JPH07235007A - Soft magnetic thin film, magnetic head and magnetic recording apparatus using the same - Google Patents

Abstract

PURPOSE:To improve the corrosion and wear resistances of a soft magnetic thin film while maintaining its magnetic characteristics. CONSTITUTION:The soft magnetic thin film 10 is composed of a nonmagnetic 1st layer 12 disposed on the surface side and a soft magnetic 2nd layer 13 disposed adjacent to the 1st layer 12 at the inside of the layer 12. The hardness of the 1st layer 12 is higher than that of the 2nd layer 13. The objective soft magnetic thin film having improved corrosion and wear resistances while maintaining its magnetic characteristics is obtd. When this soft magnetic thin film is used, the durability and reliability of a magnetic head and a magnetic recorder are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic thin film, a magnetic head and a magnetic recording device, more specifically,
The present invention relates to a soft magnetic thin film having excellent wear resistance and corrosion resistance, and a magnetic head and a magnetic recording device using the soft magnetic thin film.

[0002]

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

To realize high density recording, a magnetic recording medium having a high coercive force and a magnetic head having a high saturation magnetic flux density are required. Fe-C type, Fe-N type, and the like are currently known as this kind of magnetic head material. These materials have a problem that during use, they react with oxygen and water in the atmosphere to form hydroxides and oxides, and magnetic characteristics (especially coercive force and saturation magnetic flux density) fluctuate. .

Therefore, in order to put a magnetic head using these materials into practical use, it is necessary to suppress fluctuations in magnetic characteristics. Therefore, conventionally, elements other than magnetic elements have been added to improve corrosion resistance. Magnetic head materials have been proposed (see, for example, Japanese Patent Laid-Open No. 3-20444).

[0005]

In the above-mentioned known magnetic head materials, it is difficult to achieve a balance between the magnetic characteristics optimized by the addition of elements and the compositional adjustment and the concentration of the additional element necessary for improving the corrosion resistance. There is a problem that sometimes. That is, if the corrosion resistance is secured, the magnetic characteristics (particularly the saturation magnetic flux density and the coercive force) may be deteriorated, which may cause an error or noise when recording. On the contrary, if the magnetic properties are secured, sufficient corrosion resistance cannot be obtained.

Further, when it is applied to a magnetic recording medium such as a VTR device that comes into contact with a moving magnetic recording medium, there is a problem that the sliding surface may be worn due to long-term use.

Therefore, an object of the present invention is to provide a soft magnetic thin film capable of improving corrosion resistance and abrasion resistance while maintaining optimized magnetic characteristics.

Another object of the present invention is to provide a magnetic head and a magnetic recording device having excellent durability and high reliability.

[0009]

[Means for Solving the Problems]

(1) The soft magnetic thin film of the present invention comprises a non-magnetic first layer disposed on the front surface side and a soft magnetic second layer disposed inside and adjacent to the first layer, The hardness of the first layer is higher than the hardness of the second layer.

Preferably, the first layer is made of Ti, Ta,
It is formed of a compound of at least one element selected from the group consisting of Cr, Mo, W, Zr, Hf and V or a mixture thereof, and the compound is a nitride of the element,
At least one of carbide and oxide is used.

For example, for nitride, TiN, TaN, C
For rN, MoN, WN, ZrN, HfN, VN, and carbides, FeC, Fe ₃ C, TiC, TaC, CrC, Mo.
C, WC, ZrC, HfC, VC, TiO for oxides
₂ , Ta ₂ O ₃ , Cr ₂ O ₃ , MoO ₃ , WO ₃ , ZrO ₂ , H
Examples thereof include fO ₂ and VO ₃ . But other compounds,
For example, FeN, Fe ₂ O ₃ and FeO can be used. The names listed here are examples, and the composition ratio of each element may deviate from the composition ratio represented by these chemical formulas.

The soft magnetism used as the second layer is not particularly limited. Fe-C system, Fe-Ta system, Fe-N
Any type such as a Co type and a Co type can be used. For example, the following may be mentioned. (⇒ please add) Fe-C system, FeTaC, FeNbC, FeTaC
Cr, FeTaCCrNb, FeTaCCrRu, Fe
FeTaN and FeTaCrN are used in the -N system, and CoTaZr and CoNbZr are used in the Co system.

Preferably, the second layer is made of a soft magnetic material containing Fe as a main component and Ta and C. In this case, the first layer is preferably formed of TiN.

The second layer may also be formed of a soft magnetic material containing Co as a main component and further containing Nb and Zr.
In this case, the first layer is preferably made of CrN.

The thickness of the first layer is 1 nm or more and 10 n.
It is preferably m or less. If it is less than 1 nm, the effect of improving the corrosion resistance and abrasion resistance cannot be obtained, and if it is more than 10 nm, the spacing between the magnetic recording medium and the soft magnetic second layer becomes wide, and the writing characteristics to the magnetic recording medium are improved. Because it deteriorates. Within this range, more than 5 nm and 10 nm or less is more preferable, and 1 nm or more and 5 nm or less is most preferable.

At the interface between the first layer and the second layer, it is not necessary for the two layers to be clearly separated. At the interface, a layer of a mixture of the constituent elements of the first layer and the constituent elements of the second layer is usually formed. In this case, the thickness of the first layer is considered including the mixed layer.

The first layer is preferably formed on the second layer by any one of a sputtering method, an ion plating method and an ion mixing method. This is because any of these methods can easily form a layer and is suitable for mass production.

Of the above methods, the sputtering method is more preferable. This includes not only ordinary sputtering methods but also reactive sputtering methods. This is because there is an advantage that the possibility of damage in the step of forming the second layer and damage during use can be significantly reduced. Also, the adhesive force between the first layer and the second layer is sufficient.

The first layer may be formed entirely on one side of the second layer or may be partially formed. For example, when the soft magnetic thin film is applied to a magnetic head, the first layer may be formed only in a portion that slides on the magnetic head.

When the first layer is partially formed on one side of the second layer, it is preferable that the second layer is formed by an ion mixing method. This is because the adhesive force between the first layer and the second layer is further increased and damage to the second layer can be suppressed.

(2) The magnetic head of the present invention is characterized by including the soft magnetic thin film of (1) above. The structure and material of the magnetic head other than the soft magnetic thin film are not particularly limited.

The soft magnetic thin film is preferably arranged in a gap formed in the core of the magnetic head. That is, a so-called MIG (Metal In Gap) type magnetic head is preferable.

Preferably, the first layer of the soft magnetic thin film is
It is arranged so as to contact a moving magnetic recording medium. This is because the effects of this invention are effectively exhibited.

(3) The magnetic recording apparatus of the present invention is characterized by including the magnetic head of the above (2).

(4) The type and structure of the magnetic recording medium used in the magnetic recording apparatus of the present invention is not particularly limited. For example, it may be a magnetic tape or a magnetic disk. Further, the magnetic head may be in contact with or separated from the magnetic recording medium.

[0026]

In the soft magnetic thin film of the present invention, since the first layer is arranged on the surface side of the second layer, the second layer becomes inactive against corrosive components such as oxygen and water in the atmosphere. Therefore,
Fluctuations in the magnetic properties of the second layer due to these corrosive components can be suppressed, and the corrosion resistance of the second layer also improves.

Further, since the first layer having a hardness higher than that of the second layer is arranged on one side of the second layer, the friction coefficient on the surface of the soft magnetic thin film is reduced as compared with the case where the first layer is not provided. As a result, wear of the soft magnetic thin film due to contact with the magnetic recording medium can be suppressed in combination with the high hardness of the first layer.

Therefore, it is possible to improve the corrosion resistance and the wear resistance while maintaining the optimized magnetic characteristics.

Since the magnetic head and the magnetic recording apparatus of the present invention have the above-mentioned soft magnetic thin film, high corrosion resistance and wear resistance can be obtained while maintaining optimized magnetic characteristics. As a result, durability and reliability are improved.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Example 1 In this example, Fe was used as the soft magnetic second layer.
Using a TaCRuCr alloy film, T as the first layer of high hardness
It uses an iN film.

FIG. 1 shows the cross-sectional structure of the soft magnetic thin film 10 of this embodiment. The soft magnetic thin film 10 is a soft magnetic layer 12 made of a FeTaCRuCr alloy film formed on a substrate 11.
And a high hardness layer 13 made of a TiN film formed on the soft magnetic layer 12. The thickness of the soft magnetic layer 12 is 5 μm, and the thickness of the high hardness layer 13 is 5 nm.

The soft magnetic thin film 10 having the above structure was formed by the usual (non-reactive) sputtering method as follows. First, as the sputtering target of the soft magnetic layer 12, a composite body was used in which targets of Cr and Ru were uniformly arranged on a FeTaC alloy target. Ar was used as the discharge gas at that time, the gas pressure was 6 mTorr, and the input RF power was 400 W. Sputtering is performed under these conditions, and the substrate 11
A FeTaCRuCr alloy film was formed on the so as to have a thickness of 5 μm to obtain a soft magnetic layer 12.

Next, a TiN target was used as a sputtering target for the high hardness layer 1. Ar was used as the discharge gas at that time, and the gas pressure was 6 mTorr.
The input RF power was 400W. FeTaCRu obtained as described above was sputtered under these conditions.
A TiN layer having a thickness of 5 nm was formed on the soft magnetic layer 12 of Cr alloy to obtain a high hardness layer 13. The adhesive strength between the high hardness layer 13 and the soft magnetic layer 12 thus obtained has a sufficient value.

Subsequently, the high hardness layer 13 and the soft magnetic layer 12 are formed.
And the laminate was annealed at 590 ° C. for 1 hour. Microcrystals were precipitated in the soft magnetic layer 12 by annealing, and the FeTaCRuCr alloy, which was amorphous before that, became crystalline. The most typical size of the grains (crystal grains) was about 10 nm in diameter. When the composition of the crystalline soft magnetic layer 12 thus obtained was investigated, it was found that Fe ₇₃ Ta ₇ C ₁₀ C
It was r ₇ Ru ₃ .

Most of the grains are α-Fe crystal grains, and the grain size is preferably 1 nm or more and 20 nm or less. The grain size of other crystal grains (for example, TaC) is 10 n
m or less is preferable.

The magnetic characteristics of the soft magnetic thin film 10 obtained as described above were measured. Its saturation magnetic flux density is 1.71 T, coercive force is 0.10 Oe, and relative permeability is 4200 (1 MH
z) and the magnetostriction constant was 5 × 10 ⁻⁷ .

Next, the soft magnetic thin film 10 is heated to room temperature (15
500 ° C in 0.5N sodium chloride solution at ° C)
It was immersed for a time and a corrosion test was performed at room temperature. When the soft magnetic thin film 10 after the immersion was visually observed, no occurrence of corrosion was observed. The magnetic characteristics at this time were the same as those before the test.

On the other hand, this soft magnetic thin film 10 was left in an environment of a temperature of 80 ° C. and a relative humidity (RH) of 95% for 2000 hours or more to perform a corrosion test in a high temperature and high humidity environment. When the soft magnetic thin film 10 after standing was visually observed, no corrosion was observed in this case either. The magnetic characteristics were also the same as before the test.

A scratch test was performed on the surface of the soft magnetic thin film 10, that is, the high hardness layer 13, and it was found that the hardness was higher than that of the surface without the high hardness layer 13 (only the soft magnetic layer 12). It had improved about 7 times. Further, when the friction coefficient of the surface of the high hardness layer 13 was measured, the friction coefficient was (1 /
It was decreasing to 8).

Therefore, the soft magnetic thin film 10 according to the first embodiment.
Was confirmed to maintain the magnetic properties at the beginning of production and also have excellent corrosion resistance.

The annealing step takes into consideration that the step of manufacturing the VTR magnetic head includes a glass bonding step.

In order to prevent the magnetic field strength from decreasing near the surface of the soft magnetic thin film 10, the smaller the thickness of the high hardness layer 13, the better. However, when the thickness is less than 1 nm, sufficient effects of improving corrosion resistance and wear resistance cannot be obtained,
Further, when the thickness exceeds 10 nm, the magnetic field intensity sharply decreases, so it is necessary to set the range from 1 nm to 10 nm. Therefore, the thickness of the high hardness layer 13 is determined by the soft magnetic thin film 1
It may be determined within the above range in consideration of the specifications required for the device to which 0 is applied.

Using the soft magnetic thin film of Example 1, VTR
(Video Tape Recorder) device was made. FIG. 2 shows a schematic configuration of the MIG type magnetic head used for it.
Shows a schematic configuration of the VTR device.

In FIG. 2, the magnetic head 20 comprises two ferrite cores 21 arranged so as to face each other. The soft magnetic thin film 10 of the first embodiment is formed on the facing surfaces of the respective ferrite cores 21 having a substantially V-shaped cross section.
The two ferrite cores 21 are joined and integrated with each other by a lead glass 22 with the soft magnetic thin films 10 facing each other. The two soft magnetic thin films 10 are located in the gap formed by the two ferrite cores 21.

A through hole 23 is formed in the lead glass 22, and one ferrite core 2 is formed by utilizing the through hole 23.
A coil 24 is wound around 1.

Each soft magnetic thin film 10 has a high hardness layer 1 on the surface side.
3 is formed so as to be exposed on the sliding surface of the magnetic head 20. A soft magnetic layer 12 is formed almost entirely on the inside of the sliding surface. On the sliding surface of the magnetic head 20, a recording / reproducing gap G is formed between the opposing soft magnetic thin films 10.

Next, referring to FIG. 3, the magnetic head 20
At the time of recording / reproducing, it is displaced by a magnetic head operating mechanism (not shown) and brought into contact with the magnetic tape T running at a predetermined speed. The magnetic tape T is driven by a magnetic tape drive system (not shown). At the time of recording, the input video signal is first sent to the pre-emphasis 31, and further the FM modulator 32, the recording equalizer 33, the recording amplifier 34.
Is sent to the rotary transformer 35 via. Further, it is transmitted from the rotary transformer 35 to the magnetic head 20 and recorded by the magnetic head 20 on the magnetic tape T running in contact with it.

At the time of reproduction, the video signal recorded on the magnetic tape T is first read by the magnetic head 20 and then transmitted to the rotary transformer 35. Further, from the rotary transformer 35, the reproduction preamplifier 36 and the reproduction equalizer 3 are connected.
7, limiter 38, FM demodulator 39, low-pass filter 40
And the output video signal via the time base collector 41.

Next, the following abrasion resistance test was conducted using this VTR device. The magnetic tape T was run for 3000 hours while maintaining the magnetic head 20 in the state of reproduction, and after the running, the thickness of the TiN high hardness layer 13 on the sliding surface of the magnetic head 20 was measured. As a result, the thickness of the high hardness layer 13 was 5 nm, which was the same as the initial value.

Therefore, it was confirmed that the soft magnetic thin film 10 of Example 1 was also excellent in wear resistance.

Here, the composition of the crystalline soft magnetic layer 12 is Fe ₇₃ Ta ₇ C ₁₀ Cr ₇ Ru ₃ , but the composition is not limited to this, and each element is Ta: 5 to 20 atom%, C 5 to 20. It may be in the atomic% range.

[Embodiment 2] In this embodiment, the soft magnetic second
A CoNbZr alloy film is used as the layer, and a CrN film is used as the high-hardness first layer. The other points are the same as those of the first embodiment (FIG. 1). However, CoNb
The thickness of the soft magnetic layer 12 made of a Zr alloy film is 5 μm, and Cr is
The thickness of the high hardness layer 13 made of the N film is 2 nm.

The soft magnetic thin film having the above structure was formed as follows by using the same sputtering method as that shown in FIG. First, a CoNbZr alloy target was used as a sputtering target for the soft magnetic layer 12. Ar was used as the discharge gas at that time, and the gas pressure was 6 mTo.
rr and input RF power were 400W. Sputtering is performed under these conditions to form a CoNbZr alloy film on the substrate 11 so as to have a thickness of 5 μm.
Got

Next, the high hardness layer 1 was formed on the soft magnetic layer 12 by the ion mixing method. A CrN sintered body was used as a target for ion mixing. Ar was used as the discharge gas at that time, and the gas pressure was 0.5 mTo.
The rr and the acceleration voltage were 600V. CrN under these conditions
I was mixed as described above to obtain C obtained as described above.
A CrN layer having a thickness of 2 nm was formed on the soft magnetic layer 12 of oNbZr alloy to obtain a high hardness layer 13.

The adhesive strength between the high hardness layer 13 and the soft magnetic layer 12 thus obtained has a sufficient value. ◆ At this time, C
At the interface between the oNbZr soft magnetic layer 12 and the CrN high-hardness layer 13, a mixture of CoNbZr and CrN was formed, unlike in Example 1. That is, the interface between the soft magnetic layer 12 and the high hardness layer 13 is not clearly divided, and CoNbZ
There was an intervening layer of a mixture of r and CrN.

Subsequently, the high hardness layer 13 and the soft magnetic layer 12 are formed.
And the laminate was annealed at 590 ° C. for 1 hour. Microcrystals were precipitated in the soft magnetic layer 12 by annealing, and the CoNbZr alloy that was amorphous before then was changed to crystalline.
The most typical size of the grains (crystal grains) was about 10 nm in diameter. When the composition of the crystalline soft magnetic layer 12 thus obtained was investigated, it was Co ₉₂ Nb ₅ Zr ₃ .

Most of the grains are crystal grains of Co, and the grain size is preferably 1 nm or more and 20 nm or less. The grain size of other crystal grains (eg, CoNb alloy) is 1
It is preferably 0 nm or less.

When the magnetic characteristics of this soft magnetic thin film 10 were measured, the saturation magnetic flux density was 1.1 T and the coercive force was 0.10.
Oe, relative permeability is 3200 (1 MHz), magnetostriction constant is 6
It was × 10 ^-7 . Next, as in Example 1, the soft magnetic thin film 10 was immersed in a 0.5 N sodium chloride aqueous solution at room temperature (15 ° C.) for 500 hours, and a corrosion test was performed at room temperature. When the soft magnetic thin film 10 after the immersion was visually observed, no occurrence of corrosion was observed. The magnetic characteristics at this time were the same as those before the test.

Further, this soft magnetic thin film 10 was left in an environment of a temperature of 80 ° C. and a relative humidity (RH) of 95% for 3000 hours or more, and a corrosion test was conducted in a high temperature and high humidity environment. When the soft magnetic thin film 10 after standing was visually observed, neither corrosion nor change in magnetic properties was observed in this case either.

A scratch test was performed on the surface of the soft magnetic thin film 10, that is, the high hardness layer 13, and it was found that the hardness was higher than that of the soft magnetic thin film 10 without the high hardness layer 13 (only the soft magnetic layer 12). It was improved about 5 times. Further, when the friction coefficient of the surface of the high hardness layer 13 was measured, the friction coefficient was (1 /
It was decreasing to 6).

Therefore, the soft magnetic thin film 10 according to the second embodiment is used.
Was confirmed to maintain the magnetic properties at the beginning of production and also have excellent corrosion resistance.

Using the soft magnetic thin film 10 of this Example 2,
A VTR device similar to that of Example 1 (FIGS. 2 and 3) was produced, and the same abrasion resistance test as that of Example 1 was performed. The magnetic tape T was run for 3000 hours while maintaining the magnetic head 20 in the state of reproduction, and after the running, the thickness of the CrN high hardness layer 13 on the sliding surface of the magnetic head 20 was measured. As a result, the thickness of the high hardness layer 13 was 2 nm, which was the same as the initial value.

Therefore, it was confirmed that the soft magnetic thin film 10 of Example 2 was also excellent in abrasion resistance.

In the second embodiment, the CrN film is formed by the ion mixing method as described above, but the dynamic ion mixing method or the ion implantation method may be used. When the dynamic ion mixing method is used, the quality of the CrN film is further improved and becomes denser.
There is also an advantage that it is excellent in adhesiveness with the NbZr film.

In Example 2, CrN was used as the high hardness layer 13.
Although a film is used, the same effect can be obtained by using TaN. Nitride of Mo, W, Zr, Hf, V may be used. Further, those oxides and carbides may be used instead of the nitride.

Here, the composition of the crystalline soft magnetic layer 12 is Co ₉₂ Nb ₅ Zr ₃ , but the composition is not limited to this, and each element is in the range of Nb: 5 to 20 atom%, Zr 5 to 20 atom%. It should be inside.

In Examples 1 and 2, the FeTaCRuCr alloy film and CoNbZr were used as the soft magnetic layers, respectively.
Although an alloy film is used and a TiN film and a CrN film are used as the high hardness layer, the present invention is not limited to these. Any soft magnetic layer can be used as the soft magnetic layer, and any non-magnetic layer having a higher hardness than the soft magnetic layer can be used as the high hardness layer. .

Although the soft magnetic thin film of the present invention is applied to a magnetic head for a VTR device, the present invention is not limited to this and can be applied to a magnetic head of any other magnetic recording device.

[0069]

According to the soft magnetic thin film of the present invention, it is possible to improve corrosion resistance and wear resistance while maintaining optimized magnetic characteristics.

According to the magnetic head and the magnetic recording apparatus of the present invention, excellent durability and high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a soft magnetic thin film according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of an MIG type magnetic head according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a VTR device according to an embodiment of the present invention.

[Explanation of symbols]

 10 Soft Magnetic Thin Film 11 Substrate 12 Soft Magnetic Layer 13 High Hardness Layer 20 Magnetic Head 21 Ferrite Core 22 Lead Glass 23 Through Hole 24 Coil G Gap 31 Pre-Emphasis 32 FM Modulator 33 Recording Equalizer 34 Recording Amplifier 35 Rotation Transformer 36 Playback Preamplifier 37 Reproduction equalizer 38 Limiter 39 FM demodulator 40 Low-pass filter 41 Time base collector T Magnetic tape

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

Claims (13)

[Claims] 1. A non-magnetic first layer disposed on the surface side,
A soft magnetic thin film, comprising: a soft magnetic second layer disposed inside and adjacent to the first layer, wherein the hardness of the first layer is higher than the hardness of the second layer. 2. The first layer comprises Ti, Ta, Cr, M
formed of a compound of at least one element selected from the group consisting of o, W, Zr, Hf and V, or a mixture thereof, and the compound is at least one of nitride, carbide and oxide of the element. The soft magnetic thin film according to claim 1, which is of a type. 3. The soft magnetic thin film according to claim 1, wherein the second layer is formed of a soft magnetic layer containing Fe as a main component and further containing Ta and C. 4. The soft magnetic thin film according to claim 3, wherein the first layer is a TiN layer. 5. The soft magnetic thin film according to claim 1, wherein the second layer is formed of a soft magnetic layer containing Co as a main component and further containing Nb and Zr. 6. The soft magnetic thin film according to claim 5, wherein the first layer is formed of a CrN layer. 7. The thickness of the first layer is 1 nm or more and 10 n.
The soft magnetic thin film according to any one of claims 1 to 6, which has a thickness of m or less. 8. The method according to claim 1, wherein the first layer is formed on the second layer by any one of a sputtering method, an ion plating method and an ion mixing method. The soft magnetic thin film described. 9. The soft magnetic thin film according to claim 1, wherein the first layer is partially formed on one side of the second layer. 10. A magnetic head comprising the soft magnetic thin film according to claim 1. Description: 11. The magnetic head according to claim 10, wherein the soft magnetic thin film is arranged in a gap formed in the core. 12. The first layer of the soft magnetic thin film is arranged in contact with a moving magnetic recording medium.
The magnetic head according to 0 or 11. 13. A magnetic recording apparatus comprising the magnetic head according to claim 10.