JPH07307003A - Magnetic head and magnetic recording and reproducing device using the same - Google Patents

Abstract

PURPOSE:To obtain a magnetic head which suppresses corrosion of magnetic films generated in a magnetic head state and has high reliability. CONSTITUTION:This magnetic head is composed of the magnetic thin films 1 having soft magnetic characteristics and substrates 2 having an electrical conductivity. The difference between the potential at which the electrochemical reaction exhibited by the magnetic films 1 of the magnetic head described above is generated and the potential at which the electrochemical reaction exhibited by the substrates 2 is generated is confined to <=1.0V. As a result, the galvanic corrosion of the galvanic cell formed between the substrates having the electrical conductivity and the magnetic films is suppressed and, therefore, the corrosion generated in the magnetic head state is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head including a conductive substrate and a magnetic thin film having soft magnetic characteristics, and more particularly to a magnetic head having high reliability and a magnetic recording / reproducing apparatus using the same.

[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 information storage device. Among them, studies on high-density recording and downsizing of magnetic recording devices are being rapidly advanced. In order to realize high-density magnetic recording, a magnetic recording medium having a high coercive force for allowing minute recording magnetic domains to exist stably,
A high-performance magnetic head with a large magnetomotive force is required to stably record information on the medium. In order to obtain a magnetic head capable of recording a signal by sufficiently magnetizing a high coercive force medium, a magnetic head material having a high saturation magnetic flux density and capable of generating a strong magnetic field is required.

As a magnetic material having a high saturation magnetic flux density, Fe-C system represented by Fe-Ta-C, Fe-T.
A compound system of an iron group element such as a-N and Fe-Zr-N represented by Fe-N system and C or N is known. These magnetic materials were subjected to heat treatment at a constant temperature in an inert gas stream such as argon or nitrogen while applying a magnetic field of about 3 to 10 kOe as needed to develop soft magnetic properties. . When the magnetic head is a metal-in-gap (MIG) type head, a glass bonding step is included in the head manufacturing step, and the heat treatment temperature is determined by this bonding temperature.

Further, since the magnetic material is mainly composed of Fe, it reacts with oxygen and water in the atmosphere to generate hydroxides and oxides, and has magnetic properties, particularly coercive force and saturation magnetic flux density. Due to the fluctuation, the performance of the magnetic head may be deteriorated. In practical application of a magnetic head using the above magnetic material, changes in magnetic characteristics over time (deterioration) due to corrosion
It is necessary to suppress the
It is described in JP-A-3-20444 that an element for the purpose of improving corrosion resistance is added in addition to the magnetic element.

[0005]

Conventionally, the corrosion resistance of the magnetic film itself has been studied. However, when a magnetic head using this magnetic film is manufactured, the corrosion resistance of the magnetic film causes the magnetic film to be on a non-conductive substrate. It was deteriorated more than when it was formed on the surface, and this point has not been sufficiently studied. Therefore, even if a soft magnetic film having high reliability is used, sufficient reliability as a magnetic head is not always obtained, and there is a problem that reproduction output is lowered or sufficient recording characteristics cannot be obtained during use. It happened.

It is an object of the present invention to provide a highly reliable magnetic head in which sufficient corrosion resistance is ensured for a magnetic thin film having soft magnetic characteristics and a magnetic recording device using the same. It is another object of the present invention to provide a magnetic recording apparatus using the magnetic head in which the deterioration of the recording / reproducing characteristics due to the deterioration of the magnetic film for the magnetic head is very slight even when used for a long time.

[0007]

A magnetic head is made of not only a magnetic film but also a composite material such as a conductive substrate, bonding glass, and a metal layer. Therefore, the reliability as a magnetic head may not always be sufficiently ensured only by improving the corrosion resistance of the magnetic film itself in order to form an electrochemical corrosion battery between the materials forming the magnetic head.
The inventors have completed the present invention by paying attention to this point.

A magnetic head according to the present invention includes a conductive substrate and a magnetic film provided on the substrate and having a soft magnetic characteristic. The magnetic film has a potential for causing an electrochemical reaction and the substrate. It is characterized in that the difference from the potential causing the electrochemical reaction shown is 1.0 V or less. It is preferable that the potential of the magnetic film that causes an electrochemical reaction is nobler than the potential of the substrate that causes an electrochemical reaction. Here, the potential that causes the electrochemical reaction is a measured value in a normal use environment, that is, pH 5 to pH 9
It is a value in an aqueous solution in the range of.

The conductive substrate is preferably made of a magnetic material, and single crystal Mn.Zn ferrite is preferable because it has good magnetic characteristics. The magnetic film is Zr, Nb, T
5-20 at least one element selected from a
1% to 20 at% of at least one element selected from at% and N, C, Cr, Nb, Al, Pt, Ru,
At least one or two kinds of additive elements selected from Rh and Ti are contained in an amount of 0.5 to 15 at%, and the balance is F.
The alloy is preferably at least one element selected from e, Co, and Ni, and the crystallization temperature can be controlled by controlling the concentration of the additional element. Here, when selecting Nb from the group of Zr, Nb, and Ta, an element other than Nb is selected as an additive element. Z
When Zr or Ta is selected from r, Nb and Ta, Nb may be selected as an additive element.

Specifically, the alloy is Fe--Ta--C.
-Cr-Ru, Fe-Ta-C-Cr-Rh, Fe-T
a-C-Al, Fe-Ta-C-Cr-Ti, Fe-T
a-C-Cr-Nb, Fe-Ta-N-Al, Fe-T
a-N-Cr-Ru, Fe-Ta-N-Cr-Rh, F
e-Ta-N-Cr-Rh, Fe-Ta-C-Al-R
u, Fe-Ta-N-Al-Ru, Fe-Nb-C-C
r-Ru, Fe-Nb-C-Cr-Rh, Fe-Nb-
C-Al, Fe-Nb-C-Cr-Ti, Fe-Nb-
N-Al, Fe-Nb-N-Cr-Ru, Fe-Nb-
N-Cr-Rh, Fe-Nb-N-Cr-Rh, Fe-
Zr-C-Cr-Ru, Fe-Zr-C-Cr-Rh,
Fe-Zr-C-Al, Fe-Zr-C-Cr-Ti,
Fe-Zr-C-Cr-Nb, Fe-Zr-N-Al,
Fe-Zr-N-Cr-Ru, Fe-Zr-N-Cr-
Rh, Fe-Zr-N-Cr-Rh, Fe-Zr-C-
Al-Rn, Fe-Zr-N-Al-Ru, Co-Ta
-C-Cr-Ru, Co-Ta-C-Cr-Rh, Co
-Ta-C-Al, Co-Ta-C-Cr-Ti, Co
-Ta-C-Cr-Nb, Co-Ta-N-Al, Co
-Ta-N-Cr-Ru, Co-Ta-N-Cr-R
h, Co-Ta-N-Cr-Rh, Co-Ta-CA
l-Ru, Co-Ta-N-Ru-Al, Co-Nb-
C-Cr-Ru, Co-Nb-C-Cr-Rh, Co-
Nb-C-Al, Co-Nb-C-Cr-Ti, Co-
Nb-N-Al, Co-Nb-N-Cr-Ru, Co-
Nb-N-Cr-Rh, Co-Nb-N-Cr-Rh,
Co-Nb-C-Al-Ru, Co-Nb-N-Al-
Ru, Co-Zr-C-Cr-Ru, Co-Zr-C-
Cr-Rh, Co-Zr-C-Al, Co-Zr-C-
Cr-Ti, Co-Zr-C-Cr-Nb, Co-Zr
-N-Al, Co-Zr-N-Cr-Ru, Co-Zr
-N-Cr-Rh, Co-Zr-N-Cr-Rh, Co
-Zr-C-Al-Ru, Co-Zr-N-Ru-A
1, Ni-Ta-C-Cr-Ru, Ni-Ta-C-C
r-Rh, Ni-Ta-C-Al, Ni-Ta-C-C
r-Ti, Ni-Ta-C-Cr-Nb, Ni-Ta-
N-Al, Ni-Ta-N-Cr-Ru, Ni-Ta-
N-Cr-Rh, Ni-Ta-N-Cr-Rh, Ni-
Ta-C-Al-Ru, Ni-Ta-N-Al-Ru,
Ni-Nb-C-Cr-Ru, Ni-Nb-C-Cr-
Rh, Ni-Nb-C-Al, Ni-Nb-C-Cr-
Ti, Ni-Nb-N-Al, Ni-Nb-N-Cr-
Ru, Ni-Nb-N-Cr-Rh, Ni-Nb-N-
Cr-Rh, Ni-Nb-C-Al-Ru, Ni-Nb
-N-Al-Ru, Ni-Zr-C-Cr-Ru, Ni
-Zr-C-Cr-Rh, Ni-Zr-C-Al, Ni
-Zr-C-Cr-Ti, Ni-Zr-C-Cr-N
b, Ni-Zr-N-Al, Ni-Zr-N-Cr-R
u, Ni-Zr-N-Cr-Rh, Ni-Zr-NC
r-Rh, Ni-Zr-C-Al-Ru, Ni-Zr-
It can be N-Al-Ru or the like.

Here, the concentration of at least one element selected from Zr, Nb, and Ta is set to 5 to 20 at% when the concentration is less than 5 at% to obtain a magnetic film having good soft magnetic characteristics. If it exceeds 20 at%, the coercive force will increase, the soft magnetic properties will deteriorate, and the magnetism itself will be lost. The coercive force of less than 1.0 Oe is more preferable in the range of 5 to 15 at%.

The concentration of at least one element selected from N and C is set to 1 to 20 at% because if the content is less than 1 at% or more than 20 at%, good soft magnetic properties cannot be obtained even by heat treatment. Because. It should be noted that the range of 8 to 15 at% is more preferable because better soft magnetic characteristics can be obtained. Cr, Nb, Al, Pt, Ru, Rh, T
The concentration of at least one or two elements selected from i is 0.5 to 15 at% is 0.5a.
This is because if it is less than t%, the corrosion resistance and heat resistance of the magnetic film cannot be secured, and if it exceeds 15 at%, the soft magnetic properties are deteriorated such as an increase in coercive force. It should be noted that the content of 3 to 10 at% is more preferable because deterioration of soft magnetic properties is small and corrosion resistance and heat resistance can be secured. These additional elements act to suppress the growth of crystal grains by precipitating as a compound at the crystal grain boundary or by forming an alloy such as an intermetallic compound with a metal such as Fe, Co or Ni, and as a result, Corrosion resistance can be improved without deteriorating magnetic properties. Among these materials, the Fe-based material is most preferable because the maximum saturation magnetic flux density can be obtained.

Since the soft magnetic characteristics of the soft magnetic film depend on the size of fine crystal grains to be deposited, the crystal grain size must be controlled in order to obtain a magnetic film having good soft magnetic characteristics. The soft magnetic film according to the present invention can be formed into a soft magnetic thin film exhibiting soft magnetic properties by heat treatment, and the crystallization temperature of the thin film immediately after film formation is controlled, and the particle size is 1 to 15 nm. It is preferable to include some α-Fe phase crystallites.

Controlling the composition of the substrate is effective for controlling the potential that causes an electrochemical reaction in the conductive substrate. This is because the elements contained in the substrate material change. For example, in a Mn.Zn ferrite substrate, if the concentration of divalent Fe ions is changed significantly,
The apparent potential at which oxidation occurs can be changed. Alternatively, the crystal orientation in the polycrystalline substrate and the single crystal substrate, or in the single crystal may be controlled.

In order to control the potential that causes an electrochemical reaction in the magnetic film having soft magnetic characteristics, the composition of the magnetic film may be controlled, or an element may be added to control the potential. You may control the addition concentration. The magnetic head according to the present invention may be a metal-in-gap (MIG) type magnetic head. However, it goes without saying that the magnetic head having a conductive substrate and a magnetic film is not limited to the form.

When the magnetic head according to the present invention is used in a magnetic recording / reproducing apparatus and information such as image information and audio information is magnetically recorded / reproduced on a moving information recording medium, the reproduced signal can be increased and good recording can be achieved. Playback can be performed. As the information recording medium, a magnetic tape or a magnetic disk having a magnetic recording medium layer formed on a disc can be used.

[0017]

The electrochemical reaction occurring between the magnetic film forming the magnetic head and the conductive substrate is an oxidation reaction of the magnetic film. When the potential of the conductive reaction of the conductive substrate is higher than the potential of the magnetic reaction of the magnetic film,
The conductive film is corroded, and the magnetic film is corroded when the potential of causing an electrochemical reaction of the magnetic film is higher than the potential of causing the electrochemical reaction of the conductive substrate.

Therefore, the corrosion of the magnetic film can be suppressed by controlling the potential at which this oxidation reaction occurs. That is, when the difference between the oxidation potential of the soft magnetic thin film and the oxidation potential of the conductive substrate is 1.0 V or less, the oxidation reaction rate of the soft magnetic thin film is small and can be almost ignored. In addition,
The potential at which an electrochemical reaction occurs changes depending on pH (63
mV / pH), it is necessary to measure the oxidation potential in a normal use environment, that is, pH5 to pH9.

As described above, according to the present invention, since the oxidation reaction of the magnetic film (corresponding to the corrosion reaction of the magnetic film) can be controlled, the corrosion of the magnetic film can be suppressed. This corresponds to controlling the action of the electrochemical cell formed between the magnetic film and the conductive substrate by controlling the electrochemical potential difference. Further, in the present invention, the corrosion resistance of the magnetic head is improved by controlling the electrochemical characteristics of the soft magnetic thin film and the substrate, and since the magnetic characteristics of the magnetic film are not deteriorated, high performance such as high saturation magnetic flux density is achieved. A magnetic head can be provided.

[0020]

EXAMPLES The details of the present invention will be described below with reference to examples. [Example 1] As a magnetic thin film, Fe-Ta-C-Cr-
An Nb alloy film was used. A sputtering method was used for forming the magnetic film. The targets for sputtering are Fe, Ta, C, N.
The powder of each element of b and Cr is subjected to hot isostatic pressing (HIP
Method) was used. The composition of the target was (Fe ₇₃ Ta ₇ C ₈ ) ₉₅ (Cr ₅₀ Nb ₅₀ ) ₅ . When this target was used, the composition of the obtained film remained almost unchanged even when the film was thinned, and was almost the same as the target composition. It goes without saying that C may be TaC, NbC or CrC and the powder may be molded by the hot isostatic pressing method (HIP method).

On the crystallized glass substrate, the alloy target was used and sputtering was performed using Ar as a discharge gas. The thickness of the magnetic film thus formed is 5 μm. The sputtering conditions were a discharge gas pressure of 5 mTorr and an input RF power of 400 W. Regarding the magnetic characteristics of the obtained magnetic film, the saturation magnetic flux density was 1.6 T, the coercive force was 0.1 Oe, the relative magnetic permeability at 5 MHz was 4500, and the magnetostriction constant was 5 × 10 ⁻⁷ .

The polarization curves of the magnetic film and the ferrite substrate thus produced were measured by the potential scanning method (100 m
V / min). The pH of the electrolytic solution was adjusted to 8.3 with a borate buffer solution. The result is shown in FIG. Mn / Zn
As a ferrite substrate, the ratio of MnO and ZnO is 2.
Three types different from 2, 1.9 and 1.5 were used. Here, the Mn / Zn ferrite substrate is 0.3T to 0.5
It is a magnetic substance having a saturation magnetic flux density of about T.

From the extrapolated value of each polarization curve shown by the broken line in FIG. 1, the oxidation potential of the magnetic film is -0.1 V (vs. Ag / Ag).
Cl electrode reference, the same applies hereinafter), and the oxidation potential of the Mn.Zn ferrite substrate is 0.2 V (MnO / ZnO = 1.
5), 0.7 V (MnO / ZnO = 1.9) and 1.2
It can be seen that V (MnO / ZnO = 2.2). Next, using the magnetic film, three types of Mn.Zn ferrite substrates having different ratios of MnO and ZnO of 2.2, 1.9, and 1.5 are used, and shown schematically in FIG. An MIG (metal in gap) type magnetic head was manufactured.

In manufacturing the magnetic head, the soft magnetic thin film 1 was formed on a single crystal ferrite substrate 2. As the gap portion 3, SiO ₂ was formed to a thickness of 140 nm and then Cr was formed 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 gas stream at 600 ° C. for 1 hour to develop soft magnetic characteristics, and head substrates of the same shape were bonded with a low melting point glass 4. A bonding layer may be provided between the substrate and the magnetic film to improve the adhesiveness between them. The temperature of the heat treatment for exhibiting the soft magnetic characteristics is determined by the crystallization temperature of the magnetic film, and is not limited to this value.

This magnetic head was immersed in a 0.5N sodium chloride aqueous solution for 100 hours, and the reliability of the magnetic head was evaluated by visual observation. As a result, MnO and ZnO
Corrosion was not observed at all in the magnetic head using the ferrite substrate having the ratio of 1.5 and 1.9. On the other hand, in the magnetic head using the ferrite substrate having a ratio of MnO and ZnO of 2.2, the entire surface of the magnetic film was corroded by immersion for 5 hours. The above two types of magnetic heads that did not corrode were left to stand in a 95% RH environment at 80 ° C. for 2000 hours or more, but neither corrosion nor change in magnetic properties was observed.

From these results, it is understood that when the difference between the oxidation potential of the magnetic film and the oxidation potential of the conductive substrate is within 1 V, the magnetic film is not corroded. Good soft magnetic properties can be obtained by controlling the crystal grain sizes of Fe and TaC to 5 to 20 nm and 3 to 8 nm, respectively. In particular, with respect to the particle size of Fe, the saturation magnetic flux density Bs increases as the size increases in a region where the particle size is constant, but the coercive force also increases, so that the size is naturally limited. Further, the particle size of TaC is preferably made fine in view of the relationship between the Fe phase and the corrosion battery, and the size region where good corrosion resistance is obtained is 3 to 8 nm. As described above, the particle size of each phase affects the magnetic properties, and thus needs to be controlled.

Using these three types of MIG (metal in gap) type magnetic heads, a VTR device was manufactured, and a magnetic tape was run to record image information. When recording and reproducing high-definition digital information, the S / N was 40 dB. Here, the relative speed between the magnetic head and the magnetic tape is 36 m / s, and the data rate is 46.1 Mbp.
s, the track width is 40 μm.

This magnetic head was subjected to an immersion test method in a 0.5N aqueous sodium chloride solution and a dew condensation test method in a high temperature and high humidity environment (60 ° C., relative humidity 95%).
It was evaluated in terms of recording / reproducing characteristics. First, the MIG type head chip was immersed in a 0.5N sodium chloride aqueous solution for 200 hours. Then, the head was set again in the apparatus and the recording / reproducing characteristics were measured. As a result, MnO and Zn
In the device using the magnetic head using the substrates with O ratios of 1.5 and 1.9, the S / N was 40 dB, and no difference was observed in the recording / reproducing characteristics from before the immersion. The evaluation by the dew condensation test method in a high temperature and high humidity environment (80 ° C., 95% relative humidity) was carried out by fixing the MIG head on a Peltier element and keeping it at 10 ° C.
It was left in the environment. As a result, dew condensation occurred on the entire head, and the head was left in this environment for 2000 hours or more, but no corrosion or deterioration of recording or reproduction signals was observed.

On the other hand, the ratio of MnO and ZnO is 2.
In the magnetic head using the substrate of No. 2, the high temperature and high humidity environment (8
Both recording and reproduction could not be performed both in a dew condensation test at 0 ° C. and a relative humidity of 95%) and when immersed in a 0.5N sodium chloride aqueous solution for 200 hours. This is because the magnetic characteristics deteriorated due to corrosion of the magnetic film. Although the magnetic head for a VTR has been described above as an example, the present invention is also applicable to a magnetic head such as a magnetic tape device using a magnetic disk or a helical scan, and is not affected by the type of device to be applied. .

[Example 2] As a magnetic thin film, Fe-Ta was used.
A -C-Al alloy film was used. A sputtering method was used for forming the magnetic film. The sputtering target is Fe, Ta,
The powder of each element of C and Al is subjected to hot isostatic pressing (HIP
Method) was used. The composition of the target was (Fe ₈₀ Ta ₈ C ₁₂ ) ₉₁ Al ₉ . When this target was used, the composition of the obtained film remained almost unchanged even when the film was thinned, and was almost the same as the target composition.

On the crystallized glass substrate, the above alloy target was used and sputtering was performed using Ar as a discharge gas. The thickness of the magnetic film thus formed is 5 μm. The sputtering conditions were a discharge gas pressure of 5 mTorr and an input RF power of 400 W. Regarding the magnetic characteristics of the obtained magnetic film, the saturation magnetic flux density was 1.4 T, the coercive force was 0.2 Oe, the relative magnetic permeability at 5 MHz was 3500, and the magnetostriction constant was 2 × 10 ⁻⁶ .

The magnetic film and MnO produced in this way
The polarization curve of the Mn.Zn ferrite substrate with a ratio of ZnO and ZnO of 1.0 was measured by the potential scanning method (100 mV / min).
did. The pH of the electrolytic solution was adjusted to 8.3 with a borate buffer solution. The result is shown in FIG. From the extrapolated value of each polarization curve indicated by the broken line in FIG. 3, the oxidation potential of the magnetic film is 0.1 V (v
s. Ag / AgCl electrode reference, same below), and Mn
-It can be seen that the oxidation potential of the Zn ferrite substrate is -0.05V.

Next, using this magnetic film and the Mn.Zn ferrite substrate, a MIG (metal in gap) type magnetic head schematically shown in FIG. This magnetic head was immersed in a 0.5N sodium chloride aqueous solution for 100 hours, and the reliability of the magnetic head was evaluated by visual observation. As a result, no occurrence of corrosion was observed. Even when this magnetic head was left to stand in an environment of 95% RH at 80 ° C. for 2000 hours or more, neither corrosion nor change in magnetic characteristics was observed.

As described above, even when the oxidation potential of the conductive substrate is lower than the oxidation potential of the magnetic film, the magnetic film is not corroded. However, it should be noted that the substrate will corrode if the difference in oxidation potential is 1 V or more. Using the MIG (metal-in-gap) type magnetic head of this embodiment, a VTR device was manufactured, and a magnetic tape was run to record image information. When recording and reproducing high-definition digital information, the S / N was 39 dB. Here, the relative speed between the magnetic head and the magnetic tape is 3
The data rate is 6 m / s, the data rate is 46.1 Mbps, and the track width is 40 μm.

This magnetic head was subjected to the immersion test method in a 0.5N sodium chloride aqueous solution and the dew condensation test method in a high temperature and high humidity environment (60 ° C., relative humidity: 95%), and the above-mentioned example was used. Similarly, when evaluated in terms of recording / reproducing characteristics, the S / N was 39 dB, and no difference was observed in the recording / reproducing characteristics before immersion.

[Example 3] As the magnetic thin film, an Fe-Ta-N-Al alloy film formed on a ferrite substrate by sputtering to a thickness of 5 µm was used. The sputtering conditions were Ar / N ₂ (= 90/10) as the discharge gas,
The discharge gas pressure was 5 mTorr, the input RF power was 400 W, and a composite target in which Ta and Al pellets were placed on a Fe plate was used as a target. The magnetic film was heat-treated in an argon atmosphere at a temperature higher than the crystallization temperature by 60 ° C. for 30 minutes to exhibit soft magnetic characteristics.

The magnetic characteristics of the obtained magnetic film were a saturation magnetic flux density of 1.4 T, a coercive force of 0.2 Oe, a relative magnetic permeability of 4500 at 5 MHz and a magnetostriction constant of 8 × 10 ^-7 .
When the polarization curve of the magnetic film thus produced was measured by the potential scanning method (100 mV / min), it was -0.
It was 1V. The pH of the electrolytic solution is 8.
Adjusted to 3.

Next, the magnetic film and MnO / ZnO
5 (oxidation potential is 0.2 V), 1.9 (oxidation potential is 0.7
V) and 2.2 (oxidation potential is 1.2 V) of three types of Mn
Using a Zn ferrite substrate, a MIG (metal in gap) type magnetic head schematically shown in FIG. 2 was produced in the same manner as in Example 1. This magnetic head was immersed in a 0.5N sodium chloride aqueous solution for 100 hours, and the reliability of the magnetic head was evaluated by visual observation. As a result, M
No corrosion was observed at all in the magnetic head using the ferrite substrate having a ratio of nO to ZnO of 1.5 and 1.9. On the other hand, in the magnetic head using the ferrite substrate having a ratio of MnO and ZnO of 2.2, the entire surface of the magnetic film was corroded by immersion for 5 hours.

Using these three types of MIG (metal-in-gap) type magnetic heads, a VTR device was manufactured, and a magnetic tape was run to record image information. When recording and reproducing high-definition digital information, the S / N was 40 dB. Here, the relative speed between the magnetic head and the magnetic tape is 36 m / s, and the data rate is 46.1 Mbp.
s, the track width is 40 μm. This magnetic head was immersed in a 0.5N sodium chloride aqueous solution in the same manner as in Example 1, and a high temperature and high humidity environment (60
The dew condensation test method was performed in a temperature of 90 ° C. and a relative humidity of 95%, and the recording and reproducing characteristics were evaluated.

As a result, in the device using the magnetic head using the substrates whose MnO and ZnO ratios are 1.5 and 1.9,
The S / N was 40 dB, and there was no difference in recording / reproducing characteristics from those before the immersion test and the condensation test. On the other hand, in the magnetic head using the substrate having the ratio of MnO and ZnO of 2.2, neither recording nor reproducing was possible in both the immersion test and the condensation test. This is because the magnetic characteristics deteriorated due to corrosion of the magnetic film. As is clear from the above results, the effect of the present invention is not dependent on the material system, but is based on the electrochemical oxidation potential difference between the magnetic film and the substrate on which it is formed.

[0041]

According to the present invention, the corrosion battery action formed between the conductive substrate and the magnetic film can be suppressed, so that the corrosion generated in the magnetic head state can be suppressed. In composition control of the magnetic film performed for controlling the redox potential, good soft magnetic properties can be obtained while having a high saturation magnetic flux density without deteriorating the magnetic properties of the magnetic film, and further, the corrosion resistance of the magnetic film is improved, Furthermore, the characteristics of the magnetic head can be improved. When this magnetic head is used, a magnetic recording device having high performance and high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing polarization curves of a magnetic film and a substrate having conductivity.

FIG. 2 is a diagram showing a structure of a metal in gap (MIG) type magnetic head.

FIG. 3 is a diagram showing polarization curves of a magnetic film and a substrate having conductivity.

[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 Shigekazu Otomo 1-280 Higashikoigakubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory

Claims (12)

[Claims] 1. A conductive substrate and a magnetic film having a soft magnetic property, which is provided on the substrate, and a potential for causing an electrochemical reaction shown by the magnetic film and an electrochemical reaction shown by the substrate. A magnetic head characterized in that a difference from a potential causing a reaction is 1.0 V or less. 2. The magnetic head according to claim 1, wherein the potential for causing an electrochemical reaction indicated by the magnetic film is a nobler potential than the potential for causing an electrochemical reaction indicated by the substrate. 3. The magnetic head according to claim 1, wherein the electrochemical reaction is an oxidation reaction. 4. The magnetic head according to claim 1, 2 or 3, wherein the conductive substrate is made of a magnetic material. 5. The magnetic head according to claim 4, wherein the magnetic material is single crystal Mn.Zn ferrite. 6. The magnetic film contains 5 to 20 at% of at least one element selected from Zr, Nb and Ta.
1 to at least one element selected from N and C
20 at%, Cr, Nb, Al, Pt, Ru, Rh, T
0.5 to 15 at% of at least one or two elements selected from i, the balance being Fe, Co, N
6. The magnetic head according to claim 1, wherein the magnetic head is an alloy that is at least one element selected from i. 7. The magnetic film is a soft magnetic thin film that exhibits soft magnetic properties by heat treatment, and contains α-Fe phase fine crystals having a particle size of 1 to 15 nm. The magnetic head according to claim 6. 8. The magnetic head according to claim 7, wherein the magnetic film is a soft magnetic thin film which is subjected to heat treatment after film formation to exhibit soft magnetic characteristics. 9. The magnetic head according to claim 1, wherein the magnetic head is a metal-in-gap type magnetic head. 10. A magnetic recording / reproducing apparatus comprising: the magnetic head according to claim 1; a magnetic recording medium driving means; and a signal processing means. 11. The magnetic recording / reproducing apparatus according to claim 10, wherein the magnetic recording medium driving means drives a tape-shaped magnetic recording medium or a disk-shaped magnetic recording medium. 12. The magnetic recording / reproducing apparatus according to claim 10, wherein image information and / or audio information is recorded / reproduced.