JPH1097910A - Micro-crystallized magnetic thin film and magnetic head and magnetic recorder using the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously improve soft magnetic characteristics, heat stability and corrosion resistance. SOLUTION: A magnetic thin film contains at least Hf and N and the rest is composed of Fe. The film has a polycrystal structure having at least Fe crystal grains, and compound particles of Hf and N or in addition, Hf metal. The composition ratio of Hf and N is 1.2-1.7 and the film has a soft magnetic property. The film has a high saturation magnetic flux density of Bs>=1.5T or more and exhibits excellent soft magnetic characteristics. The film also exhibits high heat stability and high corrosion resistance as soft magnetic thin film. Thus, a high performance and highly reliable magnetic head and a magnetic recorder using the magnetic head can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcrystalline precipitation type Fe-based soft magnetic thin film having a high saturation magnetic flux density.
The present invention relates to a soft magnetic thin film having high performance and high reliability, and a magnetic head and a magnetic recording device manufactured using the magnetic film.

[0002]

2. Description of the Related Art With the recent development of a highly information-oriented society, there is an increasing need for a small and high-density information storage device. Among them, magnetic recording devices are used for high-density recording,
Research into downsizing is rapidly advancing. In order to realize high-density recording, a medium having a high coercive force so that recorded magnetic domains are stably present and a high-performance magnetic head capable of recording on this medium are required. In order to record a signal by sufficiently magnetizing a high coercivity medium, a magnetic head material having a high saturation magnetic flux density capable of generating a strong magnetic field is required. At present, the proposed materials having a high saturation magnetic flux density include Fe-C and Fe-N materials. These materials are heat-treated at a certain temperature in order to develop soft magnetic characteristics. The heat treatment temperature is determined by a temperature (crystallization temperature) required to develop soft magnetic characteristics. This temperature depends on the material system used and its composition. In addition, when manufacturing a magnetic head using this material, especially when the head is a metal-in-gap (MIG) type head, a glass bonding step is included in the head manufacturing process. Annealing is required. The bonding temperature in that case is determined by the material of the welding glass used. This temperature is determined by the melting temperature of the deposited glass, and generally the bonding temperature is usually higher than the crystallization temperature. This is because when the bonding temperature is high, the strength of the glass is excellent, and when the temperature is low, the glass does not have sufficient strength. For this reason, in the case of a commonly used glass, the temperature is often higher than the temperature at which the soft magnetic characteristics are exhibited. as a result,
The magnetic film must have thermal stability to withstand at least the melting temperature of the glass. In particular, since the soft magnetic properties depend on the size of the precipitated microcrystalline particles, in order to obtain a magnetic film having good soft magnetic properties,
This crystal grain size must be controlled.

Further, since these materials are mainly composed of Fe, they react with oxygen and water in the atmosphere to form hydroxides and oxides, and have a magnetic property, particularly a coercive force and a saturation magnetic flux density. Due to the fluctuation, the performance of the magnetic head was sometimes reduced. Therefore, in putting a magnetic head using this material into practical use, fluctuations in magnetic characteristics due to corrosion when the magnetic film is left in an environment of use are suppressed, and fluctuations in magnetic characteristics are suppressed even after a glass bonding process. The problem was to get rid of it.

[0004] In order to solve these problems, it has been proposed to add an element for improving corrosion resistance in addition to the magnetic element. In that case, it was difficult to achieve both soft magnetic properties and corrosion resistance. As a publicly known example in which these points are examined, Japanese Patent Application Laid-Open No. 03-20444 can be mentioned.

[0005]

The above-mentioned prior art discloses an effective method for improving any one of the soft magnetic characteristics, the thermal stability, and the corrosion resistance. . However, a method for simultaneously improving these characteristics has not been sufficiently disclosed. In particular, it can be said that there is no soft magnetic film having a saturation magnetic flux density of 1.5 T or more.

Accordingly, an object of the present invention is to provide a magnetic thin film having good soft magnetic characteristics in a high frequency range, high thermal stability, and high reliability.

[0007]

The object of the present invention is to provide a microcrystalline precipitation type Fe-based magnetic thin film in which at least Hf and N are contained and the balance is made of Fe. More specifically, the magnetic thin film includes at least Fe crystal grains. Having a polycrystalline structure containing only Hf and N compound particles or a Hf metal in addition thereto, and the composition ratio of the Hf and N compound particles being 1.2 or more and 1.7 or less Can be realized by: Further, the magnetic thin film preferably has soft magnetic characteristics. More specifically, the compound particles of Hf and N are Hf ₄ N ₃ , Hf
₃ N it is good at least one compound selected from among _2. It goes without saying that a mixture of two kinds or an indefinite non-compound may be used. In the stoichiometric compound, Hf and N
Hf ₄ N ₃ or Hf ₃ N ₂ , which is a compound particle of the above, usually deviates from the stoichiometric composition in the production, and the deviation is preferably ± 10%. As a result, in the obtained microcrystalline precipitation-type Fe-based magnetic thin film containing at least Hf and N and the balance being Fe, the size of the Fe crystal particles is 15 nm or less, and the Hf and N compound particles are used. Is preferably 3 nm or less from the viewpoint of magnetic properties and corrosion resistance. In the microcrystalline precipitation type Fe-based magnetic thin film, among the Hf components, metal Hf is precipitated as a crystal phase, or is precipitated at a crystal grain boundary of Fe, or both are present simultaneously. Is either. Also,
As for one part of nitrogen, one part of N is dissolved in Fe, and more advantageously, one part of N dissolved in Fe forms a compound with Fe. It is preferable from the viewpoint of magnetic properties and corrosion resistance. The magnetic properties of the soft magnetic film produced in this manner are such that the saturation magnetic flux density is 1.5 T or more and the coercive force is 1
Oe or less, and the magnetic permeability at 50 MHz is 1000 or more.

The composition of the magnetic film is such that in a microcrystalline precipitation type Fe-based magnetic thin film containing at least Hf and N and the balance being Fe, the composition of the magnetic thin film is such that the total of Hf and N is 15 at% or less.
It is preferable that the ratio of Hf to N: [Hf] / [N] be in the range of 0.5 to 1.5 in terms of magnetic properties and corrosion resistance.

It is most preferable to use the above-mentioned magnetic film as a soft magnetic film for a magnetic head. In particular, as a magnetic head using the above soft magnetic thin film, metal-in-
A gap type magnetic head is most preferable. Further, this magnetic head is most suitable for recording information on a moving information recording medium using magnetic properties. Most preferably, the information to be recorded is image information and / or audio information. It is most preferable to use a magnetic recording medium layer formed on a tape or a disk as a moving information recording medium.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to embodiments. A magnetic thin film was prepared by a sputtering method. The target used was a composite target in which Hf chips were uniformly arranged on a Fe disk, and the discharge gas was Ar / N
_Two standard mixed gases (mixing ratio: 92/8) were used respectively. A Mn / Zn ferrite substrate was used as the substrate. Crystal orientation is (332)
The plane and substrate position are # 4. The substrate is not limited to this, and the effect of the present invention does not depend on the type. The sputtering conditions are as follows: discharge gas pressure is 6 mTorr, input R
F Power density is 400 W / 150mmφ. The thickness of the formed magnetic thin film is 2 μm. According to EDX analysis, the composition of this magnetic film is Fe ₇₇ Hf ₉ N ₁₄ . 600 magnetic films after film formation
Heat treatment was performed at 30 ° C. for 30 minutes. This temperature is determined by the composition and structure of the magnetic film, and is not absolute.

The magnetic characteristics of the magnetic thin film were measured. The saturation magnetic flux density was 1.55 T, the coercive force was 0.10 Oe, and the magnetic permeability was 7500 at 1 MHz and 1800 at 50 MHz. Magnetostriction constant was 4 × 10 ~ ^7. The specific resistance was 95.8 × 10 to ⁸ (Ω · m).

The corrosion resistance of the magnetic film was evaluated by the change over time of the saturation magnetic flux density when the magnetic thin film was immersed in 0.5N NaClaq. As a result, no deterioration of the saturation magnetic flux density was observed after immersion for 200 hours. Further, for comparison, the results of examining the magnetic properties and corrosion resistance of the magnetic thin film when the [Hf] / [N] ratio and the total concentration of Hf and N in the magnetic film were changed are shown in FIG. . From the top of this figure, [Hf] /
It can be seen that the corrosion resistance is deteriorated even if the [N] ratio is larger than 1.5 or smaller than 0.5. From this result, it can be seen that the composition range is between 0.5 and 1.5, but is a suitable composition. Regarding the relationship between the total concentration of Hf and N and the corrosion resistance, the lower the concentration, the higher the saturation magnetic flux density.However, if the concentration is less than 15 at%, the film is crystallized in the early stage of film formation. Is more than 10 Oe,
It can be seen that it is not suitable as a magnetic film for a magnetic head. Conversely, if the total concentration exceeds 25 at%, the soft magnetic characteristics do not deteriorate, but the saturation magnetic flux density becomes smaller than 1.5 T, making the magnetic head unsuitable for high-density recording magnetic heads. From the above examination, the total concentration was 15 at% or more and 25 at%
The following concentrations are suitable: To summarize what we have studied so far, the (Hf) / [N] ratio is 0.5 ≦ [Hf] / [N] ≦ 1.5
Is good, and the total concentration of Hf and N ((Hf) + (N)) is 15 ≦
It is understood that the range of ([Hf] + [N]) ≦ 25 is preferable.

Next, the above-mentioned magnetic properties and corrosion resistance are excellent.
The structure of the Fe ₇₇ Hf ₉ N ₁₄ magnetic thin film was analyzed using a transmission electron microscope. The result is shown in FIG. In this figure, based on the observation result of the lattice image of Fe ₇₇ Hf ₉ N ₁₄ , the lattice image was analyzed using the fact that the lattice image and electron diffraction The result of examining the correspondence is shown. According to this, the size of Fe crystal grains is almost 8 nm, and Fe-Ta
The distribution is smaller than the 8 nm to 15 nm of the -C film, and the crystal grain size is also small. The Hf-N crystal particles have a size of 2 nm, and the Fe-Ta-C film
It can be seen that the Fe-Hf-N system makes the Hf-N particles finer than the 3 nm to 5 nm particles. Compounds of Hf-N system are formed at this time, the lattice spacing obtained from the results of electron diffraction, Hf, Hf ₄ N _3, or it can be seen that the Hf ₃ N ₂ is formed. Further, when a part of Hf was analyzed by micro Auger spectroscopy, it was found that it precipitated at the grain boundaries of Fe crystal particles and suppressed the growth of the Fe crystal phase. Then, in this Fe-Hf-N 2 system, the Hf-N particle size and the stoichiometric ratio were changed by changing the heat treatment conditions after film formation and the nitrogen concentration during film formation. According to this, when the Hf-N particle size was not changed and the stoichiometric ratio of Hf and N was changed to HfN, the magnetic properties did not change, but the NaC
As a result of laq immersion test, when the saturation magnetic flux density was immersed for 200 hours,
Approximately 15% of the initial value decreased, and the corrosion resistance deteriorated. When the nitrogen concentration was lowered and the [Hf] / [N] ratio was made larger than 1.7 (Hf-rich), the magnetic properties deteriorated. This is because the crystallization reaction has not sufficiently occurred. From this, Hf
The [Hf] / [N] ratio of the -N compound is suitably between 1.2 and 1.7. Further, the crystal grain size of Fe is preferably 5 nm or more in terms of magnetic properties, preferably 20 nm, and 1 mm in terms of corrosion resistance.
It is preferably 5 nm or less, and from this result, a good Fe crystal particle size needs to be in the range of 5 nm to 15 nm.

An MIG (metal-in-gap) head was manufactured using the above magnetic film. FIG. 3 is a schematic diagram showing the structure. In manufacturing the magnetic head, the soft magnetic thin film (1) was formed on a single crystal ferrite substrate (2). Here, the composition of the magnetic film used, a Fe ₈₀ Hf ₈ N _12. Gap part
(3) is the soft magnetic thin film formed on the ferrite substrate (2).
(1) After forming SiO ₂ to a thickness of 200 nm on top, Cr
Was formed. This is heat-treated at 600 ° C for 30 minutes in a nitrogen stream, and a head substrate of the same shape is made of low-melting glass (4).
Bonding. Here, the heat treatment temperature is governed by the physical properties of the glass such as the glass fusing temperature in the glass bonding step, and is not limited to this temperature. Further, a bonding layer may be provided between the substrate and the magnetic film for improving the adhesion between the two. If the underlayer has magnetism, the performance of the magnetic head can be further improved. No film peeling or the like occurred in the magnetic head thus manufactured.

Using this magnetic head, a VTR device was manufactured, and a tape was run to record image information. When the digital information of HDTV was recorded, the S / N was more than 40dB. Here, the relative speed is 36 m / s, the data transfer rate is 46.1 Mbps, and the track width is 40 μm. The corrosion resistance of this head was measured by immersion test method in 0.5N sodium chloride aqueous solution, and high temperature and high humidity environment (60 ° C, relative humidity: 95
%) By the dew condensation test method. First, the MIG type head chip was immersed in a 0.5 N aqueous sodium chloride solution for 500 hours. Thereafter, the head was set in the apparatus again, and the recording / reproducing characteristics were measured. As a result, no difference was observed in the recording / reproducing characteristics from before the immersion. In addition, the evaluation by the dew condensation test method in a high-temperature and high-humidity environment (60 ° C, relative humidity: 95%) was performed by fixing the above MIG head on a Peltier element and maintaining the temperature at 10 ° C. : 95% left in the environment. As a result, dew condensation occurred on the entire head. 2000 in this state
When left in this environment for more than an hour, no occurrence of corrosion, deterioration of recording characteristics and reproduction signals was observed. Although the description has been given by taking the VTR magnetic head as an example, the effect of the present invention can be applied to a magnetic disk, a magnetic tape device using helical scan, and the like, and does not depend on the device.

FIG. 4 shows an example of a magnetic tape device.

[0017]

According to the present invention, a soft magnetic film having a high saturation magnetic flux density of Bs ≧ 1.5 T or more, exhibiting good soft magnetic properties, and having high thermal stability and high corrosion resistance can be obtained. be able to. As a result, a magnetic head having high performance and high reliability and a magnetic recording device using the same can be obtained. In particular, in various magnetic recording devices such as a VTR device, a magnetic tape device and a magnetic disk device, a magnetic recording medium having a high coercive force can be sufficiently magnetized, so that high density recording is possible.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the composition of a magnetic film of the present invention and corrosion resistance.

FIG. 2 is a diagram showing a structure of a magnetic film of the present invention.

FIG. 3 is a diagram showing a structure of a magnetic head of the present invention.

FIG. 4 is a block diagram showing an example of a magnetic tape device to which the magnetic recording device of the present invention has been applied.

[Explanation of symbols]

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

Claims (13)

[Claims] 1. A magnetic thin film comprising at least Hf and N and the balance being Fe, wherein the magnetic thin film has a polycrystalline structure comprising Fe crystal particles, Hf and N compound particles and / or Hf metal. The composition ratio of the compound particles of Hf and N is 1.2 or more, 1.7
A microcrystalline precipitation type magnetic thin film, which is as follows, and wherein the magnetic thin film has soft magnetic characteristics. 2. The method according to claim 1, wherein the compound particles of Hf and N are Hf ₄ N ₃ , Hf ₃ N ₂
The microcrystalline precipitation type magnetic thin film according to claim 1, wherein the magnetic thin film is at least one compound selected from the group consisting of: 3. Hf ₄ N ₃ , Hf ₃ N
_3. The microcrystalline precipitation-type magnetic thin film according to claim 2, wherein the deviation from the stoichiometric composition is ± 10%. 4. The microcrystalline precipitation type magnetic thin film according to claim 1, wherein the compound particles of Hf and N are nonstoichiometric compounds of Hf and N. 5. The fine particle according to claim 1, wherein the size of Fe crystal particles is 15 nm or less, and the size of Hf and N compound particles is 3 nm or less. Crystal precipitation type magnetic thin film. 6. The method according to claim 1, wherein the metal Hf in the Hf component is precipitated as a crystal phase and / or is precipitated at a grain boundary of Fe. The microcrystalline precipitation type magnetic thin film according to the above. 7. A method according to claim 1, wherein one part of N is dissolved in Fe and
7. The microcrystalline precipitation type magnetic thin film according to claim 1, wherein one part of N dissolved in the solid solution forms a compound with Fe. 8. For the Fe phase, by dissolving N in Fe and / or by depositing Hf at the crystal grain boundaries, and for the compound phase of Hf and N, the stoichiometry of Hf and N 8. The microcrystalline precipitation type magnetic thin film according to claim 1, wherein the crystal grain size is controlled by controlling the stoichiometric ratio. 9. The composition of the magnetic thin film, wherein the total of Hf and N is 15 at%.
From 25 at% to the ratio of Hf to N: (Hf) / (N)
The microcrystalline precipitation type magnetic thin film according to any one of claims 1 to 8, wherein the magnetic thin film is in a range of 0.5 to 1.5. 10. The soft magnetic film according to claim 1, wherein the soft magnetic film has a saturation magnetic flux density of 1.5 T or more, a coercive force of 1 Oe or less, and a magnetic permeability at 50 MHz of 1000 or more. The microcrystalline precipitation type magnetic thin film according to any one of the above. 11. A magnetic head using the soft magnetic film according to claim 1 as a soft magnetic film for a magnetic head. 12. A magnetic head using the soft magnetic film according to claim 1 as a metal-in-gap type magnetic head. 13. A magnetic recording apparatus using the magnetic head according to claim 11, wherein information is recorded on a moving information recording medium using magnetic properties.