JPH06187616A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To suppress the generation of noises including the Barkhausen noises, etc., especially when the long wavelength recording signals like and analog compact cassette tape, etc., are reproduced by a magneto-resistance effect type thin film magnetic head. CONSTITUTION:In regard of the structure of the magneto-resistance effect type thin film magnetic head, the gap length of a magnetic coupling part between each of upper yokes 2 and 3 and an MR element 1 is set at 0.5-2.0mum when both yokes 2 and 3 are overlapping the element 1. Meanwhile, the gap length is set at 0.01-1.5mum when the yokes 2 and 3 are not overlapping the element 1. In such a way, the magnetic interaction can be optimized between the yokes 2 and 3 and the MR element 1 so that such noises including the Barkhausen noises, etc., caused by the reproduction characteristic can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a signal magnetic field to a magnetic core made of a ferromagnetic thin film, ferrite, etc. and a ferromagnetic thin film having uniaxial anisotropy, and uses it as an electric resistance change in the easy axis direction of magnetization. The present invention relates to the structure of a thin film magnetic head that includes a magnetoresistive effect element (hereinafter referred to as an MR element) for detecting and detects a signal recorded on a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, an MR head receives a signal magnetic field written on a magnetic recording medium such as a magnetic tape to generate an M
The magnetization direction inside the R element changes, and the resistance change of the MR element according to the change in the magnetization direction is extracted as an external output.

As described above, the MR head is a magnetic flux response type head and can reproduce the signal magnetic field without depending on the speed of the magnetic recording medium.

Further, the MR head can be easily highly integrated and have a large number of elements by applying a semiconductor fine processing technique. Therefore, a magnetic head for reproducing a fixed head type digital audio for high density recording. It is used as such. Further, in recent years, such a magnetoresistive thin film magnetic head has been used for reproducing an analog tape.

In such a magnetoresistive effect thin-film magnetic head, the MR head is better than the MR head composed of a single MR element.
A thin film called a yoke type MR head (hereinafter referred to as a YMR head) in which a magnetic flux introducing path (yoke) for guiding the magnetic flux generated from the magnetic recording medium from the head tip to the MR element part is arranged by separating the element from the head tip. It is known that the magnetic head is advantageous for improving the signal resolution and the durability of the MR element.

FIG. 3 is a perspective view of a conventional yoke type MR head. Further, FIG. 4 shows a sectional view of the structure. The upper yokes 2 and 3 are usually made of a permalloy film having a thickness of about 0.5 to 1.0 μm, and serve as a magnetic path for guiding the magnetic field generated in the magnetic recording medium 5 to the MR element 1. The MR element 1 is made of a permalloy vapor deposition film, and the film thickness is set to about 300Å and the stripe width is set to 10 to 20 μm.
Further, in order to apply a bias magnetic field to the MR element 1, Al-
A conductor 7 made of Cu is provided. The head gap 6 is 0.3 to 0.7 μ depending on the recording wavelength actually used.
It is set to about m. The lower yoke 4 is made of a high-permeability magnetic material, and a polycrystalline NiZn ferrite substrate, a single crystal or polycrystalline MnZn ferrite substrate, or a sendust thin film is used.

Conventionally, high reproduction output, upper yoke and MR
From the viewpoint of the electric insulation of the elements, the arrangement of the upper yokes 2 and 3 and the MR element 1 is such that the overlap amount ly in the plane direction is ly.
₁ , ly ₂ is ₁ to ₂ μm, the interval ovh _{1 in the} direction perpendicular to the film surface
(8) and ovh ₂ (9) were set to 0.3 μm.

[0008]

In the conventional YMR head structure, in the magnetization process of each part of the YMR head (yoke part, MR element part, etc.) in the above-described reproducing process, noise due to magnetization switching due to magnetization rotation, domain wall. Barkhausen noise generated due to movement occurs,
Noise may occur in the head playback output.

In particular, when the recording wavelength is long and the magnetic field generated from the tape is large like an analog compact cassette tape, the above-mentioned noise is likely to occur. Further, minute noise included in the reproduction output, which does not pose a problem in data restoration in reproduction of a digital signal, becomes noise in the sense of reproduction because the reproduction signal becomes a sound as it is.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a YMR head having a structure for suppressing noise such as Barkhausen noise.

[0011]

In order to solve the above problems, the structure of the thin film magnetic head according to claims 1 and 2 has a magnetoresistive effect element for detecting a signal magnetic field introduced from a magnetic recording medium, and a magnetic recording. In a yoke type magnetoresistive thin film magnetic head including a magnetic yoke for guiding a magnetic flux generated from a medium to the magnetoresistive effect element, a magnetic film is formed in a magnetic coupling portion between the magnetoresistive effect element and the magnetic yoke. The magnetoresistive effect element and the magnetic yoke do not overlap each other in the direction perpendicular to the film surface, and the gap length between the magnetoresistive effect element and the magnetic yoke is 0.01 μm.
m or more, and preferably in the range of 0.01 μm to 1.5 μm.

Next, in the structure of the thin film magnetic head according to claims 3 and 4, a magnetoresistive effect element for detecting a signal magnetic field guided from the magnetic recording medium, and a magnetic flux generated from the magnetic recording medium are applied to the magnetoresistive effect element. In a yoke type magnetoresistive thin film magnetic head having a magnetic yoke for guiding to
In the magnetic coupling portion between the magnetoresistive effect element and the magnetic yoke, the magnetoresistive effect element and the magnetic yoke overlap each other in the direction perpendicular to the film surface of the magnetic film, and the magnetism of the magnetoresistive effect element and the magnetic yoke is increased. The gap length of the film in the direction perpendicular to the film surface is 0.5 μm or more, and preferably 0.
It is characterized in that it is in the range of 5 μm to 2.0 μm.

[0013]

According to the present invention, in the yoke type magnetoresistive effect type thin film magnetic head, the magnetoresistive effect can be obtained by appropriately setting the gap length in the magnetic coupling portion between the magnetoresistive effect element and the magnetic yoke. The effect element and the magnetic yoke can be stably operated, and generation of noise such as Barkhausen noise in the reproduction output can be suppressed.

[0014]

EXAMPLES First, a method of measuring noise such as Barkhausen noise in YMR head output will be described. A measuring device for checking the presence or absence of noise such as Barkhausen noise in the MR output and the magnetic tape reproduction output with respect to the uniform external excitation magnetic field is shown in FIGS. 5 and 6, respectively (the magnetic head is shown without the magnetic yoke and the like). ) Is used to describe below.

In FIG. 5, an AC exciting current Ic is made to flow through an air-core coil 11 by a transmitter 12 and a constant current amplifier 13, and a uniform external magnetic field 15 is applied to the head 20 in the normal direction to its tape sliding surface. The head 20 is excited. This coil current value is converted into a voltage by the resistor 14 and input to the X axis of the oscilloscope 21. A constant current source 16 supplies a sense current Is to a magnetoresistive effect element 1 (hereinafter referred to as an MR element) in the head. The head output is amplified by the amplifier 17 and input to the Y axis of the oscilloscope 21. The oscilloscope is X
In the Y display mode, the head output characteristic curve (hereinafter referred to as MR
(Referred to as characteristic curve). Further, a DC bias current Ib is made to flow from the variable constant current source 19 to the bias conductor 7 in the head so that the MR characteristic curve becomes the optimum operating point. The output of the amplifier is a signal Y ′ obtained by passing noise through the fundamental wave removing circuit 18 of the differentiating circuit AC exciting current Ic and extracting the noise from the oscilloscope 2.
Input to the Y axis of 1 and measure the presence or absence of noise.

In FIG. 6, the head is attached to a tape running device (not shown in FIG. 5) and the sine wave recorded tape 23 is reproduced. A constant current source 16 supplies a sense current Is to the MR element 1 in the head. The head reproduction output is amplified by the amplifier 17 and input to CH1 of the oscilloscope 21 to observe the reproduction waveform. Further, a DC bias current Ib is made to flow from the variable constant current source 19 to the bias conductor 7 in the head and MR
Use the characteristic curve as the optimum operating point. The amplifier output is input to the distortion rate meter 22 to remove the fundamental wave and extract the noise, and the signal Y'is input to CH2 of the oscilloscope 21, and the reproduced waveform and the noise extraction waveform are simultaneously observed to measure the presence or absence of noise. .

Next, a first embodiment of the structure of the thin film magnetic head according to the present invention will be described with reference to FIG. 1 and Table 1.

[0018]

[Table 1]

FIG. 1 is a sectional view of the YMR head of the first embodiment in a direction perpendicular to the track width direction. The magnetoresistive effect element 1 and the upper yokes 2 and 3 are arranged at intervals of 1 μm in the film surface direction of the magnetic film and 0.3 μm in the film thickness direction as shown in FIG.

A prototype YM having the structure shown in the first embodiment.
For the R heads (NO. 1 and NO. 2), the results of measuring the presence or absence of noise with the above-described noise measuring device are shown in Table 1.
Shown in. In addition, for comparison, NO. 1, NO. A prototype of a conventional head structure on the same wafer as the 2nd head Y
The same measurement results are also shown in the same table for the MR heads (NO.3 to NO.5).

NO. 1, NO. With the head No. 2, no noise is generated in the uniform external excitation magnetic field MR output and the magnetic tape reproduction output. On the other hand, NO. 3 to NO. In the head of No. 5, noise is generated in both the uniform external excitation magnetic field MR output and the magnetic tape reproduction output. From this result, the upper yoke and M
It can be seen that noise is obviously suppressed in the head of the first embodiment in which the gap length with the R element is 1.0 μm.

Although the MR element is arranged below the upper yoke in the above embodiment, the MR element and the upper yoke are flush with the upper yoke so that the gap length between them is 0.01 μm or more. Noise can be suppressed even when it is arranged inside or above the upper yoke.

The larger the gap length between the MR element and the upper yoke, the greater the noise reduction effect, but the reproduction output decreases. Therefore, the gap length between the MR element and the upper yoke is preferably 0.01 μm to 1.5 μm.
The range is.

Next, a second embodiment of the structure of the thin film magnetic head according to the present invention will be described with reference to FIG. 2 and Table 2.

[0025]

[Table 2]

FIG. 2 is a sectional view of the YMR head of the second embodiment in a direction perpendicular to the track width direction. The magnetoresistive effect element 1 and the upper yokes 2 and 3 are arranged as shown in FIG. 2 with an overlap of 1.5 μm in the film surface direction of the magnetic film and an interval of 1.0 μm in the film thickness direction.

A prototype YM having the structure shown in the second embodiment.
For the R heads (NO. 6 to NO. 8), the results of measuring the presence or absence of noise with the above-described noise measuring device are shown in Table 2.
Shown in. For comparison, NO6. ~ NO. Prototype Y with the conventional head structure on the same wafer as the 8th head
The same measurement results are also shown in the same table for the MR heads (NO. 9 to NO. 11).

From these results, it can be seen that noise is suppressed in the heads (NO. 6 to 8) according to the second embodiment, in which the gap length between the upper yoke and the MR element is 1.0 μm.

Although the MR element is arranged below the upper yoke in the above-mentioned embodiment, the MR element is arranged so that the gap length between the MR element and the upper yoke is 0.5 μm or more. Noise can be suppressed even in the case of being arranged above.

The larger the gap length between the MR element and the upper yoke, the greater the noise reduction effect, but the reproduction output decreases. Therefore, the gap length between the MR element and the upper yoke is preferably in the range of 0.5 μm to 2.0 μm.

[0031]

According to the present invention described above, in the yoke type magnetoresistive effect thin film magnetic head, the gap length in the magnetic coupling portion between the magnetoresistive effect element and the magnetic yoke is appropriately set, Upper yoke (front)-
The MR element-upper yoke (back) portion has an appropriate magnetic resistance to reduce the generation of noise in the upper yoke and to increase the ratio of the signal magnetic flux flowing directly from the recording medium to the MR element. It is possible to easily suppress generation of Barkhausen noise in reproduction output even when reproducing a long wavelength recording signal such as an analog compact cassette tape without changing the magnetic characteristics of the effect element and the magnetic material of the magnetic yoke. There is.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a thin film magnetic head in a first embodiment according to the present invention.

FIG. 2 is a sectional view showing the structure of a thin film magnetic head according to a second embodiment of the present invention.

FIG. 3 is an overall perspective view showing the structure of a conventional thin film magnetic head.

FIG. 4 is a sectional view showing the structure of the conventional thin film magnetic head shown in FIG.

FIG. 5 is a block diagram of a noise measuring device for MR output characteristics by a uniform external excitation magnetic field.

FIG. 6 is a block diagram of a noise measuring device for reproducing output characteristics of a magnetic tape.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 MR element, 2, 3 Upper yoke 4 Lower yoke 5 Magnetic recording medium, 6 Magnetic head gap 7 Bias conductor, 8, 9 Space | interval perpendicular to the film surface of an upper yoke and MR element, 10 MR element lead, 11 Air core Coil 12 Oscillator, 13 Constant current amplifier, 14 Resistance, 15 Uniform external magnetic field 16 Constant current source 17 Low noise amplifier 18 Differentiation / filter circuit, 19 Variable constant current source, 20 Magnetic head 21 Oscilloscope 22 Strain rate meter 23 Magnetic tape

Claims (4)

[Claims] 1. A yoke type magnetoresistive effect comprising a magnetoresistive effect element for detecting a signal magnetic field guided from a magnetic recording medium, and a magnetic yoke for guiding a magnetic flux generated from the magnetic recording medium to the magnetoresistive effect element. Type thin film magnetic head, in the magnetic coupling portion between the magnetoresistive effect element and the magnetic yoke, a structure in which the magnetoresistive effect element and the magnetic yoke do not overlap in a direction perpendicular to the film surface of the magnetic film,
A thin-film magnetic head, wherein a gap length between the magnetically coupling portion between the magnetoresistive effect element and the magnetic yoke is 0.01 μm or more. 2. The gap length between the magnetoresistive effect element and the magnetic coupling portion of the magnetic yoke is from 0.01 μm to
2. The range is 1.5 μm or more.
The thin film magnetic head described in 1. 3. A yoke type magnetoresistive effect including a magnetoresistive effect element for detecting a signal magnetic field introduced from a magnetic recording medium, and a magnetic yoke for guiding a magnetic flux generated from the magnetic recording medium to the magnetoresistive effect element. Type thin film magnetic head, the magnetoresistive effect element and the magnetic yoke overlap each other in a direction perpendicular to a film surface of a magnetic film at a magnetic coupling portion between the magnetoresistive effect element and the magnetic yoke, and the magnetoresistive effect element And a gap length in a direction perpendicular to the film surface of the magnetic film of the magnetic yoke is 0.5 μm or more. 4. The gap length in a direction perpendicular to the film surface of the magnetic film of the magnetoresistive effect element and the magnetic yoke is 0.5.
4. The thin film magnetic head according to claim 3, wherein the thickness is in the range of .mu.m to 2.0 .mu.m.