JPS62189610A - High frequency magnetic head - Google Patents

Abstract

PURPOSE:To reduce the effect of resonance loss at a high frequency and to prevent deterioration in the initial magnetic permeability, by providing an anti- ferromagnetic layer having a nail point higher than a room temperature into an amorphous magnetic layer and producing a magnetic head with use of a laminated head core while separating said amorphous layer containing the anti-ferromagnetic layer by means of a nonmagnetic insulated layer. CONSTITUTION:Such a magnetic head is produced by laminating plural pieces of the combination unit including an amorphous magnetic layer 6 formed with the thickness of its single layer set under the depth of the surface layer at a using frequency and an anti-ferromagnetic layer 8 having a nail point higher than a room temperature and provided into the layer 6 or on the surface of this layer 6. At the same time, the magnetic head uses a magnetic core using the nonmagnetic insulated layers 7 to separate those unit layers from each other. In such a way, the resonance loss is satisfactorily reduced. Then it is possible to secure the satisfactorily high efficiency of the magnetic head core even at a high frequency band.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laminated high frequency magnetic head using a soft magnetic material and used at high frequencies.

Conventional technology As soft magnetic materials for conventional magnetic helad cores, materials with high saturation magnetic flux density and high initial magnetic permeability (that is, low magnetic anisotropy) are suitable, such as permalloy, sendust, and various amorphous materials. Magnetic materials and ferrites have been used. In particular, the above-mentioned materials other than ferrite are usually metal materials with low resistivity, so when used as helad cores in high frequency bands, eddy current loss is large, and they are used as thin body or thin film magnetic materials. However, in particular, VTRs etc. aimed at recording high levels of bitterness
c) When considering the initial permeability loss in the frequency band above MHz, depending on the thickness of the magnetic material, the loss due to magnetic resonance absorption loss (natural resonance) may be more important than the above-mentioned eddy current loss. In particular, in amorphous soft magnetic thin films whose anisotropy has been significantly erased by heat treatment in a rotating magnetic field, etc., the internal magnetic field of the magnetic material itself is extremely small.
At relatively low frequencies, high-frequency losses due to natural resonance occur, resulting in a rapid decrease in initial permeability.

Figure 3a shows the specific resistance after heat treatment in a rotating magnetic field: ρ=1
20μΩ・clIl film thickness 4 mainly composed of co and Nb
Examples of frequency characteristics of the initial magnetic permeability μi of a thin film of a metal-metal amorphous alloy with a size of 1 m06 and a high frequency magnetic field from 100 KHz to 100 MH2 are shown for several samples.

In the same figure, for each initial permeability, the theoretical frequency limit value of a 4 μm film thickness having the above specific resistance value is shown at the skin depth (5kin depth) S = 2, ca.
The value m obtained from the following relationship is indicated by a broken line.

(Skin depth limit) From the same figure, it can be seen that in the 4 μm thick amorphous material mentioned above, the initial permeability deteriorates significantly in a frequency band considerably lower than the band where eddy current loss becomes a problem. Recognize.

On the other hand, from the natural resonance frequency (90MH2 for the sample in Figure 3a) estimated from the internal magnetic field Ha determined from the anisotropy energy and saturation magnetization values of the magnetic thin film, the above-mentioned rapid deterioration of the initial magnetic permeability is confirmed. , it was easily seen that this was due to resonance loss.

In this way, the magnetic material with the anisotropy removed is 10M
At high frequencies above Hz, even if the magnetic film is thick enough to take eddy current loss into consideration, the resonance loss of the magnetic material itself becomes a major problem, causing a decrease in initial permeability. This was a problem as a cause of loss in the amorphous magnetic herad core used in In particular, the anisotropy near the magnetic gap, where the magnetic permeability of the magnetic core has a large effect on the characteristics of the head,
The problem was that it remained significantly smaller due to heat treatment in a rotating magnetic field.

Problems to be Solved by the Invention The present invention solves the problem of first transmission by reducing the influence of resonance loss at high frequencies in a magnetic helad core made of a magnetic material with extremely low anisotropy as described above. The present invention provides a high frequency magnetic head that prevents deterioration of magnetic property.

In order to improve the above points, in particular near the magnetic gap, which has a large effect on the frequency characteristics of the magnetic core, or throughout the magnetic core,
By inducing anisotropy that does not drastically reduce the permeability in the magnetic flux direction of the magnetic core, the natural resonance frequency of the magnetic material is shifted to a higher frequency side, and as a result, the efficiency of the magnetic herad core at high frequencies is improved. The present inventors have already filed an application regarding a method for manufacturing a magnetic head.

The idea is based on the following principle.

In a resonant state (natural resonance state) in which no external magnetic field is applied to a magnetic material, the resonant frequency (angular frequency W = 2nf
) and the magnetic resonance magnetic field, there is a relationship of W = TH2L (HIL: internal anisotropic magnetic field, γ: rotational magnetic ratio). Although the initial magnetic permeability μm is high in amorphous magnetic materials,
The internal magnetic field Ha is extremely small. However, when magnetic anisotropy is induced in a material by some method, the newly generated internal magnetic field Hi is further added as an anisotropic magnetic field, so the resonance (angular) frequency becomes W' = ν(
Ha+Hi), and the resonant frequency extends to the higher frequency side by H1 (ie, w'>w).

In this way, when anisotropy is newly induced in an arbitrary direction with respect to the magnetic flux direction of the head core by some method, the above-mentioned effects can be expected.

However, at this time, some kind of heat treatment step or the like was required to induce anisotropy.

Means for Solving the Problems In order to prevent the formation of induced magnetic anisotropy, in the present invention, an antimagnetic material having a Neel point above room temperature is used in the amorphous magnetic layer, including the surface immediately above or below the amorphous magnetic layer. A ferromagnetic layer is provided, and an amorphous layer including the antiferromagnetic layer is laminated while being separated by a nonmagnetic insulating layer, and a magnetic head is constructed using a Radcore. When a ferromagnetic layer is created on a magnetic film, the effect of unidirectional anisotropy caused by (exchange) interaction from both interfaces is added, causing a change in the anisotropy of the amorphous film, resulting in the above effect. can be expected. however,
Since this interaction occurs only from the interface between the amorphous soft magnetic layer and the antiferromagnetic layer, it is important to increase the number of both interfaces as much as possible.
It is desirable to have a multilayer structure.

The foregoing is useful for example in the Journal of Applied Physics (J.

Mpp1. Phys,)s2(s)March 19
81, P2471) The magnetic head according to the present invention is based on the basic structure shown in FIG. Has a structure. In the figure, 1a is a nonmagnetic substrate, on which a magnetic core layer 2 having a structure as described later is formed. 1b is a non-magnetic substrate, which is arranged so as to sandwich the magnetic core layer 2 between the non-magnetic substrate 1&. 4 is a gap, and 6 is a winding window.

Hereinafter, the magnetic core layer 2 in each example will be explained in more detail with reference to FIG. 2. In addition, each figure in Figure 2 is as follows.
This is an enlarged view of the portion marked "mu" in FIG. 1.

Example 1 As shown in FIG. 1a, an amorphous soft magnetic thin film 6 is formed on a non-magnetic substrate 12L with a film thickness that takes into account the skin depth of the magnetic field at the operating frequency (i.e., less than the skin depth). Several layers are laminated with a non-magnetic insulating layer 7 made of 5i02 having a unit layer thickness of several thionic gestromes interposed therebetween. An antiferromagnetic film 8 made of a Feso'so film is inserted into this amorphous soft magnetic thin film θ to a thickness of approximately 1000 nm.

Due to such a laminated film structure, the frequency characteristic of the initial magnetic permeability of the amorphous soft magnetic film 6 is such that the resonance frequency is extended toward higher frequencies due to the induced anisotropy, as shown in Figure 3. This was confirmed. Also, by this method, 10MH!
The above-mentioned improvement in the efficiency of the herad core was observed in the head core configured as shown in FIG.

In the above example, one of the antiferromagnetic films with a Neel point above room temperature
Although Fe--Mn alloy is shown as an example, the above-mentioned effects will of course remain the same even if other antiferromagnetic films are used. In addition, the thickness of the single-layer amorphous magnetic layer including the antiferromagnetic layer is determined by laminating non-magnetic insulating layers in small thickness units relative to the skin depth considering eddy current loss at the operating frequency. Needless to say, it is necessary.

Note that introducing anisotropy by forming an extremely large number of multilayer films has the opposite effect because it lowers the initial magnetic permeability of the amorphous material.

Example 2 As shown in FIG. 2, an amorphous thin film 6 was laminated in the same manner as in Example 1, and an antiferromagnetic film made of Fe50"50 was added only on one surface of the amorphous soft magnetic film. In the head core using such a core, an improvement in the high frequency characteristics of μi as shown in FIG. 3 was also observed.

Example 3 As shown in FIG. 2C, the antiferromagnetic layer 8 (Fe50''!
)) A magnetic core layer including a repeating unit B was formed, consisting of an amorphous magnetic layer 6a containing the same and an amorphous magnetic layer 6b not containing the same separated by a nonmagnetic insulating layer y (5in2). . Even in a head core including such a core, an improvement in the high frequency characteristics of μi as shown in FIG. 3 was observed.

Effects of the Invention According to the present invention, 10M of high-density recording VTR heads, etc.
As a core material for a magnetic head used at high frequencies of H2 or higher, resonance loss can be sufficiently reduced even if a head core is heat-treated in a rotating magnetic field to improve the low-frequency permeability of the magnetic material. Even in such a high frequency band, the efficiency of the magnetic herad core can be made sufficiently high, making it extremely effective in practice.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a magnetic head according to an embodiment of the present invention, Fig. 2 is a sectional view showing an embodiment of the main parts of the magnetic head of Fig. 1, and Fig. 3a shows heat treatment in a rotating magnetic field. FIG. 3 is a frequency characteristic diagram of the initial magnetic permeability of the core magnetic material in the magnetic helad core according to the present invention. 11L, 1b...Nonmagnetic substrate, 2...
Magnetic core layer, 4...gap, 6...
Amorphous magnetic thin film, 7...Nonmagnetic insulating layer, 8...
...Antiferromagnetic film.

Claims (4)

[Claims] (1) An amorphous magnetic layer formed with a single layer thickness within the skin depth at the operating frequency, and an antiferromagnet with a Neel point above room temperature provided in or on the surface of each amorphous magnetic layer. 1. A high-frequency magnetic head characterized in that it is constructed using a magnetic core in which a plurality of combination units including a layer are laminated and each unit is separated by a non-magnetic insulating layer. (2) The high frequency magnetic head according to claim 1, wherein the antiferromagnetic layer is a Fe-Mn alloy film. (3) The high frequency magnetic head according to claim 1, wherein the nonmagnetic insulating layer is a SiO_2 film. (4) A high frequency magnetic head as described in which an amorphous soft magnetic layer including an antiferromagnetic layer and an amorphous soft magnetic layer not including the antiferromagnetic layer are separated by a nonmagnetic insulating layer.