JPH03263306A - Magnetic film and magnetic head - Google Patents

Abstract

PURPOSE:To obtain a magnetic film having large saturation magnetic flux density (Bs) of 16-18kG, excellent soft magnetic characteristics, and corrosion resistance and hardness superior to FeMC alloy film, by using a magnetic film of specified constituent FexMyNz. CONSTITUTION:The title magnetic film is constituted of FexMyNz composition. M is at least one kind of metal selected from a group constituted of Zr, Nb, Hf, Ta, Mo and Ti. N is nitrogen. When x, y, and z are represented by atomic percentage, the following hold; 70.5<=x<=84, 7<=y<=14, 9<=z<=15.5, and x+y+z=100. The FeMN film in this invention is formed by physical vapor growth method such as sputtering method and vacuum deposition method. Nitrogen can be supplied from the atmospheric gas or the matrix of the film. The FeMN film just after it has been formed contains amorphous phase, and Bs is lower than or equal to 15kG. By suitable heat treatment, the whole part of the film is turned into fine crystal grain texture, and the soft magnetic characteristics is improved, thereby obtaining Bs of 16-18kG. Heat treatment is performed in vacuum, or nitrogen gas or inert gas like argon.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magnetic film and a magnetic head, and particularly has excellent characteristics for high-density magnetic recording and reproduction required for digital VTRs, high-definition VTRs, etc. Regarding magnetic heads and magnetic core materials.

(Prior Art) Conventionally, ferrite, permalloy, sendust, Co-based amorphous, etc. have been used as magnetic herad core materials. However, these materials have a low saturation magnetic flux density (
Bs) is about 5kG for ferrite and 6 to 8 for permalloy.
kG, about 10kG with Sendust, G.

It is about 8 kG for an amorphous type, and in order to improve the characteristics of high-density magnetic recording and reproduction, it was necessary to increase Bs.

On the other hand, recently FeMC (M is Zr, Ti, Hf
, Ta, and Nb), a good soft magnetic film with a Bs of about 16 kG has been reported (IEICE Technical Report MR89-12 (1988)).
9)).

(Problem to be solved by the invention) However, this FeMC (M is Zr, Ti, Hf,
Soft magnetic films having a composition of Ta, Nb) have the following problems.

First, since it contains a large amount of carbon (C), it is susceptible to rust. In a corrosion test at 80°090%RH for 11,200 hours, a 30% decrease in Bs was observed, indicating the progress of rust (see Figure 5).

Second, the altitude is low. The Vickers hardness Hv of the FeMC film is about 400 at most, which is smaller than Hv600 of Sendust, which is currently in practical use in video heads and the like. Wear is a problem even with the current Sendust, so in the future VTRs, where the relative speed between the tape and the head will increase further to obtain digital images and high-definition images, and the tape tension will also increase, wear will become a problem. It is inevitable that the conditions will become stricter, making it difficult to put FeMC films into practical use.

Thirdly, the Bs in the composition range exhibiting good soft magnetic properties is at most 16 kG, and for example, compositions with Bs exceeding 17 kG will not provide good soft magnetic properties.

(IEICE Technical Report MR89-12 (1989)). In the field of magnetic recording, as recording density increases, core materials with increasingly larger s are required, and FeMC-based materials have had problems in this respect as well.

(Means for Solving the Problems) The present invention solves the above problems. Fex
A magnetic film characterized by having a composition of MyNz, where M is Zr, Nb, Hf, Ta, Mo, T.
at least one metal selected from the group consisting of i, where N is nitrogen, and where x, y, and z are atomic percents, respectively, 70.5<x<84 79d149<z<15.5 A magnetic film characterized in that x+y+z=100 and a magnetic head using the same.

As shown later, in the present invention, Zr, Nb, Hf
, Ta.

The content y of at least one metal selected from the group consisting of Mo and Ti is in the range of 7 to 14 at.%. Further, the nitrogen content 2 is in the range of 9 to 15.5 at%. When these y and z are satisfied and the remaining portion is Fe, excellent soft magnetic properties can be obtained. The FeMN film according to the present invention is formed by a physical vapor deposition method such as a sputtering method or a vacuum evaporation method. At this time, nitrogen can be supplied either from the atmospheric gas or from the base material of the membrane. The FeMN film immediately after deposition has a structure including an amorphous phase within the composition of the present invention, and Bs is 15 kG or less. By applying appropriate heat treatment to this film, the entire film becomes a microcrystalline structure, and the soft magnetic properties are improved and the Bs is also reduced to 16~16.
It becomes 18kG. Heat treatment is usually carried out in vacuum, nitrogen gas,
It is carried out in an inert gas such as argon gas.

The heat treatment temperature and time vary depending on the film thickness and composition, but
Generally, it is desirable that the temperature be 450'C to 550C, which is higher than the crystallization temperature, for about 5 minutes to 25 hours.

Conditions for heating and cooling during heat treatment can be arbitrarily changed depending on the conditions. Further, the heat treatment can be carried out multiple times at the same temperature or different temperatures, or the heat treatment can be carried out in a multi-stage heat treatment pattern. Furthermore, the present alloy can be heat treated directly or in an alternating magnetic field. Magnetic anisotropy can be produced in this alloy by heat treatment in a magnetic field. When a magnetic core made of this alloy film is heat-treated by applying a magnetic field in the direction of the magnetic path, a particularly high squareness ratio can be obtained, and when a magnetic field is applied perpendicular to the magnetic path and heat-treated, it has a low squareness and high magnetic permeability. It is a characteristic of

It is not necessary to apply a magnetic field throughout the heat treatment, and a sufficient effect can be obtained by applying it only at a temperature lower than the Curie temperature Tc of the alloy according to the present invention. The Tc of the alloy according to the present invention is higher in the microcrystalline phase formed by heat treatment than in the amorphous case immediately after sputtering, and heat treatment in a magnetic field is possible even at a higher temperature than the Tc of the amorphous phase. Applicable. Further, heat treatment in a rotating magnetic field may be performed as part of the heat treatment process. Further, the heat treatment can be performed in two or more stages. Furthermore, the magnetic properties can be adjusted by performing heat treatment while applying tension or compression.

(effect) The cause of soft magnetism in the FeMN film is considered to be as follows.

That is, FeMN film formed by physical vapor deposition method
The bccFe solid solidified grains of the film are formed by the heat treatment described above. At the same time, M atoms, which tend to form compounds with nitrogen, form nitrides when selected, thereby suppressing the growth of crystal grains.

As a result, it has a microcrystalline structure and exhibits good soft magnetism.

In addition, unavoidable impurities such as O, P, S, and H, Ca,
Sr.

Of course, even if Ba, Mg, etc. are contained to such an extent that the desired properties are not deteriorated, the alloy can be considered to be the same as the alloy of the present invention.

(Example) FeMN films of various compositions were formed with a film thickness of 2 to 6 □m on a crystallized glass substrate by sputtering. N was supplied by adding N2 gas during sputtering. After sputtering film formation, 50°C in vacuum below lXl0-5 Torr.
Heat treatment was performed at 0-550'C for 1 hour. Figure 1 shows
This is the coercive force He at various compositions when M is Ta in the FeMN composition film. In the region where Ta was 7 to 14 at% and N was 9 to 15.5 at%, He was 1 (Oe) or less, showing good soft magnetic properties.

FIG. 2 shows the saturation magnetic flux density Bs at various compositions when M is Ta in a FeMN composition film. In the region showing good soft magnetic properties in Figure 1, Bs is approximately 16 to 18.
It showed a large value of kG. In addition, when using this production method,
In order to obtain better magnetic properties, it is desirable that the film thickness is 2 pm or more.

FIG. 3 shows Ta: 8. Oat%, N: 13. Oat%,
FIG. 4 shows the magnetization curve of the FeTaN film made of residual Fe, and FIG. 4 shows the frequency characteristics of magnetic permeability of the same film as in FIG. The film had a low He value of 0.130e, a high Bs value of 18 kG, and a high magnetic permeability of 1650 even at IMHz of 6440.20 MHz, and had extremely good soft magnetic properties.

FIGS. 3 and 4 show typical characteristics of FeTaN films, and within the composition range shown in FIGS. 1 and 2, the FeTaN film has almost the same characteristics.

In FIG. 3, a large force of 18 kG is achieved with the FeTaN film. This is a conventional FeMC (M:Zr,
Ti, Hf.

This value was not reproduced with the Ta, Nb) films. Also, in FIG. 4, Fe79. lHf7.6C13,
3 (values are in atomic percent) The magnetic permeability of the film is shown by the broken line.

It can be seen that the magnetic film according to the present invention is also superior in magnetic permeability to the FeMC film.

The excellent soft magnetic properties as described above are due to the fact that Ta in the film is active and selectively nitrides with N in the film.

That is, when the film according to the present invention is subjected to an appropriate heat treatment after being sputtered, a bccFe solid solution crystal phase precipitates, and Ta selectively combines with N to generate nitrides such as TaN. This nitride significantly controls the growth of crystal grains, and the film after heat treatment becomes a film consisting of ultrafine crystal grains and exhibits good soft magnetism. FIG. 5 shows the change in Bs over time due to corrosion (rust) of the FeTaN film according to the present invention and the conventional FeZrC film in an atmosphere of 80° C. and 90% RH. FeZ
Since the rC film contains C, corrosion progresses, and Bs decreased to about 70% after 1200 hours. On the other hand, F
In the eTaN film, no decrease in Bs was observed even after 1200 hours. Furthermore, when the Vickers hardness Hv of the FeTaN film according to the present invention was measured, Hv=600-80
It was found that the hardness was larger than that of conventional FeMC, which had Hv<400, and had a hardness comparable to or even higher than that of Sendust.

As M, Zr other than Ta, Nb, Mo, Hf,
Similar results were obtained when using Ti. As mentioned above, this applies to Zr, Nb, Hf as well as Ta.
, Ti is active and N is selectively released in the film by heat treatment.
Its magnetic properties are explained by the fact that the film has a microcrystalline structure similar to that of Ta. Further, as in the case of Ta, improved corrosion resistance and height were obtained.

Next, Fe (7
A film with a composition of
A magnetic head having the structure shown in FIG. 6 was manufactured by forming a four-layer film with a thickness of μm and having a film thickness equal to the track width. FeTaN
The magnetic properties of the film were a saturation magnetic flux density of 4πMs 17 kG and a magnetic permeability of about 2000 (at 20 MHz). FIG. 7 shows the frequency dependence of the normalized output of this head when a metal tape (coercive force 15000e) is used and the tape head relative speed is 21 m/see. In addition, Fe5iAl
The characteristics of the conventional head using the alloy film are shown below. Fe5iA
The magnetic properties of one film are 4πMs 10kG, μ is approximately 1001
000 (at 20).

Due to the high 4πMs and high □ characteristics of the FeTaN film, a greater output than conventional heads can be obtained even at high frequencies.

When not only the FeTaN film but also a soft magnetic metal film having the other compositions mentioned above was used, a film with a large 4πMs and a high μ could produce a head with a high output.

(Effect of the invention) As described above, the present invention provides a large load s of 16 to 18 kG.
FeMC has good soft magnetic properties, and is also composed of conventionally known FeMC (M is Zr, Hf, Ti, Ta, N
b) A magnetic film for a magnetic core of a magnetic head having corrosion resistance and hardness superior to alloy films can be obtained. In addition, a magnetic head that can obtain large output even at high frequencies has been realized.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the He value depending on the composition of the FeTaN composite film, Fig. 2 is a diagram showing the Bs value depending on the composition of the FeTaN composite film, and Fig. 3 is a diagram showing the value of Bs depending on the composition of the FeTaN composite film. Figure 4 is a typical permeability frequency characteristic diagram of FeTaN film, Figure 5 is a typical magnetization curve diagram of FeTaN film, and Figure 5 is a typical magnetization curve diagram of FeTaN film.
FIG. 3 is a diagram showing changes in Bs over time when a TaN film and a FeZrC film are left as they are. , FIG. 6 is an external view of the magnetic head according to the present invention, in which 1 is a ceramic or glass substrate;
2 is a metal soft magnetic film, and FIG. 7 is a diagram showing the frequency characteristics of the output of the magnetic head according to the present invention.

Claims (1)

[Claims] (1) A magnetic film characterized by having a composition of Fe_xM_yN_z, where M is Zr, Nb, Hf, Ta,
At least one metal selected from the group consisting of Mo and Ti, where N is nitrogen, and where x, y, and z are atomic percent, respectively 70.5<x<84 7≦y≦14 9<z <15.5 x+y+z=100. (2) A magnetic head characterized in that the magnetic film according to claim 1 is used as a magnetic core.