JP2500572B2 - Thin film magnetic head - Google Patents

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]

2. Description of the Related Art As shown in FIG. 1, a thin film magnetic head, for example, an electromagnetic induction type thin film magnetic head, has SiO ₂ , Si ₃ on a magnetic substrate 1 made of Mn--Zn ferrite or the like.
Conductor layer 3 to be a head winding via insulating layer 2 such as N ₄
Is deposited and similarly SiO ₂ , 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 surface 6 facing the magnetic recording medium, and a gap made of SiO ₂ or the like having a required thickness is formed between the front end and the magnetic substrate 1. A magnetic gap g in which the spacer layer 7 is interposed and the gap length is regulated by the thickness of the gap spacer layer 7
Are formed so as to face the surface 6 facing 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 is formed by the base 1, the magnetic gap g, the magnetic layer 5, and the base 1 around the conductor layer 3, and the signal magnetic flux from the storage 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, the core length is appropriately short from 0.1 to 10 μm, and its frequency effect is affected by its shape effect, and its original frequency characteristic is the spacing shown by the broken line in FIG. The curve that decreases almost monotonously due to the loss has a characteristic in which undulation occurs as shown by the curve shown by the solid line in the figure.

FIG. 4 shows the deviation of this waviness.
Now, let the frequencies of the vertices of the first valley, the second peak, and the second valley of the swell be f ₁ , f ₂ , f ₃ , ..., respectively, and the convergence level of the swell on both sides of these valleys and mountains. The intersections with the axes (deviation 0) are defined as f ₀ , f _a , f _b , f _c, ...
₁ wavelength corresponding to these frequencies _{λ, λ 2, λ 3 ‥‥} ,
Let λ ₀ , λ _a , λ _b , λ _c . These wavelengths are values obtained by dividing the relative velocity v between the magnetic head and the magnetic medium by each frequency.

Since 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, the detection mode of this thin film magnetic head 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 a magnetic recording medium and a magnetic head are the following two points.

(I) A sufficient S / N ratio should be obtained at the frequency f _m . (Ii) The rate of output fluctuation is small at the frequency f _m , that is, the frequency characteristic is gentle.

[0011] Here, the frequency representing a frequency band that has the highest S / N ratio in digital magnetic recording and f _m is desired, this f _m is, (a) NRZ, NRZ ( I) based 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,

[Equation 1] And The requirement (ii) above is particularly strongly demanded because of simplification of the equalizer circuit.

[0012]

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.

[0013]

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 described above, that is, the output is improved by specifying the distance b while paying attention to the relationship with the undulation of the characteristic.

According to 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 magnetic layer 5 that forms the magnetic layer 5 is deposited, and a magnetic circuit passing through the magnetic layer 5 and the magnetic substrate 1 is configured, the relative speed between the magnetic head and the magnetic recording medium is v, the wavelength λ _m = v / f _m at the time of the maximum repetition frequency or half the frequency of the transfer rate, the digital magnetic recording and f _m, from the center of the magnetic gap g to a thickness direction of the edge of the magnetic layer 5 The relationship with the distance b is selected as 0.83λ _m <b <1.33 λ _m (1).

[0015]

In other words, according to the frequency characteristics of FIGS. 3 and 4, in the present invention, the slope (derivative coefficient) of the swell deviation is positive, that is, the output increasing tendency is used in response to the requirement (ii). focusing on it is advantageous, which has a _{f 1 <f m <f 2} ‥‥ (2) hence _{λ 2 <λ m <λ 1} ‥‥ (2) ', the frequency characteristic in this way To be flattened. As will be described in more detail, first, in FIGS. 3 and 4, regarding higher-order peaks higher than the third peak, the amplitude of the swell is attenuated to a higher order, so that the effect of improving the output is obtained. Since the width is small and the interval between the ridges and valleys of the undulations is narrowed, the bandwidth that contributes to the improvement of the output becomes small, and the utilization of the undulations is not advantageous, so that the second peaks and below are targeted.

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. The similar distance b and the respective wavelengths λ ₀ , λ ₁ , λ _a , λ ₂ , λ _b , and λ ₃ are shown by the lines 61 to 66 in FIG. In this case, v = 4.8 cm / sec.

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.

That is, the distance b from the center of the magnetic gap to the outer edge of the front end face of the magnetic layer is selected.

That is, according to the present invention, the thickness of the magnetic layer constituting the above-mentioned magnetic circuit, that is, the center of the magnetic gap and the front side of the magnetic layer, are obtained from the relations of the above equations (2) and (2) '. The distance b to the outer edge portion on the end face is selected by the above equation (1).

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a magnetic layer 5 is formed on a magnetic substrate 1 so as to face a surface 6 facing a magnetic recording medium and a magnetic gap 5 is formed by a nonmagnetic gap spacer layer 7 interposed. In a thin-film magnetic head in which 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 v,
Wavelength λ _m = v where f _m is the maximum repetition frequency of digital magnetic recording or half the transfer rate
The relationship between / f _m and the distance b from the center of the magnetic gap g to the edge in the thickness direction is 0.83λ _m <b <1.33λ _m (1). As is clear from FIG. 6, (2) and (2) ′ are satisfied.

Therefore, when such a structure is adopted,
In the swell of frequency characteristics, its differential coefficient is substantially positive.
Use of parts is done. Now, for example, f_m= 50 kHz
As for the case, the relative velocity v to the magnetic medium is v = 1.7.
At 6 cm / sec, λ_m= 0.952 μm. this
In the case of FIG. 5 and FIG. 6, the frequency is 50 kHz and the wave
Find the intersection of each curve with a length of 0.952 μm
And 0.79 μm <b <1.27 μm, that is, the relationship of the equation (1), and the distance b is specified in this way.
This frequency f _mThe frequency characteristic is gentle
The kana characteristic is obtained and a high output is obtained.
Reference numeral 71 in FIG. 7 is a frequency characteristic when b = 1.0 μm.
The curve 72 shows the deviation of the waviness component.
So f_m= F at 50 kHz_m= F_aGot the relationship
Have been.

[0022]

As described above, according to the present invention, the output of a reproducing head in digital magnetic recording can be improved by effectively utilizing the effect of the frequency characteristic waviness in a thin film type magnetic head. is there.

[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 a relationship of frequency in frequency characteristics with respect to a distance from a center of a magnetic gap of a magnetic layer to an edge portion.

FIG. 6 is a diagram showing a wavelength relationship.

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

Claims (1)

(57) [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 when _m is 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, 0.83
λ _m <b <thin film type magnetic head, characterized in that selecting the 1.33λ _m.