JPH07283028A - Soft magnetic thin film, magnetic head and recorder employing it - Google Patents

Abstract

PURPOSE:To obtain a microcrystal deposition soft magnetic thin film having high heat resistance by providing a layer for controlling the growth of crystal particle in the vicinity of interface between the magnetic film and a substrate having or not having a surface layer. CONSTITUTION:A thin amorphous film is deposited on a crystalline substrate and subjected to heat treatment thus obtaining an amorphous soft magnetic thin film of 30-50mum thick. Crystal growth in the magnetic thin film due to heat treatment is controlled by heat treating the amorphous thin film deposited on the crystalline substrate and forming a thin film exhibiting soft magnetic characteristics through heat treatment. In this regard, formation of columnar texture is retarded. The amorphous thin film is formed of at least one metal selected from Cr, Al, Ni, Zr, Ti, Ta, Nb, and Co or an alloy thereof.

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 having soft magnetic characteristics, and particularly to a structure of a soft magnetic thin film and a magnetic film having high performance and high reliability, and a magnetic film produced using the same. The present invention relates to a head and a magnetic recording device.

[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. Among them, studies on high-density recording and downsizing of magnetic recording devices are being rapidly advanced. A medium having a high coercive force and a high-performance magnetic head capable of recording on this medium are required in order to allow the recorded minute magnetic domains to exist stably and to realize high density recording. In order to sufficiently magnetize the high coercive force medium to record a signal, a magnetic head material having a high saturation magnetic flux density capable of generating a strong magnetic field is required.

At present, Fe-C type and Fe-N type materials are known as materials having a high saturation magnetic flux density proposed. These materials exhibit soft magnetic properties by being heat-treated after film formation and crystallized. However, using these materials for magnetic heads,
When forming a gap (MIG) type head, it is necessary to secure thermal stability because the head manufacturing process includes a heat treatment process. The heat treatment temperature is determined by the temperature at the time of glass bonding in the head manufacturing process. Therefore, the magnetic film must have thermal stability above a certain temperature.

Further, since Fe--C type and Fe--N type materials are mainly composed of Fe, they react with oxygen and water in the atmosphere to form hydroxides and oxides, resulting in magnetic characteristics, In particular,
Since the coercive force and the saturation magnetic flux density fluctuate, the performance of the magnetic head may deteriorate. Therefore, in putting a magnetic head using this material into practical use, it was also an object to suppress the fluctuation of these magnetic characteristics. In order to solve these problems, it has been proposed to add an element for improving corrosion resistance in addition to the magnetic element. As a known example thereof, Japanese Patent Laid-Open No. 3-20444 can be cited.

[0005]

For example, when a MIG type head is formed using a soft magnetic film, a bonding step using an adhesive such as glass is included, and therefore the magnetic film has a soft magnetic property even after this step. It is practically necessary to suppress the deterioration of. However, in the above-mentioned publicly known examples, this point has not always been fully taken into consideration. Furthermore, iron group-metalloid magnetic materials typified by Fe-C-based and Fe-N-based materials do not have practically sufficient resistance to corrosion, so that magnetic characteristics can be ensured. Both of ensuring corrosion resistance must be satisfied at the same time.

[0006] The above-mentioned publicly known example is intended to achieve both improvement of magnetic properties and corrosion resistance by optimizing additive elements. However, if the corrosion resistance is to be ensured, the magnetic characteristics, especially the saturation magnetic flux density and the coercive force are deteriorated, and the performance of the magnetic head is deteriorated. as a result,
When magnetic recording is performed by a magnetic recording device using this head, an error or noise may occur. Further, when trying to secure the magnetic characteristics, the resistance to water and oxygen in the environment is not always sufficient, and the magnetic characteristics change due to corrosion of the magnetic film, which may cause errors and noise.

An object of the present invention is to provide an iron group element having a high saturation magnetic flux density, in particular, a magnetic film mainly composed of Fe or Co and having a soft magnetic property, which is excellent in thermal stability and further,
It is to provide a magnetic material having excellent soft magnetic characteristics and corrosion resistance. A second object of the present invention is to provide a high performance magnetic head using a magnetic material having a high saturation magnetic flux density for a magnetic film. Further, a third object of the present invention is to provide a high performance magnetic recording device which can improve the recording density by constructing a magnetic recording device using this high performance magnetic head. A fourth object of the present invention is to provide a soft magnetic film having high reliability and high performance in a magnetic film mainly having an iron group element having a high saturation magnetic flux density and having soft magnetic characteristics, and a magnetic head using the same. , To provide a magnetic recording device.

[0008]

In order to achieve the above object, when a metal thin film having soft magnetic characteristics is formed on a substrate having crystallinity, an amorphous thin film is formed on the substrate to a certain thickness. After forming the thin film, the magnetic thin film is formed. Here, the film thickness of this thin film is 3 nm or more and 50 nm.
The following is preferable. More importantly, after the magnetic film is formed, the amorphous thin film formed earlier does not react with or diffuse into the magnetic thin film formed subsequently by the heat treatment for developing the soft magnetic property. It is preferable.

The amorphous thin film has the effect of suppressing the crystal growth reaction of the magnetic film formed by sputtering, particularly the growth reaction of the columnar structure formed at both interfaces of the magnetic film or at one of the interfaces. The material and the film thickness are desirable. When a columnar structure is formed, soft magnetic properties, especially,
The coercive force is increased, making it unsuitable as a material for magnetic heads. This is because deterioration of soft magnetic properties, especially coercive force properties,
This is because the crystallite size of the soft magnetic thin film that precipitates is a certain size or more.

The amorphous thin film formed on the crystalline substrate is a metal or an alloy. More advantageously, the metal is one of Cr, Al, Ni, Zr, Ti, Ta, Nb and Co. It is preferable to use at least one selected element or its alloy. Effective alloys are, for example, amorphous Co-Ta-Zr system, Co-Nb-
Zr system is one example. The amorphous thin film formed on the substrate is an inorganic compound other than a metal material, and more advantageously, the inorganic compound is silicon nitride, silicon oxide, aluminum nitride, chromium oxide, titanium nitride, tantalum nitride. , At least one compound selected from titanium oxide, tantalum oxide, and aluminum oxide may be used. In particular, in the case of these materials, the diffusion into the magnetic film is unlikely to occur, and since few materials become crystal nuclei, it is difficult to form a columnar structure.

As a specific material of the metal thin film having soft magnetic characteristics, Fe or Co and Ta of 5 at% to 20 are used.
In the concentration range of at%, at least one element selected from Si, B, C, and N in the concentration range of 1 at% to 20 at% is mainly contained in the magnetic film.
Ti, Cr, Nb, Ru, Rh, Pt, Pd, Mo, W
A material in which at least one element selected from the above is added at a concentration of 1 at% or more and 20 at% or less is preferable. Here, as an element to be added to the soft magnetic film, an alloy thin film containing a plurality of kinds of elements having different free energies of reaction with carbon and different solid solution rates to Fe is heat-treated to precipitate fine crystals, An element having a large free energy of reaction with carbon and a small solid solution rate to Fe is precipitated at the grain boundary, and an element having a small free energy of reaction with carbon and a large solid solution rate to Fe is added to Fe. It is preferably present as an alloy in the microcrystalline phase.

By heat-treating these soft magnetic thin films, at least one selected from the intermetallic compounds and / or metal carbides, nitrides, or borides between the α-Fe phase and / or this Fe. A microcrystalline thin film composed of two compound phases is formed. In this case, what is important is that the crystal grain size of each phase of the soft magnetic thin film after heat treatment at least at 700 ° C. is 1 nm or more and 20 nm or less for the intermetallic compound between α-Fe phase or Fe, carbide,
At least one compound phase selected from the group consisting of nitrides and borides is preferably 1 nm or more and 10 nm or less. Further, it is preferable that the crystal orientation is changed or microcrystallized, and it is further preferable that the α-Fe phase has a maximum of 10 nm and the TaC layer has a thickness of 5 nm or less.

It is preferable to use this soft magnetic thin film as a magnetic film of a magnetic head. Most preferably, the magnetic head is a metal-in-gap type. Further, it is preferable to configure a magnetic recording device using this magnetic head. Then, it is effective that the information is recorded using this device, and more preferably that the information is image information or audio information. Then, the information is recorded on the moving information recording medium by using the above magnetic head by the magnetic property. As the moving information recording medium used, any magnetic recording medium having an easy axis of magnetization in the direction parallel to or perpendicular to the substrate may be used.

[0014]

According to the above means, the amorphous thin film is formed on the crystalline substrate, and then the magnetic film is formed, so that the heat treatment for forming the magnetic film and performing the heat treatment for exhibiting the soft magnetic characteristics is performed. It is possible to suppress the generation or growth of the columnar structure formed by the crystal precipitation reaction. This is the substrate surface that is formed by forming an amorphous thin film on a crystalline substrate (usually a crystal layer is formed at the beginning of film formation) and the subsequent microcrystal precipitation reaction. This is because the existence of points that serve as nuclei for crystallization of (1) is extremely small, and thus the generation and growth of columnar structures are suppressed. As a result, the crystal growth reaction can be suppressed, and the heat resistance of the magnetic film can be improved. Such an action is sufficient as long as an amorphous film is formed on the crystalline substrate, and the material may be either a metal or an inorganic compound, and an inorganic compound which is difficult to diffuse is particularly preferable.

[0015]

【Example】

(Example 1) In this example, FeTaC was used as the soft magnetic thin film.
This is an example using a CrNb alloy film. The magnetic film is prepared by depositing a Si ₃ N ₄ film on a ferrite single crystal substrate at 10Å to 500Å.
And the film thickness was changed. Following that, FeTa
A CCrNb soft magnetic thin film was used. The magnetic film was formed by using the sputtering method. The target of spatter is F
The powder of each element of e, Ta, C, Nb, and Cr was molded by the hot isostatic pressing method (HIP method). The impurity oxygen concentration in this target was 400 ppm or less. The composition of the target is Fe ₇₃ Ta ₇ C ₈ Cr ₇ Nb ₅ ,
The composition of the obtained film was almost the same as that of the target even if the film was thinned. The respective characteristics of the magnetic film at that time are that the saturation magnetic flux density is 1.5 T, the coercive force is 0.2 Oe, the magnetic permeability at 1 MHz is 3000 or more, and the magnetostriction constant is 7 ×.
It was 10 ^-7 . Sputtering was performed on the substrate using the above alloy target and Ar as the discharge gas. The sputtering conditions are: discharge gas pressure: 5 mTorr, input RF power: 400 W. These sputtering conditions depend on the sputtering device and the like, and are not limited to these values. The thickness of the magnetic film thus formed is 5
μm.

FIG. 1 shows the heat treatment temperature dependence of the coercive force when the magnetic film is heat treated at various temperatures. This is because the change in coercive force reflects the crystal grain size of the magnetic film. It can be seen that the coercive force of this FeTaCCrNb alloy film does not depend on the heat treatment temperature even when heat-treated from 500 ° C. to 700 ° C.

When the film thickness dependence of the silicon nitride film is examined, as shown in FIG. 2, the coercive force is almost constant when the film thickness is 30 Å or more, and when the film thickness is 500 Å or more, the magnetic film is removed from the substrate. Peeled off. From this result, the effective film thickness of the amorphous layer is between 30Å and 500Å. When the heat treatment is performed, the amorphous film immediately after the film formation is crystallized, so that soft magnetic characteristics are exhibited. When the film structure of the soft magnetic film heat-treated at 700 ° C. was observed with a transmission electron microscope, the Fe phase crystal size was between 8 nm and 16 nm,
The average was 10 nm. The crystal size of the TaC phase was between 4 nm and 6 nm. When the lattice constant was calculated from the result of X-ray diffraction, the Fe phase was larger than α-Fe. Therefore, FeCrNb alloy, FeNb alloy or FeC was obtained.
It is considered to be an alloy such as r alloy and it is understood that a solid solution is formed. Further, when the cross-sectional structure of this magnetic film was observed with a transmission electron microscope, when the magnetic film was directly formed on the crystalline substrate, a columnar structure portion was present at the interface between the substrate and the magnetic film. On the other hand, when the silicon nitride layer was provided with a film thickness of 30 Å or more, no columnar structure layer was present.

The magnetic film heat-treated at 700 ° C. was immersed in a 0.5N sodium chloride aqueous solution for 500 hours. As a result, no occurrence of corrosion was observed by visual observation. In addition, as a result of measuring the magnetic characteristics after immersion for 500 hours, no difference was observed from the characteristics immediately after film formation.
Further, when this magnetic film was allowed to stand in an environment of 80 ° C. and 95% RH for 2000 hours or more, no occurrence of corrosion or change in magnetic properties was observed. As described above, if the size of the crystal grains at the time of precipitation was large, they were susceptible to corrosion. In this way, controlling the crystallite precipitation reaction (crystal grain size or F
By separating two layers of e and TaC), a magnetic film having high corrosion resistance could be obtained.

Using this film, a MIG (metal in gap) type head was produced. The perspective view is shown in FIG.
The magnetic head was manufactured by forming the soft magnetic thin film 1 on a single crystal ferrite substrate 2 with a silicon nitride film interposed therebetween with a thickness of 50 Å. The gap 3 was formed by forming SiO ₂ to a thickness of 200 nm and then Cr to a thickness of 100 nm on the soft magnetic thin film 1 formed on the ferrite substrate 2. This was heat-treated in a nitrogen stream at 600 ° C. for 1 hour, and head substrates of the same shape were bonded with the low melting point glass 4.
Here, the heat treatment temperature is controlled by the temperature in this glass bonding step. A bonding layer may be provided between the substrate and the magnetic film to improve the adhesiveness between them.

Using this magnetic head, a VTR device was produced and a tape was run to record image information. High-definition digital information recorded, S / N is 40
It was dB. Here, the relative speed is 36 m / s, the data rate is 46.1 Mbps, and the track width is 40 μm.

The corrosion resistance of this head was evaluated by the immersion test method in a 0.5N sodium chloride aqueous solution and the condensation test method in a high temperature and high humidity environment (60 ° C., relative humidity: 95%). First, the head chip was immersed in a 0.5N sodium chloride aqueous solution for 1000 hours. After that, the head was set again in the apparatus and the recording / reproducing characteristics were measured. As a result, no difference was observed in the recording / reproducing characteristics before immersion. In addition, high temperature and high humidity environment (60 ℃,
The relative humidity: 95%) In the evaluation by the dew condensation test method, the MIG head was fixed on the Peltier element and kept at 10 ° C., and the Peltier element was maintained at 60 ° C., relative humidity: 9
It was left in a 5% environment. Condensation occurred on the entire head.
I left it in this environment for more than 2000 hours in this state,
No occurrence of corrosion or deterioration of recording or reproduction signal was observed.
Up to now, the magnetic head for VTR has been described as an example,
The effect of the present invention can be applied to a magnetic disk device or a magnetic tape device using a helical scan, and does not depend on the device or the like.

Further, the above is the case where the FeTaCNbCr alloy film is used for the magnetic film, but the effect of the present invention is not limited to this material system, and at least in addition to C, B, S
The same applies when a magnetic film is formed using i, N, or the like. In addition to improving thermal stability, it is possible to improve the corrosion resistance of the magnetic film while maintaining high-performance soft magnetic characteristics. Further, as elements to be added, in addition to Nb and Cr, Al and T
The same effect can be obtained in a magnetic film to which one or two elements selected from i, Cr, Nb, Ru, Rh, Pt, Pd, Mo and W are added. Here, even when B, N, Si or the like other than C is used, each compound (boride, silicide, nitride, etc.) is used similarly to C.
Is formed. It is considered that the action of these additional elements is because the growth of crystal grains is suppressed by precipitating as a compound at the crystal grain boundary and / or forming an alloy such as an intermetallic compound.

Further, the magnetic film is made of Cr, Al, Ni, Z.
It may be formed through a film of at least one element selected from r, Ti, Ta, Nb, and Co, or an alloy thereof. In addition to SiNx, it is an inorganic compound as an amorphous thin film, and the inorganic compound is selected from among silicon oxide, aluminum nitride, chromium oxide, titanium nitride, tantalum nitride, titanium oxide, tantalum oxide, and aluminum oxide. Similar effects can be obtained by using at least one selected compound.

[0024]

According to the present invention, in a microcrystalline precipitation type soft magnetic thin film, a control layer having an effect of suppressing crystal grain growth is provided near the interface between the magnetic film and the substrate or the substrate having the surface layer. This suppresses the growth of crystal grains.
As a result, a soft magnetic thin film having high heat resistance can be obtained, and MI
Even in the processing step of the G-type head, processing at high temperature such as glass bonding can be performed, the strength of the head is increased, and the reliability of the head can be improved while maintaining high performance. Further, the growth of the crystal grains is suppressed and the crystal orientation is changed, so that the corrosion resistance of the magnetic film is improved and the life of the head is improved.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a heat treatment temperature and a coercive force.

FIG. 2 is a characteristic diagram showing the relationship between the thickness of an amorphous layer and coercive force.

FIG. 3 is a perspective view showing the structure of a metal-in-gap type magnetic head.

[Explanation of symbols]

1 ... Soft magnetic thin film, 2 ... Ferrite substrate, 3 ... Gap part, 4 ... Low melting point glass part.

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

Claims (16)

[Claims] 1. A magnetic thin film exhibiting soft magnetic characteristics is formed by heat treatment after forming an amorphous thin film on a crystalline substrate. Advantageously, the film thickness of the amorphous thin film is Is 3 nm or more and 50 nm or less, a soft magnetic thin film. 2. A crystal growth reaction of the magnetic thin film is controlled by the heat treatment by forming an amorphous thin film on a crystalline substrate and then performing a heat treatment to form a magnetic thin film exhibiting soft magnetic characteristics. And a method for manufacturing a soft magnetic thin film. 3. A method for producing a soft magnetic thin film in which the formation of a columnar structure is suppressed as the controlled crystal growth reaction according to claim 2. 4. The amorphous thin film formed on the substrate according to claim 1, which is a metal or an alloy, and more advantageously,
The metal is Cr, Al, Ni, Zr, Ti, Ta, N
A soft magnetic thin film using an amorphous thin film made of at least one element selected from b and Co or an alloy thereof. 5. The amorphous thin film formed on the substrate according to claim 1, which is an inorganic compound, and more advantageously, the inorganic compound is silicon nitride, silicon oxide, aluminum nitride, chromium oxide, Titanium nitride, tantalum nitride,
A soft magnetic thin film using an amorphous thin film made of at least one compound selected from titanium oxide, tantalum oxide, and aluminum oxide. 6. A soft magnetic thin film in which an element of an amorphous thin film formed on a crystalline substrate according to claim 1 does not diffuse into a magnetic thin film exhibiting soft magnetic characteristics by subsequent heat treatment. . 7. A magnetic film exhibiting soft magnetic characteristics by performing at least the heat treatment according to claim 1, wherein Fe or Co is added to Ta in a concentration range of 5 at% to 20 at%. Al, Ti, Cr, N in the magnetic film mainly containing an element containing at least one kind of element selected from the above in a concentration range of 1 at% to 20 at%.
b, Ru, Rh, Pt, Pd, Mo, W, at least one element selected from 1 at% or more and 20 at
Soft magnetic thin film added at a concentration of less than or equal to%. 8. The element added to the soft magnetic film according to claim 7 has a different free energy of reaction with carbon and Fe.
An alloy thin film containing a plurality of elements with different solid solution rates is heat-treated to precipitate fine crystals, and the free energy of the reaction with carbon at the grain boundaries is large, and the element with a small solid solution rate to Fe is added. Precipitation and small free energy of reaction with carbon F
A soft magnetic thin film in which an element having a higher solid solution rate in e is present as an alloy in the Fe microcrystalline phase. 9. Deterioration of the soft magnetic properties of the magnetic film, especially coercive force, even when the soft magnetic thin film according to claim 1, 2, 3, 4, 5, 6, 7 or 8 is heated to 700 ° C. or higher. A soft magnetic thin film that suppresses deterioration. 10. Claims 1, 2, 3, 4, 5, 6, 7, 8
Alternatively, a soft magnetic thin film in which the film thickness of the amorphous layer formed prior to the formation of the magnetic film according to 9 is 3 nm or more and 30 nm or less. 11. Claims 1, 2, 3, 4, 5, 6, 7,
In the soft magnetic thin film described in 8, 9, or 10, at least at a temperature of 700 ° C., the film thickness of a portion having a columnar structure at least near the interface of the magnetic film on the substrate side and / or the interface on the opposite side is at least A soft magnetic thin film that is 5% or less of the thickness of the magnetic film. 12. Claims 1, 2, 3, 4, 5, 6, 7,
A magnetic head using the soft magnetic thin film described in 8, 9, 10 or 11. 13. A magnetic head according to claim 12, which is a metal-in-gap type. 14. A magnetic recording device using the magnetic head according to claim 12. 15. A magnetic recording device in which information is recorded by a magnetic property by using the magnetic head according to claim 12. 16. A magnetic recording apparatus according to claim 14 or 15, wherein the moving information recording medium is a magnetic recording medium having an easy axis of magnetization in a direction parallel or perpendicular to the substrate.