic alloy. For example, in the case of a Co-Fe alloy, if Fe is in the range of 10 to 15 atomic%, the magnetic properties will be more excellent.
If the alloy is a Fe-Ni-Co alloy, the Fe content is 10 to
It is preferable in terms of characteristics that the alloy composition is 15 atomic%, Ni is 10 to 20 atomic%, and the balance is Co.

The composition of the second ferromagnetic layer is as follows. Nitrogen is added to at least one of Fe, Co and Ni.
% By weight. Nitrogen is included because a high saturation magnetic flux density can be obtained by stacking with a layer containing no nitrogen, and a decrease in magnetic permeability in a high frequency range can be suppressed. In this case, if the nitrogen content is less than 2% by weight, these effects cannot be obtained, and even if the nitrogen content is 15% by weight or more, the effect is saturated. The composition of the first ferromagnetic material and the composition of the second ferromagnetic material excluding nitrogen may be the same or different. However, it is preferred that these two ferromagnetic layers have the same composition if possible.

The laminated film is preferably formed by a sputtering method. In the case of a ferromagnetic layer, an element or alloy material having such a ferromagnetic composition is targeted. The nitrogen-containing ferromagnetic layer is formed by sputtering in a nitrogen atmosphere using the alloy material having the ferromagnetic composition as a target.
The amount of nitrogen in the film is controlled by changing the nitrogen concentration in the atmosphere in which the sputtering is performed.

Between the first and second ferromagnetic layers, Al, Si, Ti, Cr, Zr, Nb, Mo,
A nitrogen diffusion preventing layer made of Hf, Ta, W, or a nitride of these elements is present. This layer may be formed by a sputtering method similarly to the two ferromagnetic layers. This layer may be one of the above elements, an alloy of two or more of the above elements, a metal, a nitride, or a mixture of a metal and a nitride. In the case of metal, a nitride film is formed on the contact surface with the ferromagnetic layer containing nitrogen to prevent further diffusion of nitrogen. If nitride is used, nitrogen absorption from the ferromagnetic layer containing nitrogen can be suppressed. When forming a metal film, the atmosphere of the sputtering may be an inert gas such as argon or vacuum, and when forming a nitride, the atmosphere may contain nitrogen.

When the soft magnetic laminated film obtained as described above is applied to a magnetic head, it is necessary to form the magnetic pole by a process such as milling after forming the film on a substrate, or to use a photolithographic technique to form the magnetic pole. What is necessary is just to form a film in the shape which does.

[0025]

EXAMPLE A high-frequency magnetron sputtering apparatus was used as a film forming apparatus, and a soft magnetic laminated film was formed on a 2-inch square glass substrate. The ultimate vacuum before film formation is 10 ⁻⁵ Torr or less, the gas pressure during sputtering is 5 × 10 ⁻³ Torr, and the sputtering power is 1 kW. The target for forming the ferromagnetic layer is Fe, Co ₃₀ Fe ₇₀ , or Co ₉₀ Fe ₁₀
And the atmosphere was argon. Nitrogen-containing ferromagnetic layer, the same target, nitrogen partial pressure in the atmosphere 8vol%
I made it. This allowed the layer to contain about 10% by weight of nitrogen. Further, as a nitrogen diffusion preventing layer, A
1, Si, Ti, Cr, Zr, Nb, Mo, Hf, T
In the same manner, a and W were formed in an argon atmosphere by sputtering. The combination of the ferromagnetic layer / nitrogen diffusion preventing layer / nitrogen-containing ferromagnetic layer / nitrogen diffusion preventing layer was repeated 20 times in the example of the present invention to form a laminated film. Also, F
As a comparative example, a single film in which a fine precipitate of ZrN was dispersed in e and a laminated film without a nitrogen diffusion preventing layer were prepared.

The obtained laminated film is further subjected to 50
Heat treatment was performed in a vacuum at 320 ° C. for 3 hours by applying an Oersted magnetic field, and the magnetic properties before and after the heat treatment were investigated. The magnetic properties were measured by measuring the saturation magnetic flux density with a vibrating magnetometer (VSM) and measuring the Hc with a parallel line permeability meter.
And the magnetic permeability in the high frequency range (500 MHz) was measured. Table 1 shows the configuration of the soft magnetic layered film and the measurement results of the magnetic properties before and after the heat treatment. Although the magnetic permeability is greatly reduced by the heat treatment at 320 ° C., the results of Test Nos. 2 to 17 of the present invention example having a nitrogen diffusion preventing layer are compared with the results of Test No. 1 having no nitrogen diffusion preventing layer. The degree of the decrease is much smaller, and the obtained characteristic values indicate that the film is a soft magnetic film having excellent high frequency characteristics.

[0027]

[Table 1]

[0028]

The soft magnetic thin film of the present invention has a high saturation magnetic flux density, has a high magnetic permeability in a high frequency range, and has excellent heat resistance. A thin-film magnetic head using this as a write magnetic pole or a shield has excellent performance without deteriorating the magnetic properties of the magnetic film due to heating in the process of manufacturing the magnetic head.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a part of the structure of a soft magnetic laminate according to the present invention for describing the soft magnetic laminate.

[Explanation of symbols]

1 nitrogen diffusion preventing layer, 2 first ferromagnetic layer, 3
Second ferromagnetic layer

Claims (2)

[Claims] A soft magnetic layer comprising a ferromagnetic layer composed of at least one of Fe, Co, and Ni and a ferromagnetic layer composed of an alloy containing N in at least one of Fe, Co, and Ni. Al, Si, Ti, C between these two ferromagnetic layers
A soft magnetic laminated film characterized in that at least one selected from the group consisting of r, Zr, Nb, Mo, Hf, Ta, W, and nitrides of these elements is present as a nonmagnetic layer. 2. A thin-film magnetic head, wherein the soft magnetic laminated film according to claim 1 is used for a write pole portion or an element shield portion.