JPH07169620A - Magnetic thin film and magnetic head using the same - Google Patents

Abstract

PURPOSE:To raise the corrosion resistance while securing desired magnetic property by putting the change of saturation magnetic flux density and the coercive force at the time of adding first additive element to a magnetic film and the change of saturation magnetic flux density and the coercive force at the time of adding only the second additive element in such relation as to compensate each other. CONSTITUTION:In a magnetic film, which contains Fe as a main ingredient, Ta in the range from 5atom% to 20atom%, and C in the range from 1atom% to 20atom%, it contains first and second additive elements, and the change of the saturation magnetic flux density and the coercive force at the time of having added only the first additive element to it and the change of the saturation magnetic flux density and the coercive force at the time of having added only the second additive element to it are in the relation of compensating each other. And, the first additive element is at least one kind among Cr, Al, Nb, Mo, and Ru, and the quantity of addition is in the range from 0.5atom% to 8 atom %, and also the second additive element is N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic thin film and a magnetic head using the magnetic thin film.

[0002]

2. Description of the Related Art With the progress of the advanced information society in recent years, there is an increasing need for a compact and high-density storage device. Under such circumstances, research on high-density recording and downsizing of magnetic recording devices has been rapidly advanced.

In order to realize high-density recording in a magnetic recording apparatus, a magnetic recording medium having a high coercive force and a high-performance magnetic head capable of recording information on this medium are required in order to make recorded fine magnetic domains stably exist. . In order to sufficiently magnetize a high coercive force magnetic recording medium to record a signal (information), a magnetic head material capable of generating a strong magnetic field corresponding thereto, that is, a magnetic head material having a high saturation magnetic flux density is required. .

Fe-C and Fe-N materials have been proposed to date as materials having such a high saturation magnetic flux density. However, these materials
Since magnetic properties (especially coercive force and saturation magnetic flux density) are easily changed by reacting with oxygen and water in the atmosphere to form hydroxides and oxides, magnetic heads made of these materials should be used during use. Performance may be reduced.

Therefore, it has been proposed to add an element for improving the corrosion resistance to Fe—C type or Fe—N type materials in order to suppress the fluctuation of the magnetic characteristics. The soft magnetic alloy film disclosed in Kaihei 3-20444 can be mentioned. The composition formula of this soft magnetic alloy film is Fe _x M _z C _w (M = Ti, Zr, H
(one or more of f, Nb, Ta, Mo and W)
The average grain size is basically 0.008.
It is composed of crystal grains of μm or less, and a part thereof contains a crystal phase of a carbide of the element M.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the soft magnetic alloy film disclosed in Japanese Patent No. 444, it may be difficult to achieve both the magnetic characteristics optimized by addition of elements and compositional adjustment and the concentration of additional elements required for improving corrosion resistance. There is. That is, when the corrosion resistance is secured, the magnetic characteristics (particularly the saturation magnetic flux density and the coercive force) are lowered, and conversely, when the magnetic characteristics are secured, the corrosion resistance is lowered. If the magnetic characteristics deteriorate, an error or noise may occur when information is recorded by a magnetic head using the magnetic characteristics.

Therefore, the object of the present invention is to improve the corrosion resistance while maintaining the magnetic characteristics of Fe-Ta.
It is to provide a -C type magnetic thin film.

Another object of the present invention is to provide a magnetic head having higher reliability than ever before.

[0009]

[Means for Solving the Problems]

(1) The first magnetic thin film of the present invention is a magnetic thin film containing Fe as a main component, Ta in the range of 5 atom% to 20 atom%, and C in the range of 1 atom% to 20 atom%, Changes in saturation magnetic flux density and coercive force that occur when only the first additive element is added to the magnetic thin film, including the first and second additive elements, and only the second additive element is added to the magnetic property. It is characterized in that the saturation magnetic flux density and the change in coercive force that occur when added to the thin film have a relationship of compensating each other.

The first additive element is Cr, Al, N.
at least one selected from the group consisting of b, Mo and Ru, the addition amount of which is in the range of 0.5 atom% to 8 atom%, and the second additive element is N. preferable.

Among these additive elements, the effect is particularly great when two elements Cr and Ru are used as the first additive element and N is used as the second additive element.

Further, in the magnetic thin film of the present invention, it is preferable that the saturation magnetic flux density is equal to the saturation magnetic flux density when the first and second additive elements are not added. In this case, the saturation magnetic flux density is preferably 1.5 Tesla or more. Since this value is the same as the saturation magnetic flux density when the first and second additive elements are not included, the corrosion resistance is maintained while maintaining the same magnetic characteristics as when the first and second additive elements are not added. Can be improved.

(2) The first magnetic thin film of the present invention is F
In a magnetic thin film containing e as a main component, Ta in the range of 5 atom% to 20 atom% and C in the range of 1 atom% to 20 atom%, the first and second additive elements are included, Changes in saturation magnetic flux density and coercive force generated when only the first additive element is added to the magnetic thin film, and saturation magnetic flux density and coercive force generated when only the second additive element is added to the magnetic thin film. Of the first additive element is Cr, A
at least one selected from the group consisting of 1, Nb, Mo and Ru, the addition amount of which is in the range of 0.5 atom% to 8 atom%, and the second additive element is N Furthermore, the structure of the magnetic thin film has an average grain size of 1
It is characterized in that it contains crystal grains of 0 nm or less.

The crystal grains are mainly αFe crystals, but also include TaC crystals. The reason why the average particle diameter is 10 nm or less is that good magnetic characteristics can be obtained in this range.

The crystal grains can be easily deposited, for example, by performing heat treatment after film formation.
Other methods may be used as long as the same effect can be obtained. The crystal grains are deposited in consideration of the fact that glass bonding is performed when assembling a magnetic head using the magnetic thin film.

In the second magnetic thin film, N as the second additive element is usually distributed almost uniformly as an interstitial solid solution or nitride throughout the thin film, or segregated at the grain boundaries of the crystal. To do. This N suppresses the growth of the crystal grains.

The nitride is a nitride of the first additive element, for example, AlN, Cr ₂ N, TaN, Ta ₂ N,
MoN ₂ , NbN, Fe ₂ N, Fe ₄ N, Mo ₂ N, Nb ₂
N.

Further, it is preferable that there is a concentration gradient of N in the film thickness direction. In this case, there is an effect that oxygen can be further suppressed from diffusing in the thin film.

The concentration gradient of N in the film thickness direction is preferably such that the concentration increases from the inside of the thin film toward the surface. This is because the effect of suppressing corrosion is greatest.

Plural kinds of nitrides may exist inside the thin film. These nitrides usually have a concentration gradient because they have different diffusivities at the time of crystal grain precipitation. Since the concentration gradient has an action of suppressing diffusion of oxygen in the film, there is an advantage that the progress of the corrosion reaction is further suppressed. Examples of this nitride include TaN, N-Ta-C, (TaN
b) N, NbN, etc.

Preferably, Fe, Ta and part of the first additional element are segregated as carbides at the grain boundaries of the crystal. In other words, all C constitutes carbide and is not bonded to Fe. This is because good magnetic characteristics can be obtained.

The above-mentioned carbide is, for example, TaC, Fe ₃ C,
Cr ₃ C ₂ , Mo ₂ C, MoC, Cr ₇ C ₃ , Cr ₄ C, Nb
C, Nb ₂ C and AlC.

The metal element such as Fe, Ta, Cr, Al, Nb, Mo and Ru may or may not have a chemical bond with N or C.

N as the second additive element can be easily added by forming a film by sputtering in an atmosphere containing N. Also, during film formation, N
By changing the gas concentration of, it is possible to easily form a concentration gradient of N in the thin film.

(3) The magnetic head of the present invention is characterized by including the magnetic thin film described in (1) or (2) above. This magnetic thin film is used for all or part of the core of the magnetic head.

[0026]

In general, when an element is added to the magnetic thin film, the magnetic characteristics, particularly the saturation magnetic flux density and coercive force, which are important as the characteristics of the magnetic head, deteriorate.

In the magnetic thin film of the present invention, changes in the saturation magnetic flux density and the coercive force that occur when only the first additive element is added to the magnetic thin film, and when only the second additive element is added to the magnetic thin film. Since the changes in the saturation magnetic flux density and the coercive force that occur in 1) have a relationship of compensating for each other, adjusting the addition amounts of the first and second additive elements improves the corrosion resistance while maintaining the desired magnetic characteristics. be able to.

In the magnetic head of the present invention, since the magnetic thin film having improved corrosion resistance while ensuring desired magnetic characteristics is used, higher reliability than before can be obtained.

[0029]

EXAMPLES The present invention will be described in more detail below with reference to examples.

[Example 1] The magnetic thin film of this example uses two elements, Cr and Ru, as the first additive element and N as the second additive element, and is manufactured as follows. .

First, Cr is deposited on the FeTaC alloy target.
Using a composite target in which targets of Ru and Ru are uniformly arranged, Ar gas containing 0.5% of N ₂ gas is used as discharge gas, discharge gas pressure: 6 mTorr, input RF power: 4
Sputtering was performed at 00 W to obtain an alloy thin film.

Next, this alloy thin film was heat-treated at 590 ° C. for 1 hour and annealed. This is because the glass bonding process is included in the process of manufacturing the magnetic head.

The composition of the magnetic thin film obtained by annealing was Fe ₇₃ Ta ₇ C ₁₀ Cr ₇ Ru ₃ N _x . Since it was difficult to quantify N, its content is unknown, but it is estimated that x ≦ 0.1 atomic% in view of the fact that quantification is impossible.

When the ESCA spectrum of the element contained in this magnetic thin film was measured, there were three kinds of peaks in the spectrum. These peaks are respectively those in which N is present in atomic form, and the first additive elements Cr and Ru.
It is presumed that it is based on those existing as a nitride of and a combination of N and C and a metal element (Fe, Ta, Cr or Ru).

When the magnetic characteristics of this magnetic thin film were measured, the saturation magnetic flux density was 1.71 T and the coercive force was 0.30.
Oe, relative permeability is 4200 (1 MHz), magnetostriction constant is 5
It was × 10 ^-7 .

The corrosion resistance of this magnetic thin film was investigated as follows. The magnetic thin film was immersed in city water (tap water) aerated with 60 ° C. air and tap water of 0.1 N, and the change with time in magnetic characteristics was measured. Here, the magnetic characteristics were evaluated by the saturation magnetic flux density, which is an important parameter as a head material.

In addition, the temporal change of the corroded area (discolored area) on the surface of the magnetic thin film was directly measured. The results are shown in FIGS. 1 and 2, respectively.

From FIGS. 1 and 2, the magnetic thin film of this example showed no change in both the magnetic properties and the corroded area regardless of which water was used. Therefore, it can be seen that it has excellent corrosion resistance.

Next, the magnetic thin film having the above structure was formed on a ferrite substrate and assembled as a MIG (Metal In Gap) type magnetic head shown in FIG.

In FIG. 5, the magnetic thin film 1 obtained as described above is formed on the surface of the ferrite substrate 2.
Two ferrite substrates 2 with the same structure are lead glass 4
It is joined and integrated via. The two magnetic thin films 1 are arranged to face each other, and a gap 3 is formed between the magnetic thin films 1 on the sliding surface of the magnetic head. A coil (not shown) is wound around the magnetic head through the through hole 5 in the central portion.

The magnetic head having the structure shown in FIG.
The sample was left to stand in an environment of reciprocating between 30 ° C. and the change with time of the reproduced signal was examined. In this environment, dew condensation was observed on the magnetic head because the humidity was not controlled. At that time, recording / reproduction was performed as a high-definition digital VTR and the change in signal output was examined.

As a result, even when the heat cycle was repeated 100 times or more, the reproduced signal output was constant at 40 dB and no change was observed. Therefore, it was found that this magnetic head has excellent corrosion resistance and maintains good magnetic characteristics even under the above-mentioned environment.

Since this magnetic head has a high saturation magnetic flux density, it is suitable for high density magnetic recording, and particularly suitable for a high definition digital VTR magnetic head.

[Comparative Example 1] When manufactured under the same conditions as in Example 1 except that a pure Ar atmosphere containing no N was used,
The magnetic characteristic of the magnetic thin film is that the saturation magnetic flux density is 1.38.
T, coercive force 0.78 Oe, relative permeability 2900 (1M
Hz), magnetostriction constant was 1 × 10- ^6. This is not sufficient for a magnetic head. Therefore, in order to improve the magnetic characteristics (especially the saturation magnetic flux density) and make it equal to that of the first embodiment, the concentrations of Cr and Ru may be reduced. Therefore, by adjusting the composition, the composition is changed to Fe ₇₅ Ta ₈ C ₁₁
A magnetic thin film of Cr ₄ Ru ₂ was manufactured as Comparative Example 1. When the magnetic characteristics of this thin film were measured, the saturation magnetic flux density was 1.
51T, coercive force 0.51 Oe, relative permeability 3500
(1 MHz), the magnetostriction constant was 8 × 10 ⁻⁷ .

Using the magnetic thin film of Comparative Example 1, a magnetic head having the structure shown in FIG. 5 was manufactured, and the magnetic head was used to examine the corrosion resistance of the magnetic thin film in the same manner as in Example 1. The results are shown in FIGS. 1 and 2, respectively.

As can be seen from FIGS. 1 and 2, in the magnetic thin film of Comparative Example 1, the saturation magnetic flux density decreases and the coercive force increases with the passage of time. Also, it can be seen that the corroded area increases with the passage of time, and the corrosion progresses. Therefore, it is clear that Comparative Example 1 is inferior to Example 1 in corrosion resistance.

Example 2 The magnetic thin film of this example uses two elements, Cr and Nb, as the first additive element and N as the second additive element, and is manufactured as follows. .

First, a FeTaC alloy was used for a composite target in which Cr and Nb were uniformly arranged, and N ₂ gas was adjusted to 0.
Discharge gas pressure: 6 with Ar gas containing 5% as discharge gas
Sputtering was performed at mTorr and applied RF power of 400 W to obtain an alloy thin film. Next, this alloy thin film was heat-treated at 590 ° C. for 1 hour and annealed.
The composition of the obtained magnetic thin film was Fe ₇₃ Ta ₇ C ₁₀ Cr ₇ N
It was b ₄ N _x. In this case as well, it was difficult to quantify N, so the content thereof is unknown, but it is estimated that x ≦ 0.1 atom% from the viewpoint that quantification is impossible.

When the ESCA spectrum of the element contained in this magnetic thin film was measured, there were three types of peaks in the spectrum. These peaks are respectively those in which N is present in atomic form, those present as nitrides of additional elements, that is, Cr and Nb, and N and C are bonded to metallic elements (Fe, Ta, Cr or Nb). It was presumed to be based on things.

When the magnetic characteristics of this magnetic thin film were measured, the saturation magnetic flux density was 1.65 T and the coercive force was 0.40.
Oe, relative permeability is 3900 (1 MHz), magnetostriction constant is 6
It was × 10 ^-7 .

The corrosion resistance of this magnetic thin film was examined in the same manner as in Example 1. The results regarding the saturation magnetic flux density are shown in FIG. 3, and the results regarding the change over time of the corroded area (discolored area) of the film surface are shown in FIG.

As shown in FIGS. 3 and 4, the magnetic thin film of Example 2 showed no change in both the magnetic properties and the corroded area regardless of which water was used. Therefore, it can be seen that it has excellent corrosion resistance.

Next, using this magnetic thin film, M shown in FIG.
The IG type magnetic head was assembled, and the change with time of the signal output was obtained under the same conditions as in Example 1. As a result, even when this heat cycle was repeated 100 times or more, the reproduced signal output was constant at 39 dB, and no change was observed. Therefore, it was found that this magnetic head also has excellent corrosion resistance and maintains good magnetic characteristics even under the above environment.

[Comparative Example 2] When manufactured under the same conditions as in Example 2 except that a pure Ar atmosphere containing no N was used,
The magnetic characteristics of the obtained magnetic thin film have a saturation magnetic flux density of 1.2.
9T, coercive force 0.68 Oe, relative permeability 2500 (1
MHz) and the magnetostriction constant was 1.5 × 10 ⁻⁶ . This is not sufficient for a magnetic head. Therefore, in order to improve the magnetic characteristics (especially the saturation magnetic flux density) and make it equal to that of the first embodiment, the concentrations of Cr and Nb may be reduced. Therefore, by adjusting the composition, the composition is changed to Fe ₇₅ Ta ₈ C.
A magnetic thin film of ₁₁ Cr ₄ Nb ₂ was manufactured as Comparative Example 2. When the magnetic characteristics of this thin film were measured, the saturation magnetic flux density was 1.51 T, the coercive force was 0.51 Oe, and the relative permeability was 350.
The magnetostriction constant was 0 (1 MHz) and 8 × 10 ⁻⁷ .

A magnetic head having the structure shown in FIG. 5 was manufactured using the magnetic thin film of Comparative Example 2, and the corrosion resistance of the magnetic thin film was examined by using the magnetic head in the same manner as in Example 2. The results are shown in FIGS. 3 and 4, respectively.

As can be seen from FIGS. 3 and 4, in the magnetic thin film of Comparative Example 2, the saturation magnetic flux density decreased with the passage of time. (Although not shown, the coercive force increased as in Comparative Example 1.) Further, it can be seen that the corroded area increased with the passage of time, and the corrosion proceeded. Therefore, it is clear that Comparative Example 2 is inferior to Example 2 in corrosion resistance.

[0057]

According to the present invention, it is possible to obtain a Fe-Ta-C magnetic thin film having improved corrosion resistance while maintaining magnetic characteristics. ◆ Also, a magnetic head having higher reliability than before can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing changes with time in magnetic characteristics when the magnetic thin films of Example 1 and Comparative Example 1 of the present invention were immersed in water.

FIG. 2 is a graph showing changes with time in the corroded area when the magnetic thin films of Example 1 and Comparative Example 1 of the present invention were immersed in water.

FIG. 3 is a graph showing changes over time in magnetic characteristics when the magnetic thin films of Example 2 and Comparative Example 2 of the present invention were immersed in water.

FIG. 4 is a graph showing changes over time in the corroded area when the magnetic thin films of Example 2 and Comparative Example 2 of the present invention were immersed in water.

FIG. 5 is a diagram showing a magnetic head using the magnetic thin film of Example 1 of the invention.

[Explanation of symbols]

 1 Magnetic thin film 2 Ferrite substrate 3 Gap 4 Lead glass 5 Through hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidetoshi Moriwaki 1-280, Higashi Koikekubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (15)

[Claims] 1. A magnetic thin film containing Fe as a main component and Ta in the range of 5 atom% to 20 atom% and C in the range of 1 atom% to 20 atom%. And changes in saturation magnetic flux density and coercive force that occur when only the first additional element is added to the magnetic thin film, and saturation that occurs when only the second additional element is added to the magnetic thin film. A magnetic thin film characterized in that a change in magnetic flux density and a change in coercive force have a relationship of compensating each other. 2. The first additive element is Cr, Al, N
at least one selected from the group consisting of b, Mo and Ru, the addition amount of which is in the range of 0.5 atom% to 8 atom%, and the second additive element is N. 1. The magnetic thin film described in 1. 3. The magnetic thin film according to claim 2, wherein the first additional element is two elements of Cr and Ru. 4. The magnetic thin film according to claim 1, wherein the saturation magnetic flux density is equal to the saturation magnetic flux density when neither the first additive element nor the second additive element is added. 5. The magnetic thin film according to claim 4, wherein the saturation magnetic flux density is 1.5 tesla or more. 6. A magnetic thin film containing Fe as a main component and Ta in the range of 5 atom% to 20 atom% and C in the range of 1 atom% to 20 atom%, wherein the first and second additive elements are included. And changes in saturation magnetic flux density and coercive force that occur when only the first additional element is added to the magnetic thin film, and saturation that occurs when only the second additional element is added to the magnetic thin film. The magnetic flux density and the change in coercive force have a relationship of compensating each other, and the first additive element is Cr, Al, Nb, Mo or R.
at least one selected from the group consisting of u, the addition amount thereof is in the range of 0.5 atom% to 8 atom%, and the second additive element is N, and A magnetic thin film, wherein the structure of the magnetic thin film includes crystal grains having an average grain size of 10 nm or less. 7. The magnetic thin film according to claim 6, wherein N as the second additional element is present substantially uniformly throughout the magnetic thin film as either an interstitial solid solution or a nitride. 8. The magnetic thin film according to claim 6, wherein N as the second additional element is segregated at a grain boundary of the crystal as either an interstitial solid solution or a nitride. 9. The magnetic thin film according to claim 6, wherein Fe, Ta, and part of the first additional element are segregated as carbides in the grain boundaries of the crystal. 10. The magnetic thin film according to claim 6, wherein there is a concentration gradient of N as the second additive element in the film thickness direction. 11. The magnetic thin film according to claim 10, wherein the concentration of N as the second additive element in the film thickness direction increases from the inside of the magnetic thin film toward the surface thereof. 12. The first additive element is Cr and Ru.
The magnetic thin film according to claim 6, wherein the magnetic thin film is 2 elements. 13. The saturation magnetic flux density is the same as the first and second magnetic flux density.
13. The magnetic thin film according to any one of claims 6 to 12, which has a saturation magnetic flux density equal to that in the case where neither of the additive elements of <1> is added. 14. The magnetic thin film according to claim 13, wherein the saturation magnetic flux density is 1.5 tesla or more. 15. A magnetic head comprising the magnetic thin film according to claim 1. Description: