JPH05217114A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To enhance S/N by specifying the relationship between the waveform at the frequency of transfer rate and the distance from the center of magnetic gap to the edge in the direction of thickness of a magnetic layer. CONSTITUTION:A magnetic layer 5 for forming a magnetic gap (g) is applied through a nonmagnetic gap spacer 7 onto a magnetic substrate 1 while opposing to a surface 6 which opposes to a magnetic recording medium, thus constituting a thin film magnetic head in which a magnetic circuit is established passing through the magnetic layer 5 and the magnetic substrate 1. Assuming the relative speed between the magnetic head and the magnetic recording head is V and the highest repeating frequency of digital magnetic recording or the half frequency of transfer rate is fs, a relationship of 1.06lambdas<b<1.61lambdas is set between the wavelength lambdas=V/fs and the distance (b) from the center of the magnetic gap (g) and the edge in the direction of thickness of the magnetic layer 5. According to the constitution, S/N of a reproducing head can be enhanced in digital magnetic recording by taking advantage of the beating effect in the frequency characteristics of the head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film type magnetic head having an electromagnetic induction type or a magnetoresistive effect type structure, and more particularly to a thin film type magnetic head used for reproducing digital magnetic recording.

[0002]

BACKGROUND ART thin-film magnetic heads, for example, an electromagnetic induction type thin film magnetic head, as shown in FIG. 1, SiO _2, Si ₃ on the magnetic substrate 1 made of M _n -Z _n ferrite, etc.
Conductor layer 3 to be a head winding through insulating layer 2 such as N ₄
Is deposited, and similarly SiO ₂ and Si ₃ N
_A magnetic layer 5 made of permalloy, sendust or the like is deposited so as to cross the conductor layer 3 via an insulating layer ₄ such as 4.

The front end of the magnetic layer 5 extends to the contact surface 6 with the magnetic recording medium, and between the front end and the magnetic substrate 1.
A magnetic gap g whose gap length is regulated by the thickness of the gap spacer layer 7 by interposing a gap spacer layer 7 made of SiO ₂ or the like having a required thickness,
It is formed so as to face the contact surface 6 with the magnetic medium.

The rear end of the magnetic layer 5 is, for example, directly connected to the substrate 1 and magnetically and densely coupled to the substrate 1.

In this way, a magnetic circuit consisting of the base 1-magnetic gap g-magnetic layer 5-base 1 is formed around the conductor layer 3, and the signal magnetic flux from the recording medium contacting at the contact surface 6 is generated from the magnetic gap g. It is applied to the above-mentioned magnetic circuit, and thereby an induced current is generated in the conductor layer 3, that is, the head winding, so that a reproduction signal is taken out.

In such a thin film magnetic head,
As shown in FIG. 2 in which the portion of the magnetic gap g is substantially linearly enlarged, the core length of one of the core front faces facing each other across the gap g of the magnetic circuit depends on the thickness of the magnetic layer 5. In order to determine, the core length is as short as about 0.1 to 10 μm, and its shape effect has an effect on its frequency characteristic, and its original frequency characteristic is the spacing shown by the broken line in FIG. A curve that decreases almost monotonously due to loss has a characteristic in which undulation occurs as shown by the solid line curve in FIG.

FIG. 4 shows the deviation of this waviness.
Now, the peaks of the first valley, second mountain, and second valley of this swell
F for each frequency of the point₁, F₂, F₃・ ・ ・ ・ ・ ・ And this
Convergence level axis of waviness (deviation
0) and the intersections with₀, F _a, F_b, F_c‥‥age,
The wavelengths corresponding to these frequencies are λ₁, Λ₂, Λ₃...
λ₀, Λ_a, Λ_b, Λ_cLet's say. These wavelengths are
The relative velocity v between the air head and the magnetic medium was divided by each frequency.
It becomes a value.

The above-mentioned undulation of the frequency characteristic is a phenomenon caused by the above-mentioned short core length in the thin film magnetic head. Therefore, in this thin film magnetic head, the detection mode is the electromagnetic induction type or the magnetic type. This phenomenon occurs regardless of the resistance effect type.

On the other hand, in digital magnetic recording, frequency characteristics mainly required as electromagnetic conversion characteristics of the magnetic recording medium and the magnetic head are the following two points.

(I) A sufficient S / N ratio should be obtained at the frequency f _m . (Ii) The frequency characteristic should be gently inclined at the frequency f _m .

Here, f _m is a frequency representative of a frequency band in which the highest S / N ratio is desired in digital magnetic recording, and f _m is (a) NRZ, NRZ (I) system modulation. Method or MF
In the case of the M and FM modulation method, the maximum repetition frequency f _max
(F _m = f _max ), and (b) when a modulation method with a high density ratio such as HDM, EFM, FEM, 3PM is adopted,

[0012]

[Equation 1] And

[0013]

SUMMARY OF THE INVENTION The present invention improves the electromagnetic conversion efficiency for magnetic recording on a recording medium in a thin film type magnetic head.
This is what is required to obtain such characteristics.

[0014]

That is, in the present invention, the core length of the magnetic layer in the thin film magnetic head, that is, the distance b from the center of the magnetic gap to the edge of the magnetic layer in the thickness direction, and the frequency The electromagnetic conversion efficiency, that is, the output is improved by specifying the distance b while paying attention to the relationship with the undulation of the characteristic.

In the present invention, as shown in FIGS. 1 and 2, a magnetic gap g is formed by interposing a non-magnetic gap spacer layer 7 on the magnetic substrate 1 so as to face the contact surface 6 with the magnetic recording medium. In a thin-film magnetic head in which a layer 5 is deposited and a magnetic circuit passing through the magnetic layer 5 and the magnetic substrate 1 is formed, the relative speed between the magnetic head and the magnetic recording medium is set to v, and digital magnetic recording Maximum repetition frequency,
Or 1/2 of the bit rate frequency and wavelength λ _m = v / f _m when the f _m, the relationship between the distance b from the center of the magnetic gap g to a thickness direction of the edge of the magnetic layer 5, 1.06λ _m <b <1.61 λ _m (1)

[0016]

That is, in the present invention, from the frequency characteristics of FIGS. 3 and 4, from the point of improving the output with respect to the requirement of (i), f _m <f ₀ (2) Therefore, λ ₀ < _{λ m ‥‥ (2) '(} λ m = v / f m) or selected relationship, or _{f a <f m <f b} ‥‥ (3) _{Therefore, λ b <λ m <λ} a ‥‥ (3) 'is selected, and the output and the S / N are improved in this way.

As will be described in more detail, first, here, regarding the higher peaks of the third peak or higher in FIGS. 3 and 4, since the amplitude of the swell is attenuated to a higher order, the output is improved. Since the effect is small and the spacing between ridges and valleys is narrow, the bandwidth that contributes to output improvement is small, and the use of undulations is not advantageous, so it is excluded from the third peak and above. is there.

Now, as shown in FIG. 2, the magnetic layer 5 on the front end face of the magnetic layer 5 from the center of the magnetic gap g.
Let b be the distance to the outer edge e in the thickness direction of
The distance each position of waviness in FIG. 4 for b _{(frequency) f 0, f 1, f} a, f 2, f b, the relationship of f ₃ is as shown in Figure 5 in curves 51-56.

Then, similar distance b and each wavelength λ ₀ ,
The relationships with λ ₁ , λ _a , λ ₂ , λ _b , and λ ₃ are the lines 61 to 66 in FIG. 6. In this case, v = 4.8 cm / sec.

In the present invention, paying attention to the relationship between the distance b and the frequency and wavelength of the swell in FIGS. 5 and 6, the above expressions (2) and (2) ', (3) and (3) are given. The expression 'is set by specifying the distance b.

That is, in the present invention, the above (2)
The thickness of the magnetic layer forming the above-mentioned magnetic circuit, that is, the front end face of the magnetic layer from the center of the magnetic gap, is obtained so that the relationship of the equation ((2) ′) or the equation (3) ((3) ′) is obtained. The distance b to the outer edge portion at is selected by the above equation (1).

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIG. 1, a magnetic gap g is formed on a magnetic substrate 1 facing a contact surface 6 with a magnetic recording medium by interposing a non-magnetic gap spacer layer. In a thin-film magnetic head, in which the layer 5 is deposited and a magnetic circuit passing through the magnetic layer 5 and the magnetic substrate 1 is constructed, the relative speed between the magnetic head and the magnetic recording medium is as described above. v and, up to repeat the wavelength lambda _m = v / f _m and the thickness direction of the edge of the magnetic layer from the center of the magnetic gap when the half of the frequency of the frequency or the transfer rate and f _m of the digital magnetic recording Distance b
And the relation is 1.06λ _m <b <1.61λ _m (1). At this time, as is clear from FIG.
The above formulas (2) ((2) ′) and (3) ((3) ′) are satisfied. Now, for example, in the case of f _m = 50 kHz, when the relative velocity v with the magnetic medium is v = 4.76 cm / sec, λ _m = 0.952 μm. In this case, in FIGS. 5 and 6, the frequency is 50 kHz and the wavelength is 0.95.
When the intersections of the respective curves are found at 2 μm, the relationship is 1.01 μm <b <1.53 μm, that is, the relationship of the equation (1). Thus, when the distance b is specified, the S / N is improved. Incidentally, 71 in FIG.
Is a frequency characteristic curve when b = 1.0 μm, and a curve 72 shows the deviation of the waviness component. F _m = 50
The relationship of f _m = f _a is obtained at kHz.

[0023]

As described above, according to the present invention, the S / N ratio of the reproducing head in digital magnetic recording can be improved by effectively utilizing the effect of the frequency characteristic undulation in the thin film magnetic head. It is a thing.

[Brief description of drawings]

FIG. 1 is an enlarged schematic cross-sectional view of an example of a thin-film magnetic head used for explaining the present invention.

FIG. 2 is an explanatory diagram of a main part of the magnetic head of FIG.

FIG. 3 is a frequency characteristic curve diagram.

FIG. 4 is a diagram showing a waviness component.

FIG. 5 is a diagram showing the relationship of the frequency in the frequency characteristic to the distance from the center of the magnetic gap of the magnetic layer to the edge portion.

FIG. 6 is a diagram showing the relationship of the wavelength in the frequency characteristic with respect to the distance from the center of the magnetic gap of the magnetic layer to the edge portion.

FIG. 7 is a frequency characteristic curve diagram for explaining an example of a magnetic head according to the present invention.

[Explanation of symbols]

1 magnetic substrate 5 magnetic layer 7 non-magnetic gap spacer layer that regulates the gap length of the magnetic gap g

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[Procedure amendment]

[Submission date] October 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

[Action] That is, in the present invention, the frequency characteristic of FIG. 3 and FIG. 4, the in terms of improvement in output in response to a request _{(i), f a <f} m <f b ‥‥ (2) Thus, λ _b <λ _m <λ _a (2) ', and thus the output and the S / N are improved.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

In the present invention, focusing on the relationship between the distance b and the frequency and wavelength of the swell in FIGS. 5 and 6, the above expressions (2) and (2) 'are set by specifying the distance b.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

That is, in the present invention, the above (2)
In order to obtain the relationship of the equation ((2) ′), the thickness of the magnetic layer forming the above-mentioned magnetic circuit, that is, the distance b from the center of the magnetic gap to the outer edge portion of the front end face of the magnetic layer is defined by the above ( Select according to formula 1).

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIG. 1, a magnetic gap g is formed on a magnetic substrate 1 facing a surface 6 facing a magnetic recording medium by interposing a non-magnetic gap spacer layer. In a thin-film magnetic head, in which the layer 5 is deposited and a magnetic circuit passing through the magnetic layer 5 and the magnetic substrate 1 is constructed, the relative speed between the magnetic head and the magnetic recording medium is as described above. v and, up to repeat the wavelength lambda _m = v / f _m and the thickness direction of the edge of the magnetic layer from the center of the magnetic gap when the half of the frequency of the frequency or the transfer rate and f _m of the digital magnetic recording Distance b
And the relation is 1.06λ _m <b <1.61λ _m (1). At this time, as is clear from FIG.
The above expressions (2) and ((2) ') are satisfied. Now, for example, f _m
= 50 kHz, when the relative velocity v = 4.76 cm / sec with respect to the magnetic medium, λ _m = 0.952 μ
m. In this case, the frequency is 5 in FIGS.
When the intersection points in the respective curves are obtained at 0 kHz and a wavelength of 0.952 μm, it is 1.01 μm <b <1.53 μm, that is, the relationship of the equation (1) is obtained, and when the distance b is specified in this way, the S / N is improved. Is planned. Incidentally, 71 in FIG.
Is a frequency characteristic curve when b = 1.0 μm, and a curve 72 shows the deviation of the waviness component. F _m = 50
The relationship of f _m = f _a is obtained at kHz.

Claims (1)

[Claims] 1. A magnetic layer forming a magnetic gap is deposited on a magnetic substrate facing a surface facing a magnetic recording medium by interposing a non-magnetic gap spacer layer, and passes through the magnetic layer and the magnetic substrate. In a thin film magnetic head having a magnetic circuit, the relative speed between the magnetic head and the magnetic recording medium is v, and the maximum repetition frequency of digital magnetic recording or a frequency half the transfer rate is f. wavelength at the time of the _{m λ m}
= V a / f _m, the relationship between the distance b from the center of the magnetic gap to the thickness direction of the edge of the magnetic layer, 1.06
λ _m <b <thin film type magnetic head, characterized in that selecting the 1.61λ _m.