JPH02208813A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To reduce difference between the conversion efficiency of two cores by specifying a head opening angle made between the central direction of respective magnetic path of both cores and the hard axis of a magnetic material which comprises the magnetic path and is formed as a magnetic film. CONSTITUTION:In each of both cores, directions connecting a track width center 3a to the center 4a of a bridge part 4 between upper and lower magnetic films are assumed as magnetic path directions 5, 5. Also, an angle theta made between the magnetic path direction and a perpendicular N(fitted in hard axis) drawn on a confronting plane with a recording medium in an interval center between both cores is set as the opening angle, and it is set at the angle less than 25 deg.. Thereby, it is possible to obtain a two-channel type thin film magnetic head with satisfactory characteristic with low cross-talk.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film magnetic head. More specifically, the present invention relates to a two-channel thin film magnetic head used for recording and reproducing still images and the like.

[Prior art]

For recording and reproducing still images, etc., a magnetic material having -axis magnetic anisotropy was used as a magnetic film. Consisting of two cores2
Channel type thin film magnetic heads have been used conventionally.

Japanese Patent Application Laid-Open No. 80-45912 discloses that, in order to improve the core conversion efficiency of this type of thin film magnetic head and to reduce crosstalk between each core, a magnetic yoke is provided between adjacent magnetic yokes arranged symmetrically. A two-track type thin film magnetic head is disclosed in which the distance between the two tracks increases as the distance from the magnetic gap increases, and the magnetic legs protrude from the magnetic legs. As this embodiment, the shape of the magnetic core is shown in FIG. 7 of the accompanying drawings of the present application. This ensures the yoke cross-sectional area, which tends to be insufficient in magnetic thin films, and satisfies the dimensional constraints between the gaps between two cores, while also preventing crosstalk that occurs due to magnetic flux jumping between two cores. There is.

[Problem to be solved by the invention]

The magnetic thin film head disclosed in Japanese Patent Application Laid-Open No. 80-45912 is a two-channel magnetic thin film head that is effective in improving conversion efficiency and preventing slow talk, but as is clear from FIG. The core shape is quite complex, and there are many factors that define the characteristics, making it difficult to uniquely control the characteristics from such a shape design. Therefore, in order to obtain a product with the desired characteristics, the only way to obtain it is to change the design and repeat tests through trial and error.2 For example, it is difficult to predict what characteristics will be obtained by partially changing the shape. Furthermore, there is a possibility that the yield rate will decrease due to deviation from the required characteristics.

In view of this, the present invention can be controlled by simple factors, satisfies the dimensional requirements between channels,
Another object of the present invention is to provide a two-channel thin film magnetic head with low crosstalk and good characteristics.

[Means to solve problems]

The object of the present invention is that a pair of thin film magnetic cores made of magnetic materials having substantially the same magnetic properties are arranged symmetrically with respect to a perpendicular to a surface facing a recording medium.

the center direction of a magnetic path connecting the center of each track width of the re-magnetic core and the center of the upper and lower magnetic core connecting portion of the magnetic core;
This is achieved by characterized in that the head opening angle formed between the magnetic material constituting the magnetic core and the axis of hard magnetization is 25 degrees or less (claim 1).

The knowledge of the present invention is as follows.

The dimensional conditions for a two-channel type thin film magnetic head are as follows: 1. For example, the center distance between both channels must be approximately 100 μl or less from the perspective of high-density recording, and considering the width required for the track of approximately 60 μm, the center distance between both channels must be approximately 100 μl or less. The separation distance between the channels is approximately 40 μm or less. Under these conditions, in addition to improving magnetic conversion efficiency and reducing crosstalk, the device requires that the conversion efficiency of both cores be substantially the same. Therefore, it is necessary to manufacture the two cores so that the difference in conversion efficiency is 2 dB or less between the two cores. From the viewpoint of controlling the difference to be small in this way, it is desirable that the shape be as simple as possible in order to eliminate the influence of shape-dependent factors as much as possible.

On the other hand, the difference in efficiency between the two cores actually manufactured is simply due to the difference in the outer shape of the cores.

One possible method is based on the difference between the direction of the easy axis of magnetization (or the direction of the hard axis of magnetization) and the direction of the magnetic path. It has been confirmed through experiments in the present invention that the angular error of the latter can be suppressed to within 5" from the viewpoint of manufacturing technology. The former is extremely small by making the core shape substantially band-shaped. It is possible (Claim 2).

Now, from the viewpoint of preventing crosstalk, it is advantageous to make these magnetic paths as far away from the gap as possible as described in the above-mentioned publication.

However, even in this case, the difference in efficiency between both cores is 2d
It is necessary to keep it within B, and it is necessary to find the necessary conditions for this. Therefore, the applicant clarified this condition as follows.

First, we will investigate which conditions change the efficiency of the core. Gear lug length ig and core length Jc depicted in Figure 5
Let us consider a ring model magnetic core having a gap section cross-sectional area Ag and a core section cross-sectional area Ac.

The conversion efficiency α of this core is It is expressed as α-Rg/(Rg+Rc).

Here, Rg and Re represent the magnetic resistance of the gap part and the core part, respectively, and the magnetic permeability of each part is μ0.
If μC, then Rg=Jg/μoAg.

Rc-AC/μcAc So, in the end, α is.

a=Ag/[, eg +J! c / (, crc
(Ac/Ag)l]-μC (However, the relative magnetic permeability of the core portion is assumed to be μa --μ0).

Now, with the above formula obtained with this model, fg-0,2tin,
Ac/Ag=2. j! c When set to −100 μm.

If we plot α as a function of 10, we get Figure 2. Here, μC is μ', which is a symbol commonly used from the viewpoint of magnetic permeability of magnetic materials. The conversion efficiency α in the core changes in this way depending on the relative magnetic permeability μ′/μ0 (=, C<C).

Although this relative magnetic permeability μ'/μ0 varies depending on two different factors in an actual core, it was determined experimentally as a function of the angle between the easy axis of the magnetic material and the magnetic path direction in accordance with the purpose of the present invention. This is shown in Figure 3.

The material used in the experiment was a CoNbZr alloy film.
The dependence of magnetic permeability μ' and loss coefficient (tan δ) on the angle formed between the easy axis direction of magnetization and the magnetization direction of the NbZr alloy film was determined through experiments. The composition of each component of the alloy film used in the experiment was Co N b Z r
(at%).

88.4 g, 0 3.8 Using this material, 100 μm width, 30 mm length, 12-
A strip sample of different thickness was prepared. These are created by creating a pattern on the substrate by ion milling, followed by heat treatment in a magnetic field (1
After treatment at 350°C for 1 hour in the direction of the easy axis at kOe, treatment at 310°C for 75 minutes at 1 kOe in the direction orthogonal to the easy axis)
It was manufactured by applying. Measurements were carried out at various frequencies, and measurements were taken up to a maximum of 10 MHz, taking into consideration the frequencies normally used in still cameras and the like (Fig. 3).

obtained from this experiment. Relative magnetic permeability μ′/μ of strip core
The angular dependence of 0 is most pronounced in lOMIIz. This is considered to be because the contribution of domain wall movement to the magnetization process increases as the direction is closer to the easy axis, and this domain wall movement cannot follow the signal frequency at higher frequencies. FIG. 4 shows the measurement data of the frequency characteristics of the relative magnetic permeability of this belt-shaped core by changing the angle between the easy axis direction and the magnetic path direction.

By combining FIG. 2 and FIG. 3, the magnitude of the magnetic conversion efficiency α caused by manufacturing errors in the core angle is determined and viewed. In the head schematically shown in FIG. 1, for example, if the head opening angle is set to 15'' from the perspective of crosstalk, then
1 due to the 5″ angle error that must be allowed for during manufacturing.
The head opening angles of both cores are lO″ and 20°, respectively (
(See Figure 6). From Figure 3, the corresponding l0LIIZ
The relative magnetic permeability μ'/μ0 is 820 and 430, respectively. According to FIG. 2, the corresponding a is each 0.56
and 0.631: Nari, , :(7) difference Iha 20
i ((1,83/0.58)-L, 0 (dB), which is within the 2 dB required by the device and satisfies the required characteristics.

Next, when the head opening angle is set to 30'', the difference in efficiency α due to the manufacturing angle error of 5'' is similarly shown in Figures 2 and 3.
This value is determined based on the figure and reaches 2.3 dB, which is the request from the equipment. This goes against the requirement of 2 dB or less. Therefore, it is not possible to set the head opening angle to 30@. If the head opening angle corresponding to the request from the device is within 2 dB, the set angle will be within 25 degrees.

As described above, the present invention can determine the head opening angle of a two-channel thin-film magnetic head by measuring changes in magnetic permeability due to angular errors in head manufacturing and the angle between the hard magnetization axis of the magnetic material and the magnetic path direction. Find the upper limit value, and from this,
This makes it possible to manufacture a head that can satisfy required characteristics even if unavoidable manufacturing angle errors occur.

[Effect]

In the configuration of the present invention, by setting the angle between the hard magnetization axis of the magnetic material of the core film and the magnetic path direction to be 25 degrees or less, the difference between the two cores due to the difference in the head opening angle due to manufacturing errors. The difference in efficiency is kept within 2 dB.

〔Example〕

An example of a thin film magnetic head according to the present invention is shown in FIG. Note that FIG. 1A is a plan view seen from the upper magnetic film side, and FIG. 1B is a cross-sectional view thereof.

In the figure, a non-magnetic material (Zn ferrite) was used as the substrate material. Both the upper core film and the lower core film were Co N b Z r (at%) 88.
4 8.0 3.0. The characteristics of the magnetic material that makes up the core film are Hk (anisotropic magnetic field) = 3.50e, Bs (saturation magnetic flux density)
-10.5 kG, and the film thickness is 12 μm. The total length of each magnetic path is 130 μl, the core width is 100 μm, )
The rack width is 60 mm, and the distance between both cores at the gap portion is 40 .mu.m. Furthermore, in each of the two cores, there is a bridge portion 4 between the track width center 3a and the upper and lower magnetic films.
The direction connecting the center 4a of the two cores is defined as the magnetic path direction (5, 5), and a perpendicular line N (not aligned with the axis of difficult magnetization) drawn from the magnetic path direction to the surface facing the recording medium at the center of the interval between both cores. The head opening angle is the angle θ between the
It is set as °.

In FIG. 1, the upper magnetic film 1 and the lower magnetic film 1' have substantially the same planar shape, and have a substantially width of 100 μm as described above.
- is arranged on the substrate in the form of a rectangle, and the non-magnetic film 5IO2
are separated from each other by The core width is determined from the perspective of securing the necessary cross-sectional area. Furthermore, since it is sufficient that the magnetic path is substantially strip-shaped, there is a high degree of freedom in the core shape itself. Further, in the two embodiments, both the upper and lower magnetic films have the same shape, but they do not necessarily have to be the same, and the lower magnetic film may be formed over the entire surface of the substrate.

Bridge portions 4 of upper and lower magnetic films in each core
and the center 3a of the gap 3 in the track width direction.
The magnetic path center line 5 connecting the two cores forms an angle θ (20°) with the center line N of the spacing between both cores. However, the centerline N and the core itself are substantially parallel. The characteristics are better than forming the core in a strip shape parallel to the center direction of the magnetic path.

The coil 2 surrounds the bridge portion 4, and the number of turns thereof is determined to be seven.

The width of gap 3 is determined to be 80 - in order to match the track width on the recording medium, but the slope required to transition from this gap to the wide core part, that is, the gap 3 is far from the center line N. slope 9 transitioning to the side core side 8
The angle α between the track width direction and the track width direction is about 30''.

A straight line portion lO between the gap 3 and the slope 9 is set to the same value corresponding to a gap depth of 5 gm.

〔Effect of the invention〕

In the configuration of the present invention, the head opening angle formed between the center direction of the magnetic path of each of the two cores and the hard magnetization axis of the magnetic material forming the magnetic path and formed as a magnetic film is set within a predetermined range. By doing this, the difference in efficiency between the two cores can be controlled to below a predetermined value.

The basic design of both cores can be freely designed based on various factors such as the shape of the cores, and the difference in conversion efficiency between the nine cores can be basically reduced (Claim 1).

In other words, by setting the head opening angle of one core to 25 degrees or less, even if we take into account the unavoidable manufacturing error of 5" for the difference in efficiency between nine cores, it is still possible to Since it is possible to meet the requirement of a difference in efficiency of 2 dB or less, it is possible to manufacture a double head suitable for mass production in which the characteristics of the nine cores are well matched.

Further, according to the present invention, both cores are substantially band-shaped,
This can also be parallel to the perpendicular line drawn to the surface in contact with the recording medium, which can reduce factors that depend on the shape or reduce its influence, resulting in a great advantage in designing a core with desired characteristics ( Claim 2).

[Brief explanation of the drawing]

FIG. 1A is a schematic diagram of the core of a two-channel thin film magnetic head according to an embodiment of the present invention, and FIG. 1B is a sectional view (portion) taken along the line BB in FIG. 1A. Figure 2 shows the relative permeability of the magnetic material and the core efficiency α of the magnetic head.
A graph showing the relationship between. FIG. 3 is a graph of the relationship between the angle between the axis of easy magnetization and the direction of magnetization of a magnetic material, the relative magnetic permeability μ'/μ0, and the loss coefficient tanδ, obtained through actual measurements at different measurement frequencies. FIG. 4 is a graph in which the frequency characteristics of relative magnetic permeability were measured for a belt-shaped core by varying the angle θ between the axis of easy magnetization and the direction of magnetization. FIG. 5 is a schematic diagram showing a model of a magnetic core for determining the core efficiency of a magnetic head. FIG. 6 is an explanatory diagram regarding manufacturing errors in the head opening angle of the two-channel core. FIG. 7 is a schematic diagram of the core portion of a conventional two-track type thin film magnetic head. are shown respectively. Explanation of symbols 1.1'...Magnetic core 2...Coil 3...Gap 3a...Track width center to 4...Connection part (bulb 1) of upper and lower magnetic films, gap Part) 4a...Connection part of upper and lower magnetic films (button part) Center 5...Magnetic path center direction 6...Nonmagnetic film SiO□1
1...Substrate applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Asa Kato Figure 2 above is one volume (IL;/l'o) Figure 4 Peripheral frequency (MHz) Figure 5 Figure 6 Procedural amendment (voluntary) March 16, 1999

Claims (2)

[Claims] (1) A pair of thin film magnetic cores made of magnetic materials having substantially the same magnetic properties are arranged symmetrically with respect to a perpendicular to the surface facing the recording medium, and each track width of both magnetic cores is The head opening angle formed between the center direction of the magnetic path connecting the center and the center of the upper and lower magnetic core connecting portions of the magnetic core and the difficult-to-magnetize axis of the magnetic material constituting the magnetic core is 2.
A two-channel thin film magnetic head characterized by an angle of 5° or less. (2) A two-channel thin film magnetic head according to claim 1, wherein each magnetic core is formed into a band shape substantially parallel to the perpendicular line.