JPS6157013A - Magnetoresistance effect type magnetic head device - Google Patents

Abstract

PURPOSE:To permit the common use of a part of a circuit in a two-channel MR type magnetic head device by obtaining first and second signal outputs corresponding to first and second signal magnetic fields from first and second low pass filters respectively. CONSTITUTION:The synthesized output of each output from first and second MR magnetosensitive parts 51 and 52 is supplied via a common capacitor 16 to a high pass filter 19 which passes a frequency component, and the output Y is supplied to first and second multipliers 231 and 232 to be multiplied with a sine wave X1 and cosine wave X2 respectively. The first and second signal outputs corresponding to he first and second signal magnetic fields HS1 and HS2 provided to the first and second MR magnetosensitive parts 5 are given at first and second output terminals 151 and 152 by supplying those multiplied outputs X1, Y, X2, and Y to the first and second low pass filters 211 and 212. This permits the common use of a circuit of the signal fetching circuit of the two-channel MR type magnetic head device.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetoresistive magnetic head device.

[Conventional technology].

First, with reference to Figure 3, we will explain the conventional boron resistance effect (hereinafter M
To explain an example of the structure of the head portion of a type magnetic head device (referred to as R), for example, Ni, Zn-based ferrite, M
On an abrasive substrate (1) made of n-Zn ferrite or the like (if this base electrode (1) has conductivity, an insulating layer (2) such as 5j02 etc. deposited thereon) is applied. In order to apply a bias magnetic field to the MR magnetic sensing part (5), which will be described later, a bias conductor (3) made of a strip-shaped conductive film that serves as a current path for generating a large magnetic field is deposited. Bias guide 4! ! For example, Ni -1? An MR magnetic sensing part (5) made of an MR magnetic thin film such as an e-based alloy or a Ni-Co-based alloy is arranged.

A thin insulating layer (6) is then formed on this M-do magnetic sensitive part (5).
For example, M as a magnetic core, each end of which extends in a direction across the bias conductor (3) and the MR magnetic sensing part (5), forming a part of the magnetic circuit, respectively.

A pair of magnetic layers (7) and (8) of permalloy is deposited. A non-magnetic insulating protective layer (9) is formed on the substrate (1).
), the protective substrate α [is bonded to the protective substrate α].

Therefore, a non-magnetic gap spacer layer (11) made of, for example, an insulating layer (6) and having a required thickness is interposed between one of the magnetic layers (7) and the front end of the substrate +11.
A front magnetic gap g is formed. Then, the front surfaces of the substrate (1), the gap spacer layer (11), the magnetic layer (7), the protective layer (9), and the protective substrate are polished by rt7F so that the magnetic gap g faces the magnetic tape. A surface <12) facing the magnetic recording medium is formed.

Further, the rear end of the magnetic layer (7) constituting the magnetic gap g and the front end of the other magnetic layer (8) are connected to the MR magnetic sensing portion (
5) A discontinuous portion (13) is formed between both ends of the discontinuous portion (13), which is formed so as to straddle the insulating layer (6). The rear end and the front end of both magnetic layers (7) and (8), respectively, are electrically separated by the interposition of the insulating layer (6);
Although they are insulated, they are magnetically coupled at the discontinuous portion (13). Hidden, base IJi
(n - magnetic gap g - magnetic layer + 71 - M R magnetic sensing part (5) - magnetic layer (8) A magnetic circuit consisting of a closed magnetic path of one substrate (1) is formed.

In such an MR type magnetic head section, the signal magnetic flux from the front gap g that is in contact with the magnetic recording medium flows through the above-mentioned magnetic circuit, thereby increasing the resistance of the MR magnetic sensing section (5) in this magnetic circuit. The value changes according to the external magnetic field caused by this signal magnetic flux.

Therefore, a detection current is passed through the MR magnetic sensing section (5), and this change in resistance value is detected as a voltage change across the MR magnetic sensing section (5), thereby reproducing the recorded signal on the magnetic medium.

In this case, in order for the MR magnetic sensing section (5) to operate linearly as a magnetic sensor and to have high sensitivity, it is necessary to magnetically bias the MR magnetic sensing section (5).

This Pias magnetic field is a DC magnetic field given by a magnetic field generated by energizing the bias conductor (3) and a magnetic field itself generated by the detection current flowing to the MR magnetic sensing part (5).

That is, this type of MR type (d-type head device, whose schematic configuration is not shown in FIG. In a state where a bias magnetic field He is applied by the generated magnetic field and the magnetic field generated by energizing the detection current inn to the MR magnetic sensing part (5), the signal magnetic field H from the magnetic medium described above is applied.
3 is passed. Based on the resistance change caused by this signal magnetic field H8, the voltage across the MR magnetic sensing section (5), that is, A
The change in potential at the point is supplied to the amplifier (14) via the low-frequency IF capacitor (161), amplified, and output to the output terminal (161).
5).

FIG. 5 shows an operating characteristic curve diagram showing the relationship between the magnetic field H applied to this MR magnetic sensing part (51) and its resistance value R, and this supplementary line indicates the range -HBR~ where the absolute value of the magnetic field H is small. 10HB
H shows an upwardly convex quadratic curve, but when the absolute value of the magnetic field H becomes large and deviates from this range, the MR magnetic sensing part (
5) The magnetization in the central part of the MR magnetic thin film that constitutes
approaches the minimum value Ra1n. Incidentally, the maximum resistance R (+I￥ Rmax is the value in the state where all the magnets 4B of the MR magnetic strips are oriented in the current direction. Then °ζ,
In the characteristic part of the quadratic curve in this operating characteristic curve, while the bias magnetic field HR described above is applied, the signal magnetic field from the magnetic medium indicated by the symbol (17) in Figure @5 is applied. , Accordingly, the symbol ゛ζ in the same figure (
The output is obtained based on the change in resistance value shown in 1 day). In this □ case, it can be seen that the larger the magnitude of the signal magnetic field is, the larger the second harmonic □ wave distortion becomes.

Furthermore, the potential at point A in FIG. 4 in the above-mentioned MR type magnetic head device is determined by the combination of the fixed resistance and the variable resistance of the MR magnetic sensing part (5). The resistance is as high as about 98%, and since the temperature dependence of the fixed resistance is large, there is a drawback that the temperature drift of the potential at point A is large. This MR magnetic sensing part (
The resistance value R of 5) is R=Ro(1・+αcos2θ) (where, Ro is the fixed resistance, α is the maximum resistance change rate, θ
is the angle between the current direction and the grinding direction in the MR magnetic sensing part (5). For example, if the MR magnetic sensing part (5) is
Thickness 2 due to 1N+ -19Fe (permalloy) alloy
The actual value of α in the case of 50 MR magnetic thinners is α−
It is about 0,017. The value of α is the MR magnetic sensing part (5
Although there are some differences depending on the film thickness and material of the MR magnetic thin film of ), it is approximately α-0.05 at most.

On the other hand, the fixed bone Ro of this resistance is given by Ro=Ri(1+aΔt) (where Ri is the initial value of resistance, a is the temperature coefficient, and Δt is the temperature change), and the above-mentioned MR magnetic sensing part ( 5
) The actual measured value of the temperature coefficient a in the example is a = 0.0
It is about 027/deg. This results in large noise in detecting a DC magnetic field.

Furthermore, in the case of this type of MR type magnetic head unit, since its temperature coefficient is large as mentioned above, the temperature coefficient is generated by, for example, energization to the MR magnetic sensing part (5) or bias current to the bias conductor (3). If this heat is radiated unstably due to the head's sliding contact with the magnetic recording medium and the temperature of the head changes, a large red noise, so-called sliding noise, will be generated.

Furthermore, when the amplifier (14) in the configuration shown in FIG. The capacitance C required for (16) is C=−Rω0 (ωo=2πfo), where R is the resistance of the MR magnetic sensing part (5). Now, if the MR magnetic sensing part (5) is made of the above-mentioned permalloy with a thickness of 250 mm and its length is 50 μm, its resistance R will be about 1000, so if f o =1 kllz, then the capacitor (
16) requires a large value of C=t and aμF, which is particularly problematic when constructing a multi-track type magnetic head device for digital audio signals.

In addition, it is desirable that the magnetic permeability in the magnetic circuit, especially in the magnetic layers (7) and (8) which are relatively thin and have a small cross-sectional area, be as high as possible. Therefore, applying a bias magnetic field as described above will result in a decrease in magnetic permeability.

The above-mentioned DC bias type MR type magnetic head device has the advantage of having a wide effective track width and easy to change to a fall track, but on the other hand, it has poor linearity, difficulty in DC reproduction, and large sliding noise. The drawback is that the noise is large and the output varies widely.

Other conventional MR magnetic head devices that have been proposed include a differential MR magnetic head device and a Barberball MR magnetic head device. A differential MR type magnetic head device is provided with a pair of MR magnetic sensing parts in its MR type magnetic throat part, and a common bias conductor applies opposite bias magnetic fields to the pair of MR magnetic sensing parts. and a pair of M
Applying the same signal magnetic field to the R magnetic sensing parts so that a differential output corresponding to the signal magnetic field can be obtained from the pair of MR magnetic sensing parts,
The differential output is supplied to a differential amplifier, and a reproduced signal is obtained from the differential amplifier.

This differential MR type magnetic head device is capable of direct current reproduction (
However, although it has the advantages of low Barkhausen noise, removal of second-order harmonic distortion, low output fluctuation, and only a differential amplifier is required as a circuit, The disadvantages are that the mitigation effect is small, the effective track width is narrow, and it is difficult to convert to autumn tracks.

In addition, the Barberpole 2 MR magnetic head device has its MR
A large number of mutually parallel conductor bars made of gold or the like are adhered to the MR sensing part of the magnetic head part so as to be oblique to the longitudinal direction of the MR sensing part.

This barber pole type MR type magnetic gutter device has less Barkhausen noise and less variation in output.
Although it has the advantage of requiring only an amplifier as a circuit,
The drawbacks are that DC reproduction is difficult, sliding noise is large, narrowing the track is difficult, and the effective track width is not very wide.

Therefore, in order to eliminate or improve the above-mentioned drawbacks,
Previously, the present applicant filed an application for a new magnetoresistive magnetic head device in Japanese Patent Application No. 1983-38980.

An example of the previously proposed MR type magnetic head device will be described below with reference to FIG. In this example, the MR
The magnetic head section has the same structure as that explained in FIGS. 3 and 4, and in FIG. 6, the same reference numerals are given to the parts corresponding to those in FIGS. Omitted. In this example, an alternating current bias current i^ with a high frequency fc (frequency more than three times the maximum frequency of the signal magnetic field) is caused to flow through the bias conductor (3) of the MR type magnetic head.
An alternating current magnetic field is applied to the MR magnetic sensing section (5). Here, the waveform of the AC bias current iA, and thus the waveform of the AC magnetic field, may be a sine wave, a rectangular wave, or any other waveform.

Then, the output of the MR magnetic sensing part (5) is connected to a capacitor (16).
is supplied to a high-pass filter (I9) that passes the component of frequency fc through a multiplier vl.
(22) and multiplied by an AC signal X having the same phase and frequency as the AC bias magnetic field described above. By supplying the multiplication output XY to the low-pass filter (21), a signal output corresponding to the signal magnetic field Its applied to the MR magnetic sensing section (5) can be obtained at the output terminal (15).

According to the previously proposed MR type magnetic head device, it is possible to obtain output with excellent linearity and low distortion, DC reproduction is possible, temperature drift is small, sliding noise is improved, and the effective trunk width is It has the advantage of being large, narrowing the track, reducing the capacitance of the capacitor, and increasing the dynamic range.
In addition, in this case, it is possible to avoid a decrease in the magnetic permeability of the magnetic circuit.

[Problem that the invention seeks to solve]

By the way, when the MR type magnetic head device proposed earlier in FIG. 6 is made to have multiple channels, a number of circuits corresponding to the number of channels are required.

In view of this point, the present invention provides an MR type magnetic head device that can share a part of the circuit of a two-channel MR type magnetic head device.
This is an attempt to propose a type of magnetic head device.

[Means for solving problems]

The MR type magnetic head device according to the present invention includes first and second magnetoresistive effect magnetic sensing parts (MR magnetic sensing parts) (5z) to which first and second signal magnetic fields HSL and Hs2 are respectively applied.
, (52) and the first and second MR magnetic sensing parts (51
), (52) to apply first and second alternating current bias magnetic fields having the same frequency and a phase difference of 90'' from each other.
and second bias magnetic field generating means (24A) (or (2
4B)), (31), (32) and corresponding to the first and second signal magnetic fields Hsi and HS'2 from the respective outputs of the first and second MR magnetic sensing parts (5r) and (52). Signal extraction means (22) for extracting a composite signal of signal outputs
and first and second AC signals synchronized with the first and second AC bias magnetic fields and the composite signal.
Multiplication means (231).

(232) and the first and second multiplication means (23i
).

(212), to which respective outputs of (232) are supplied, the first and second low pass filters (2h).

(212), the first and second signal magnetic fields Hst, Hs
In this embodiment, first and second signal outputs corresponding to 2 are obtained.

[Effect]

According to the present invention, the first and second MR magnetic sensing parts (5
1) and (52), a common signal extraction means (22) extracts a composite signal of the signal outputs corresponding to the first and second signal magnetic fields, and this composite signal is used as the Multiplication means (23+).

(232) and the first and second MR magnetic sensing parts (5
1), (52)・, the same frequency is given to Saini 9
First and second alternating current bias magnetic fields having a phase difference of 0° are multiplied by first and second alternating current signals synchronized with each other, and the respective multiplication outputs are passed through first and second low-pass filters (21z).
, (212), the first and second low pass filters (211).

(212), the first and second MR magnetic sensing parts (51)
.

(52) The first and second signal magnetic fields H31,
First and second signal outputs corresponding to H32 can be obtained separately.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. hx and h2 are first and second head parts, respectively, and first and second bias conductors (3z), respectively.

(32) and first and second MR magnetic sensing parts (51).

(52), and its structure is the same as that shown in FIG. A detected DC current i MR is passed through the first and second MR magnetic sensing parts (5z) and (52) which are connected in parallel (serial connection is also possible). Sine wave/cosine wave oscillator (24
A) Sine wave and cosine wave signals X of the same frequency fc from
i and X2 are buffer circuits (251).

(252), from which sine wave and cosine wave bias currents are respectively supplied to the bias conductor (31).

(32). First and second MR magnetic sensing parts (51
), (52) includes the first and second signal magnetic fields H81,
Hs2 is given separately.

(16) and (19) are a capacitor and a high-pass filter, respectively, which constitute the signal extraction means (22).

1 of the first and second MR magnetic sensing parts (51) and (52)
1 The combined output of each output is connected to a capacitor (
16) in common to a frequency band pass filter (19) that passes the frequency fc component, and its output Y is supplied to the first
and second multipliers (231) and (232) to be multiplied by the sine wave and cosine wave signals X1 and X2, respectively.

By supplying the multiplication outputs XIY, X2Y to the first and second low-pass filters (211) and (212), the first and second output terminals (151) are connected.

At (152), first and second signal outputs corresponding to the first and second signal magnetic fields H31 and H82 applied to the first and second MR magnetic sensing sections (5) are obtained.

Next, the operation of the embodiment shown in FIG. 1 will be analyzed using mathematical formulas.

First, the maximum resistance of the MR magnetic sensing part is Rn, the maximum resistance change rate is afi, the anisotropic magnetic field is Hkn, and the amplitude of the bias magnetic field is I(
BOTI, signal magnetic field HSn (t), MR magnetic sensing part (5
1), (52) as t1+i2 (i
t = i2). Further, the relationship between the magnetic field H and the resistance rn characteristic curve in FIG. 5 is as shown in the following equation.

Furthermore, the bias magnetic fields HBt and MR2 generated by the MR magnetic sensing parts (51) and (52) are expressed as follows.

HB1=HBo1sin (wt) −
・-+21HB2=HBO2C(1!l (i*t)
, --(31MR magnetic sensing part (51)+,
Hsn(tl (Hsz(t),
It is assumed that the frequency spectrum of Hs2 (11) has only the maximum signal frequency fs or less, and the bias frequency fc is selected to satisfy fc>3fs. The output VMRn of the MR magnetic sensing section at this time is expressed by the following equation.

VMRn = tn x rTl (4) If only the variation in the output of the MR magnetic sensing section is evaluated, the following equation is obtained.

Here, by substituting equation (2) for Hn, the following equation is obtained.

(6) Now, the output variation VA when the MR magnetic sensing sections (51) and (52) are connected in series is expressed as follows.

VA = VtlRt + vtlR2 Then, equation (7) can be expressed as the following equation.

VA = 1 (,, HBt+j(st(tl)2+
2 (HB2+Hs2(t))2−=(81this(
By substituting equations (21 and (31) into equation (8), equation (8) can be expressed as the following equation.

VA = 1 (Hsot sin (wt) +
Hs1(tl) ”+K (HBO2cos (wt
) +Hs2Tt)) 2=Kx (HBOt s
in 2(wt) +211e6x Hsl(tl
sin (wt)+ (HsITt)) 2)
+2 (HB02cos 2(wt)+2HB
O2Hst(t) cos (wt) + (H
st(tl) 2) (9) This voltage VA is amplified by an amplifier (with an amplification factor of A). Now, considering the case where this VA is multiplied by sin(wt) by the multiplier (23z), the multiplication output z1 is expressed as in the following equation.

zl ;A-v^ Risin wt =AKz (Hlloz sin3(wt) +2
+Iaot Hst(tlsin2(wt) + (H
st (tl) 2 sin (wt) ) + 4 to 2
(H?r62 cos2(wt) sin (
wt)+2HBO2Hst(t) cos (wt)
sin (wt) + '(Hst(t)) 2sin
(wt) ) −−0[eIf this output z1 is passed through a low-pass filter (2h) to cut off the ω component or higher, the term sin” (wt)→0 the term sin2(Wt)→2 the term sin gat →0 cos2(gat) sin wt term is (1-5in2
(Kat)) sin wt = sin wt-si
n” (wt) →02cos (wt) sin
(wt) = 2sin (2wt) → 0, and as a result, the output v1 of the filter (2h) is expressed as the following equation.

V+=AKt・Hso+・HsITt1−・・・−−(
11) Similarly, the output v2 of the filter (212) is also expressed as in the following equation.

V2 = AK2 ・HBOt・Hst(11--(1
2) Next, another embodiment of the present invention will be described with reference to FIG. 2, but parts corresponding to those in FIG. In this example, the sine wave shown in FIG.
In place of the cosine wave oscillator (24A), a rectangular wave oscillator (24B) is provided which generates first and second rectangular wave signals having the same frequency and a phase difference of 90° from each other. The signal extraction means (22) is composed of a capacitor (16) and an amplifier (14). Also, first and second multipliers (23t),
・(232) is an inverter (26) and an amplifier (14)
) consists of first and second changeover switches (271) and (272) that control switching of the inverted and non-inverted outputs of the inverted and non-inverted outputs using first and second rectangular wave signals having a phase difference of 90'' from each other. do.

First and second changeover switches (27z), (2
72) are passed through first and second low-pass filters (2
11).

(212).

The embodiment shown in FIG. 2 has the same advantages as the differential MR type magnetic bed device, such as being able to remove second-order harmonic distortion, and also has the advantage of having a wide effective track width and making narrow tracks possible. It has advantages that dynamic MR type magnetic head devices do not have.

Digital/analog audio/video signals are possible as playback signals =□ [Effects of the Invention] According to the present invention described above, part of the circuit of a two-channel MR type magnetic head device, that is, the signal extraction circuit An MR type magnetic head device that can be shared can be obtained.

[Brief explanation of drawings]

1 and 2 are small lock diagrams showing each embodiment of the magnetoresistive magnetic head device according to the present invention, and FIG. 3 is a diagram showing the structure of the head section of a conventional magnetoresistive magnetic head device. 4 is a block diagram showing a conventional magnetoresistive magnetic head device. FIG. 5 is a characteristic curve diagram showing the magnetic field-resistance characteristics of the magnetoresistive part. FIG. 2 is a circuit diagram showing a magnetoresistive magnetic head device proposed in 2003. (3'z), (3'2) are the first and second bias conductors, (51), '' (52) are the first and second magnetoresistive magnetic sensing parts, (2b)', ( 212)
are the first and second low-pass filters, (22) is the signal extraction means, (231) and (232) are the first and second low-pass filters;
is a multiplier. Procedural amendment December 10, 1988 Patent Application No. 178833 2 Title of invention Magnetoresistive magnetic head device 3 Relationship with the person making the amendment Case Patent applicant address Tokyo Parts District Kitashinyo 6-7-35 Name (2
18) Sony Corporation Representative Director Norio Ohga 4, Agent Address: 1-8-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo 03-
343-5821&t'l (Shinjuku Building) 6, number of inventions increased by amendment 8, content of amendment il+ In the specification, page 11, lines 18 to 19 and 1
Page 6, lines 1 and 2 [Frequency...Filter (1) J is corrected to [Amplifier (14) J]. +2) Same, page 16, line 1-line r(19) is corrected to read ``r(14)''. (3) Same page, line 18, “High-pass filter” is replaced with “
"Amplifier", corrected. (4) In the drawings, Figures 1 and 6 will be corrected as shown in the attached sheet. that's all

Claims (1)

[Claims] First and second magnetoresistive magnetic sensing parts to which the first and second signal magnetic fields are applied separately, and the first and second magnetoresistive magnetic sensing parts have the same frequency and a phase difference of 90° from each other. first and second bias magnetic field generating means for providing first and second alternating current bias magnetic fields having a signal extraction means for extracting a composite signal of signal outputs corresponding to the magnetic field; and a first signal extracting means for multiplying the composite signal by first and second AC signals synchronized with the first and second AC bias magnetic fields.
and a second multiplication means, and first and second low-pass filters to which respective outputs of the first and second multiplication means are supplied, the first and second low-pass filters. From the above 1st
and a magnetoresistive magnetic head device, characterized in that first and second signal outputs corresponding to the second signal magnetic field are obtained.