JPH0738344B2 - Soft magnetic thin film - Google Patents

Description

The present invention relates to a soft magnetic thin film used for a magnetic head, a magnetoresistive element, and the like, and particularly to excellent recording / reproducing characteristics for a medium for high-density magnetic recording with high coercive force. And a magnetic head using the same.

2. Description of the Related Art Conventionally, ferrite, which is a metal oxide, has been widely used as a material for magnetic heads. In recent years, permalloy (nickel-iron-based alloy) and sendust (iron-aluminum-silicon-based alloy) having higher saturation magnetic flux density than that have been used.

More recently, Amosface materials with a saturation magnetic flux density of 1.0 to 1.4 Tesla (cobalt-zirconium amorphous alloy)
Has been developed and is beginning to be used for metal tape compatible heads such as 8 mm VTR.

In response to the demand for higher recording density, magnetic materials with high saturation magnetic flux densities have been introduced one after another, but the progress of media has been remarkable, and the advent of metal tape has made it possible to maintain the conventional oxide tape with a holding power of 600 ~. 1500-2000 for 700e
A medium having a coercive force of e has been obtained.

In the next-generation large-capacity magnetic recording media, media with even greater coercive force are under development, and a magnetic head core having a saturation magnetic flux density of 1.5 Tesla or more is required to sufficiently record on such high coercive force magnetic recording media. It is said that a magnetic material for use is required [for example, "Hitachi" Vol. 49, No. 6, 8-9].
page〕.

A material with a high saturation magnetic flux density is pure iron of 2.2 Tesla. However, since pure iron has a low magnetic permeability, it cannot be used as a magnetic head material as it is. Therefore, iron carbide-based multilayer films have been studied, and soft magnetic thin films having high saturation magnetic flux density and magnetic permeability have been reported [for example, Journal of Applied Physics].
hysics) ”, Vol. 63, No. 8, April, 1988, pp. 3203-3205,“ Japan Society for Applied Magnetics, ”Vol. 12, No. 3, 1988, pp. 460-464]. However, there is a problem in terms of corrosion resistance, etc., and it has not been put to practical use. On the other hand, research on iron nitride thin films with high corrosion flux and high saturation magnetic flux density has been reported [for example, "The 11th Annual Meeting of the Applied Magnetics Society of Japan" 3pB-13, 19
87]. However, the thin film does not have high magnetic permeability.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, a magnetic material having a saturation magnetic flux density of 1.5 tesla or more has a problem that a material having both high durability and magnetic permeability cannot be obtained so far.

In view of the above problems, the present invention provides a soft magnetic thin film having both high durability and magnetic permeability and high saturation magnetic flux density, and a magnetic head using the same.

Means for Solving the Problems In order to solve the above problems, the soft magnetic thin film of the present invention comprises a layer of iron carbide having a C concentration of 3 to 20% by mole percentage, and an iron nitride containing γFe ₄ N as a main component. The layers are interleaved and the thickness of the iron carbide monolayer is 0.5-1500 nm, the thickness of the iron nitride monolayer is 0.5.
It has a structure of ~ 1000 nm.

Action The present invention has a high magnetic permeability of the iron carbide layer and a high durability of the iron nitride layer by the above-described configuration, which complement each other, and has a high magnetic permeability and a high saturation magnetic flux density of 1.5 Tesla or more. A soft magnetic thin film is provided.

Example A soft magnetic thin film according to a first example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a layered structure of iron carbide and iron nitride in the soft magnetic thin films of the first and second embodiments of the present invention. In FIG. 1, 11 is iron carbide and 12 is iron nitride.

The soft magnetic thin film of this embodiment was produced by using a 3-target type high frequency magnetron sputtering apparatus, the film thickness of each layer was controlled by the sputtering time, and the total film thickness was about 2 μm regardless of the film thickness of each layer. The number of layers is adjusted so that Further, all the soft magnetic thin films of this example were annealed at 320 ° C. for 1 hour after the film formation.

The characteristics of the soft magnetic thin film having the above structure will be described with reference to Tables 1 and 2 and FIGS.

First, Table 1 shows that the iron nitride layer has a thickness of 5 nm, the iron carbide layer has a thickness of 60 nm, the nitrogen concentration of the iron nitride layer is 22% in mole percentage, and the carbon concentration of the iron carbide layer is 12% in mole percentage. A table comparing the characteristics of the soft magnetic thin film of the present example, a monolayer film of iron nitride having a nitrogen concentration of 16% by mole percentage and an iron carbide single layer film having a carbon concentration of 12% and 25% by mole percentage, respectively. Is.

In Table 1, the relative permeability is the value at 20MHz,
The weather resistance is represented by the ratio of the saturation magnetic flux density of the thin film after standing for 200 hours in a 3% salt spray to the saturation magnetic flux density before standing.

As is clear from Table 1, in this embodiment, it is possible to realize a soft magnetic thin film having high saturation magnetic flux density, magnetic permeability and durability which cannot be obtained by a single layer film.

Table 2 shows that the iron nitride layer has a thickness of 5 nm and the iron carbide layer has a thickness of 60 n.
In a soft magnetic thin film in which the carbon concentration of the iron carbide layer is 12% by mole percentage, the nitrogen concentration of the iron nitride layer is 22% by mole percentage,
9 is a table showing soft magnetic characteristics and weather resistance when the nitrogen concentration is changed from 4.7% to 22.0% in terms of molar percentage.

In Table 2, the weather resistance is represented by the ratio between the saturation magnetic flux density of the thin film after standing for 200 hours in a 3% salt water spray and the saturation magnetic flux density before standing.

As is clear from Table 2, an iron nitride layer having a film thickness of 5 nm,
In a multilayer film of an iron carbide layer having a carbon concentration of 60% and a carbon concentration of 12% in terms of mol percentage, a magnetic thin film having good soft magnetic properties when the crystal structure of the iron nitride layer is mainly composed of γFe ₄ N. Can be realized.

3, 4, and 5 show the saturation magnetic flux density, the coercive force, and the coercive force when the thickness of the iron nitride layer was fixed to 5 nm and the thickness of the iron carbide layer was changed from 0.7 nm to 5000 nm, respectively. It is the figure which showed the change of relative permeability in 20MHz. At this time, the crystal structure of the iron nitride layer contains γFe ₄ N as a main component, and the carbon concentration in the iron carbide layer is 12% in terms of molar percentage.

As is clear from FIGS. 3, 4, and 5, γFe
_{When an} iron nitride layer having a thickness of 5 nm and containing ₄ N as a main component and an iron carbide layer having a carbon concentration of 12% in terms of mole percentage are laminated and the thickness of the iron carbide layer is larger than 2 nm and smaller than 1100 nm. It is possible to realize a magnetic thin film having excellent soft magnetic characteristics.

Figures 6, 7, and 8 show the saturation magnetic flux density, coercive force, and coercive force when the thickness of the iron nitride layer was fixed to 60 nm and the thickness of the iron nitride layer was changed from 0.5 nm to 4000 nm, respectively. 20MHz
It is a figure showing change of relative permeability in. At this time, the crystal structure of the iron nitride layer contains γFe ₄ N as a main component, and the carbon concentration in the iron carbide layer is 12% in terms of molar percentage.

As is clear from FIG. 6, FIG. 7 and FIG. 8, an iron carbide layer having a film thickness of 60 nm and a carbon concentration of 12% in molar percentage,
When a layer of iron nitride containing Fe ₄ N as a main component is laminated, a magnetic thin film having good soft magnetic characteristics can be realized when the thickness of the iron nitride layer is larger than 0.5 nm and smaller than 200 nm.

Fig. 9, Fig. 10 and Fig. 11 show that the carbon concentration of the iron carbide layer was fixed by fixing the thickness of the iron nitride layer containing γFe ₄ N as the main component to 5 nm and the thickness of the iron carbide layer to 60 nm. 1.5% to 3% by mole
Saturation magnetic flux density, coercive force and 2 when changed to 7%
It is a figure showing change of relative permeability at 0 MHz.

As is clear from FIGS. 9, 10, and 11, when an iron carbide layer having a thickness of 60 nm and an iron nitride layer having a thickness of 5 nm and containing γFe ₄ N as a main component are laminated, When the carbon concentration of the iron carbide layer is more than 4% and less than 29% in terms of molar percentage, it is possible to realize a magnetic thin film having good soft magnetic characteristics.

FIG. 12 shows that the thickness of the iron carbide layer having a carbon concentration of 12% in terms of mole percentage was fixed to 5 nm, and the thickness of the iron nitride layer containing γFe ₄ N as a main component was changed from 0.5 nm to 4000 nm. FIG. 3 is a diagram showing the ratio of the saturation magnetic flux density of each thin film before standing and each saturation magnetic flux density after standing by allowing each thin film to stand in a 3% salt water spray for 200 hours.

As is clear from FIG. 12, the film thickness is 5 nm and the molar percentage is 1
When an iron carbide layer having a carbon concentration of 2% and an iron nitride layer containing γFe ₄ N as a main component are laminated, a magnetic thin film having good weather resistance is formed when the iron nitride layer has a thickness of 3 nm or more. Can be realized.

Fig. 13 shows that the iron carbide layer has a thickness of 60 nm and the iron nitride layer mainly composed of γFe ₄ N is fixed at a thickness of 5 nm, and the carbon concentration of the iron carbide layer is 1.5 to 37% in terms of molar percentage. FIG. 6 is a diagram showing the ratio of the saturation magnetic flux density of each thin film before standing and each saturation magnetic flux density after standing by allowing each of the thin films changed to 3% salt water spray for 200 hours.

As is clear from FIG. 13, an iron carbide layer having a film thickness of 60 nm,
When a film thickness of 5 nm and an iron nitride layer containing γFe ₄ N as a main component are laminated, a magnetic thin film with good weather resistance is realized when the carbon concentration of the iron carbide layer is 10% or more by mole percentage. be able to.

From the above results, layers of iron carbide having a C concentration of 4 to 35% by mole percentage and layers of iron nitride containing γFe ₄ N as a main component are alternately arranged, and the thickness of a single layer of iron carbide is By setting the thickness of the iron nitride single layer to 3 to 1000 nm and the thickness of the iron nitride single layer to 0.6 to 2000 nm, it is possible to provide a soft magnetic thin film having both high durability and magnetic permeability and a high saturation magnetic flux density.

A magnetic head according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 14 is a sectional view of a part of the magnetic head of the second embodiment of the present invention. In FIG. 14, numeral 31 indicates that the surface is sufficiently polished.
It is a cleaned ceramic substrate. Reference numeral 32 is a soft magnetic thin film of the present invention, in which an iron carbide layer having a thickness of 60 nm and a carbon concentration of 12% in terms of mole percentage and an iron nitride layer having a thickness of 5 nm and containing γFe ₄ N as a main component are laminated. The number of laminated layers is 46 for iron carbide layers and 45 for iron nitride layers.

The soft magnetic thin film 32 is formed on the entire surface of the ceramic substrate 31 by a sputtering method, and then patterned into a predetermined magnetic core shape by an ion milling method or a wet etching method. 33, 34, and 35 are gap materials such as SiO ₂ , organic insulating layers, and conductor coils, which are sequentially deposited on the entire surface by a film-forming method such as a sputtering method.
It is patterned into a predetermined shape by an ion milling method or a wet etching method. 36 is 31
The same soft magnetic thin film is formed by the same number of layers.
37 is a protective film, which is an insulating layer such as Al ₂ O ₃ deposited on the entire surface.

The deposit shown in FIG. 14 configured as described above is cut into a predetermined shape, and the head tip side 39 is polished to remove the magnetic gap.
38 is formed to form one thin film magnetic head.

The magnetic characteristics of the above magnetic head were measured by a thin film formed on another substrate under the same conditions, and the saturation magnetic flux density was 1.
It was confirmed that 87 Tesla, the coercive force in the hard-to-magnetize direction was 0.24 Oe, and the relative permeability at 20 MHz was 4100, showing excellent characteristics.

Also, when the electromagnetic conversion characteristics of the above head were compared with those of a conventional cobalt-based amorphous alloy thin film head, it was confirmed that the reproduction output was improved by about 25%. Further, the magnetic head of this example was left in a constant temperature and humidity chamber of 60 ° C. and a relative humidity of 90% until the reproducing output of the head using a conventional cobalt-based amorphous alloy thin film was reduced by 30%. There was almost no change in the playback output.

As described above, according to the present embodiment, by using the soft magnetic thin film of the present invention for the magnetic permeable layer, the saturation magnetic flux density is as high as 1.87 Tesla, and a magnetic head having both high magnetic permeability and corrosion resistance is obtained. Can be provided.

A soft magnetic thin film according to a third embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing a layered structure of iron carbide, iron nitride, and a layer of a nonmagnetic material such as silicon oxide in the soft magnetic thin film of the third embodiment of the present invention. In FIG. 2, 21 is iron carbide, 22 is iron nitride, and 23 is a non-magnetic material such as silicon oxide.

In this example, an iron carbide layer having a film thickness of 60 nm and a carbon concentration of 12% in terms of molar percentage, and a film thickness of ₅ n with γFe ₄ N as a main component were used.
An iron nitride layer of m and a layer of silicon oxide having a thickness of 3 nm are laminated by 45 layers, respectively, and a thin film magnetic head exactly the same as that of the second embodiment is formed, and the electromagnetic conversion characteristics are It was confirmed that the reproduction output was further improved by 20% in the high frequency region when compared with the thin film head of the example.

In addition, the reproduction output of the head using a conventional cobalt-based amorphous alloy thin film is maintained in a constant temperature and humidity chamber at 60 ° C and 90% relative humidity.
When the magnetic head of this example was left to stand until it was lowered by 30%, the reproduction output of the magnetic head of this example showed almost no change as in the head of the second example.

EFFECTS OF THE INVENTION As described above, in the present invention, the C concentration is 4 to 35% in terms of molar percentage.
Iron carbide layers and iron nitride layers containing γFe ₄ N as a main component are alternately arranged, and the thickness of the iron carbide single layer is 3 to 1000 n.
m, by providing a structure in which the thickness of a single layer of iron nitride is 0.6 to 200 nm, the high permeability of the iron carbide layer and the high durability of the iron nitride layer complement each other, and It is possible to provide a soft magnetic thin film having a saturated magnetic flux density, a high magnetic permeability and durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing a layered structure of iron carbide and pure iron in the soft magnetic thin film of the first embodiment of the present invention, and FIG. 2 is carbonization in the soft magnetic thin film of the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing a layered structure of iron and pure iron, FIG. 3 is a graph showing the relationship between the film thickness of the iron carbide layer and the saturation magnetic flux density when the thickness of the iron nitride layer is fixed. The graph shows the relationship between the film thickness of the iron carbide layer and the coercive force when the thickness of the iron nitride layer is fixed, and Fig. 5 is the film of the iron carbide layer when the thickness of the iron nitride layer is fixed. FIG. 6 is a graph showing the relationship between the film thickness of the iron nitride layer and the saturation magnetic flux density when the thickness of the iron carbide layer is fixed, and FIG. 7 is a graph showing the change in thickness and relative permeability. A graph showing the relationship between the thickness of the iron nitride layer and the coercive force when the thickness of the iron layer is fixed. Fig. 8 shows the thickness of the iron nitride layer when the thickness of the iron carbide layer is fixed and 20MH. Fig. 9 is a graph showing the relationship with the relative magnetic permeability at z, Fig. 9 is a lamination of an iron carbide layer with a thickness of 60 nm and an iron nitride layer with a thickness of 5 nm when the carbon concentration in the iron carbide layer is changed. Graph showing the relationship between the carbon concentration in the iron carbide layer and the saturation magnetic flux density of the film, Fig. 10 shows the iron carbide layer with a film thickness of 60 nm when the carbon concentration in the iron carbide layer was changed, and the film A graph showing the relationship between the carbon concentration in the iron carbide layer and the coercive force of a laminated film with a 5 nm thick iron nitride layer, Fig. 11 shows the film thickness when the carbon concentration in the iron carbide layer was changed. A graph showing the relationship between the carbon concentration in the iron carbide layer and the relative magnetic permeability of a laminated film of an iron carbide layer of 60 nm and an iron nitride layer of 5 nm in thickness, and Fig. 12 shows the thickness of the iron nitride layer. The thin film with the changed value is left standing in a 3% salt water spray for 200 hours, the ratio of the saturation magnetic flux density of each thin film before being left to the respective saturation magnetic flux density after being left, and the film thickness of the iron nitride layer, Table of relationships The graph in Fig. 13 shows the saturation magnetic flux density of each thin film before standing and the saturation magnetic flux density of each thin film in which the carbon concentration of the iron carbide layer was changed, left for 200 hours in 3% salt spray. FIG. 14 is a cross-sectional view of a part of the magnetic head according to the second embodiment of the present invention, which is a graph showing the relationship between the ratio of and the carbon concentration of the iron carbide layer. 11 …… iron carbide, 12 …… iron nitride, 21 …… iron carbide, 22 …… iron nitride, 23 …… non-magnetic material such as silicon oxide, 31 …… ceramic substrate, 32 …… soft magnetic thin film of the present invention , 33 ... Gap material, 34 ... Organic insulating layer, 35 ... Conductor coil, 36 ... Same soft magnetic thin film as 32, 37 ... Protective film, 38 ... Magnetic gap,
39 …… Head tip.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-285406 (JP, A) JP 60-132305 (JP, A) JP 63-297569 (JP, A)

Claims (4)

[Claims] 1. An iron carbide layer having a C concentration of 4 to 35% in terms of mole percentage and an iron nitride layer containing γFe ₄ N as a main component are alternately arranged, and the thickness of a single iron carbide layer. Is 3 to 1000 nm, and the thickness of the iron nitride single layer is 0.6 to 200 nm. 2. An iron carbide layer having a C concentration of 8 to 25% in terms of mole percentage and an iron nitride layer containing γFe ₄ N as a main component are alternately arranged, and the thickness of a single iron carbide layer. Is 10 to 150 nm, and the thickness of the iron nitride single layer is 1 to 10 nm. 3. A magnetic head using the soft magnetic thin film according to claim 1 or 2 for at least a part of a magnetic permeable layer. 4. A magnetic head according to claim 3, wherein a non-magnetic layer is inserted in the soft magnetic thin film according to either claim (1) or (2).