JPH0532805B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetoresistive magnetic head device.

[Conventional technology]

First, referring to FIG. 3, an example of the structure of the head section h of a conventional magnetoresistive (hereinafter referred to as MR) type magnetic head device will be described. For example, Ni-Zn ferrite, Mn-Zn ferrite, etc. (If this substrate 1 has conductivity, an insulating layer 2 such as SiO ₂ deposited thereon)
A bias conductor 3 made of a strip-shaped conductive film is deposited on the bias conductor 3 to serve as a current path for generating a bias magnetic field to apply a bias magnetic field to the MR magnetic sensing part 5, which will be described later. , for example, Ni-Fe alloy or Ni-
MR magnetic sensing part 5 made of MR magnetic thin film such as Co-based alloy
will be arranged. A magnetic conductor is placed on the MR magnetic sensing part 5, with one end of each extending across the bias conductor 3 and the MR magnetic sensing part 5 through a thin insulating layer 6, and forming a part of the magnetic circuit. A pair of magnetic layers 7 and 8, for example made of Mo permalloy, as a core.
is deposited. A protective substrate 10 is bonded onto the substrate 1 with a nonmagnetic insulating protective layer 9 interposed therebetween.

Thus, a non-magnetic gap spacer layer 11 made of, for example, an insulating layer 6 and having a required thickness is interposed between one magnetic layer 7 and the front end of the substrate 1 to form a front magnetic gap g. Ru. Then, the substrate 1,
The front surfaces of the gap spacer layer 11, the magnetic layer 7, the protective layer 9, and the protective substrate 10 are polished to form a surface 12 that faces a magnetic recording medium such as a magnetic tape.

Furthermore, although the rear end of the magnetic layer 7 and the front end of the other magnetic layer 8 constituting the magnetic gap g are formed so as to straddle the MR magnetic sensing part 5 via the insulating layer 6, both ends are Discontinuous portions 13 spaced apart from each other are formed therebetween. The rear and front ends of both magnetic layers 7 and 8 are electrically insulated by the presence of the insulating layer 6, but are magnetically coupled at the discontinuous portion 13. Thus, the substrate 1 - magnetic gap g - magnetic layer 7 - MR magnetic sensing part 5 - magnetic layer 8
- a magnetic circuit consisting of a closed magnetic path of the substrate 1 is formed;

In such an MR type magnetic head section h,
When 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, the resistance value of the MR magnetic sensing part 5 in this magnetic circuit is
It changes depending on the external magnetic field caused by this signal magnetic flux.
Therefore, a detection current is applied to 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 have high sensitivity, this
It is necessary to magnetically bias the MR magnetic sensing section 5. This bias magnetic field is a DC magnetic field provided 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 section 5.

That is, this type of MR type magnetic head device has a fourth
As shown in the figure, the MR magnetic sensing section 5
, the magnetic field generated by the application of DC current i _B to the bias conductor 3 and the detection current i _MR to the MR magnetic sensing part 5
The signal magnetic field H _S from the magnetic medium described above is applied while the bias magnetic field H _B is applied by the magnetic field generated by the energization of the magnetic medium. Then, the MR magnetic sensing part 5 based on the resistance change due to this signal magnetic field H _S
, that is, the change in the potential at point A, is supplied to the amplifier 14 via the low-frequency blocking capacitor 16, where it is amplified and output from the output terminal 15.

FIG. 5 shows the magnetic field H applied to this MR magnetic sensing part 5.
This curve shows an upwardly convex quadratic curve in the range -H _BR to +H _BR where the absolute value of the magnetic field H is small. When the absolute value of becomes large and deviates from this range, the magnetization of the central part of the MR magnetic thin film constituting the MR magnetosensitive section 5 begins to saturate in the direction of the magnetic circuit, departing from the quadratic curve, and its resistance R becomes Minimum value R _nio
Asymptotes to . Incidentally, the maximum value R _nax of this resistance R
is the value when all the magnetization of the MR magnetic thin film is oriented in the current direction. Then, in the characteristic portion of the quadratic curve in this operating characteristic curve, the signal magnetic field from the magnetic medium shown with reference numeral 17 in FIG. 5 is applied while the bias magnetic field H _B described above is applied. Accordingly, an output based on the change in resistance value indicated by number 18 in the figure is obtained. In this case, it can be seen that as the magnitude of the signal magnetic field increases, the second harmonic distortion increases.

Moreover, the fourth magnetic head in the above-mentioned MR type magnetic head device
The potential at point A in the figure is a potential determined by the combination of the fixed resistance and the variable resistance of the MR magnetic sensing section 5.
In this case, the fixed portion is about 98%, and the temperature dependence of the fixed portion of this resistance is large, so there is a drawback that the temperature drift of the potential at point A is large. The resistance value R of this MR magnetic sensing part 5
R = Ro (1 + α cos ² θ) ... (1) (where, Ro is the fixed resistance, α is the maximum resistance change rate, and θ is the angle between the current direction and the magnetization direction in the MR magnetic sensing part 5. ), for example MR
When the magnetically sensitive part 5 is made of an MR magnetic thin film of 81Ni-19Fe (permalloy) alloy with a thickness of 250 Å, the actual value of α is approximately 0.017. The value of this α is MR
Although there are some differences depending on the thickness and material of the MR magnetic thin film of the magnetosensitive section 5, α=0.05 at most.
On the other hand, the fixed portion Ro of this resistance is Ro=Ri(1+aΔt)...(2) (However, Ri is the initial value of the resistance, a is the temperature coefficient,
Δt is the temperature change), and the above MR
The actual measured value of the temperature coefficient a in the example of the magnetically sensitive part 5 is a
= about 0.0027/deg. This results in large noise in detecting a DC magnetic field.

Furthermore, in the case of this type of MR type magnetic head section, since its temperature coefficient is large as described above, heat generated by, for example, energization to the MR magnetic sensing section 5 or bias current to the bias conductor 3, etc. However, if the temperature of the head changes due to unstable heat dissipation due to the sliding contact between the head and the magnetic recording medium,
A large noise, so-called sliding noise, will be generated.

Furthermore, when the amplifier 14 in the configuration shown in FIG.
The required capacitance C is as follows, where R is the resistance of the MR magnetic sensing section 5: C=1/R〓 _p (3) (ωo=2πfo). Now, if the MR magnetic sensing part 5 is made of permalloy with a thickness of 250 Å as mentioned above and its length is 50 μm, its resistance R will be about 120 Ω, so if fo = 1 kHz, the capacitor 16 should be C = 1.3 μF. This is a problem especially when constructing a multi-track type magnetic head device for digital audio signals.

Furthermore, it is desired that the magnetic permeability in the magnetic circuit, particularly in the magnetic layers 7 and 8, which are relatively thin and have a small cross-sectional area, be as high as possible, and this magnetic permeability is maximum when the external magnetic field is zero. So,
Applying a bias magnetic field as described above causes 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 being easy to make into a clamping track, but has poor linearity, difficulty in DC regeneration, large sliding noise, and Barkhausen. It has the drawbacks of high noise and wide variation in output.

As other conventional MR type magnetic head devices, a differential type MR type magnetic head device, a barber pole type MR type magnetic head device, etc. have been proposed. A differential MR type magnetic head device has a pair of MR magnetic sensing parts in its MR type magnetic head part, and a pair of MR magnetic sensing parts.
A common bias conductor applies opposite bias magnetic fields to the MR magnetic sensing parts, the same signal magnetic field is applied to a pair of MR magnetic sensing parts, and a differential output corresponding to the signal magnetic field is generated from the pair of MR magnetic sensing parts. The differential output thereof 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 regeneration (however, the offset variation is large).
Although it has the advantage of having little Barkhausen noise, eliminating second-order harmonic distortion, having little variation in output, and requiring only a differential amplifier as a circuit, it has little effect in reducing sliding noise and has a limited effective track width. The disadvantage is that it is difficult to clamp and create a clamp track.

In addition, the barber pole type MR type magnetic head device has a large number of mutually parallel conductor bars made of gold etc. attached to the MR magnetic sensing part of the MR type magnetic head part so as to be diagonal in the longitudinal direction. It was formed.

This barber-pole type MR type magnetic head device has the advantage of having low Barkhausen noise, little variation in output, and requires only an amplifier as a circuit. However, it is difficult to reproduce direct current, has large sliding noise, and is difficult to use. It has the drawbacks that it is difficult to carry out and the effective track width is not very wide.

Therefore, in order to eliminate or improve the above-mentioned drawbacks, the present applicant previously filed a novel magnetoresistive magnetic head device as Japanese Patent Application No. 59-38980.

An example of the previously proposed MR type magnetic head device will be explained below with reference to FIG. In this example, the MR type magnetic head section h has the same configuration as that explained in FIGS.
In the figure, parts corresponding to those in FIGS. 3 and 4 are designated by the same reference numerals, and redundant explanation will be omitted. In this example, the bias conductor 3 of the MR type magnetic head section h
An alternating current bias current i _A of high frequency fc (frequency three times or more than the maximum frequency of the signal magnetic field) is applied to the MR magnetosensitive section 5 to apply a direct current magnetic field. Here, the waveform of the alternating bias current _iA , and thus the waveform of the alternating magnetic field, may be a sine wave, a rectangular wave, or any other waveform.

Then, the output of the MR magnetic sensing section 5 is connected to the capacitor 16.
The output Y thereof is supplied to the multiplier 22 and multiplied by the AC signal X having the same phase and frequency as the above-mentioned AC bias magnetic field. By supplying the multiplication output XY to the low-pass filter 21, a signal output corresponding to the signal magnetic field H _S applied to the MR magnetic sensing section 5 can be obtained at the output terminal 15.

According to the MR type magnetic head device proposed earlier,
It is possible to obtain output with excellent linearity and low distortion, DC regeneration is possible, and temperature drift is small.
Sliding noise is improved, effective track width is large,
It has the advantage of being able to be used as a clamping track, and furthermore, the capacitance of the capacitor can be reduced, and the dynamic range can be increased, and in some cases, it is possible to avoid a decrease in 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, the present invention provides a two-channel MR system.
The purpose of this paper is to propose an MR type magnetic head device in which a part of the circuit of the MR type magnetic head device can be shared.

[Means for solving problems]

The MR type magnetic head device according to the present invention has first and second magnetoresistive effect magnetic sensing parts (MR magnetic sensing parts) 5 ₁ and 5 to which first and second signal magnetic fields H _S1 and H _S2 are respectively applied. ₂ , and the first and second MR magnetic sensing parts 5 ₁ ,
_First and second bias magnetic field generating means 24A {or 24
B}, 3 ₁ , 3 ₂ and the first and second MR magnetic sensing parts 5 ₁ ,
5. From each output of ₂ , the first and second signal magnetic fields H _S1 ,
a signal extraction means 22 for extracting a composite signal of signal output corresponding to H _S2 ; and first and second AC signals synchronized with the first and second AC bias magnetic fields and multiplying the composite signal by the first and second AC signals; Multiplying means 23 ₁ , 2
3 ₂ and the first and second multiplication means 23 ₁ , 23
_the first and second low-pass filters 21 ₁ , 21 ₂ to which respective outputs of _{2 are} supplied; The first and second signal outputs corresponding to the signal magnetic fields H _S1 and H _S2 are obtained.

[Effect]

According to the present invention, signals corresponding to the first and second signal magnetic fields are output from the respective outputs of the first and second MR magnetic sensing sections 5 ₁ and 5 ₂ by the common signal extraction means 22. The synthesized signal is taken out, and the synthesized signal is supplied to the first and second multiplication means 23 ₁ and 23 ₂ to be applied to the first and second MR magnetic sensing sections 5 ₁ and 5 ₂ . First and second AC bias magnetic fields having a phase difference of 90 degrees are multiplied by first and second AC signals synchronized with each other, and the respective multiplication outputs are passed through first and second low-pass filters 21 ₁ , 21 ₂ , the _first and _second MR
First and second signal outputs corresponding to the first and second signal magnetic fields H _S1 and H _S2 applied to the magnetic sensing parts 5 ₁ and 5 ₂ can be obtained separately.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. h ₁ and h ₂ are first and second head parts, respectively, and have first and second bias conductors 3 ₁ and 3 ₂ and first and second MR magnetic sensing parts 5 ₁ and 5 ₂ respectively. The structure is similar to that shown in FIG. The first and second connected in parallel (serial connection is also possible)
A detected DC current i _MR is passed through the MR magnetic sensing parts 5 ₁ and 5 ₂ . Sine wave and cosine wave signals X ₁ and X ₂ of the same frequency fc from the sine wave/cosine wave oscillator 24A are supplied to buffer circuits 25 ₁ and 25 ₂ , and the sine wave and cosine wave bias currents from these are applied to the bias conductors, respectively. 3 ₁ ,
3 I was swept away by ₂ . first and second MR magnetic sensing parts 5 ₁ ,
5 ₂ are respectively provided with first and second signal magnetic fields H _S1 and H _S2 .

16 and 14 are a capacitor and an amplifier, respectively, which constitute the signal extraction means 22. first and second
The combined output of the MR magnetism sensitive sections 5 ₁ and 5 ₂ is commonly supplied to the amplifier 14 via the capacitor 16, and the output Y is sent to the first and second multipliers 23 ₁ ,
23 ₂ to provide sine wave and cosine wave signals respectively
Multiply by X ₁ and X ₂ . By supplying the multiplication outputs X ₁ Y and X ₂ Y to the first and second low-pass filters 21 ₁ and 21 ₂ , the first and second output terminals 1
At 5 ₁ and 15 ₂ , first and second signal outputs corresponding to the first and second signal magnetic fields H _S1 and H _S2 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 R _o , the maximum resistance change rate is a _o , the anisotropic magnetic field is H _ko , the amplitude of the bias magnetic field is H _BOo , the signal magnetic field is H _so (t), and the MR magnetic sensing part 5
Let the detection currents flowing through ₁ and 5 ₂ be i ₁ and i ₂ (i ₁ =i ₂ ).
Also, the relationship between the magnetic field H-resistance r _o characteristic curve in Fig. 5 is as follows:
It is as follows.

r _o = R _o {1-a _o (H/H _ko ) ² } ...(1) Also, the bias magnetic field given to the MR magnetic sensing parts 5 ₁ and 5 ₂
H _B1 and H _B2 are expressed as follows.

H _B1 = H _BO1 sin (wt) ...(2) H _B2 = H _BO2 oos (wt) ...(3) H _So (t) {H _S1 given to the MR magnetic sensing parts 5 ₁ and 5 ₂
(t), H _S2 (t)} has only the maximum signal frequency fs or less, and the bias frequency fc
, select fc>3fs. The output v _MRo of the MR magnetic sensing section at this time is expressed as follows.

v _MRo = i _o × r _o = i _o・R _o {1−a _o (H/H _ko ) ² }……(4
) If only the variation in the output of the MR magnetic sensing part is evaluated, the following equation is obtained.

v _MRo = −i _o・R _o・a _o (H _o /H _ko ) ² } ...(5) Here, by substituting equation (2) for H _o , the following equation is obtained.

v _MRo = −i _o・R _o・a _o (H _Bo + H _So (t)) ₂ /H _ko ² ...(6) Now, the output when MR magnetic sensing parts 5 ₁ and 5 ₂ are connected in series The variation v _A is expressed as follows.

v _A = v _MR1 + v _MR2 = −i ₁ R ₁ a ₁ /H ² / _k1 (H _B1 +H _S1 (t)) ²
−i ₂ R ₂ a ₂ /H ² / _k2 (H _B2 + H _S2 (t))……(7) Here, K ₁ ≡−i ₁ R ₁ a ₁ /H ² / _k1 , K ₂ ≡i _{2 R2a2 /} ^H2 / _k2
Then, equation (7) can be expressed as the following equation.

v _A = K ₁ (H _B1 + H _S1 (t)) ² + K ₂ (H _B2 + H _S2 (t)) ² ...(8) Substituting equations (2) and (3) into equation (8), we get Equation (8) is expressed as the following equation.

v _A =K ₁ {H _BO1 sin (wt) + H _S1 (t)} ² +K {H _BO2 cos (wt
) +H _S2 (t)} ² = K ₁ [H ² _BO1 sin ² (wt) + 2H _BO1 H _S1 (t)sin
(wt) + {H _S1 (t)} ² ] +K ₂ [H ² _BO2 cos ² (wt) + 2H _BO2 H _S2 (t)cos (wt) + {H
_S2 (t)} ² ]...(9) This voltage v _A is amplified by an amplifier (with an amplification factor of A). Now, if we consider the case where this v _A is multiplied by sin(wt) by the multiplier ₂₃₁ ,
The multiplication output Z ₁ is expressed as follows.

Z ₁ = A・v _A・sinwt=AK ₁ [H ² _BO1 sin ³ (wt) +2H _BO1 H _S1 (t)sin ² (wt) +{H _S1 (t)} ² sin (wt)] +AK ₂ [ H ² _BO2 cos ² (wt) sin (wt) +2H _BO2 H _S2 (t) cos (wt) sin (wt) + {H _S2 (t)} ² sin (wt)] ...(10) This output Z ₁ When passing through the low-pass filter 21 ₁ and blocking the ω component or higher, the term sin ³ (wt) → 0 sin ² (wt) term → 1/2 term sin wt → 0 cos ² (wt) term sin wt is (1-sin ² (wt)) sin wt=sin wt-sin ³ (wt)→0 2cos(wt) sin(wt)=2sin(2wt)→0, and as a result, the output V ₁ of filter ₂₁₁ is It is expressed as the following formula.

V ₁ =AK ₁ ·H _BO1 ·H _S1 (t) (11) Similarly, the output V ₂ of the filter 21 ₂ is also expressed as in the following equation.

V ₂ =AK ₂・H _BO2・H _S2 (t) ...(12) Next, another embodiment of the present invention will be explained with reference to FIG. 2, but the parts corresponding to FIG. The same reference numerals are used to omit redundant explanation. In this example,
Instead of the sine wave/cosine wave oscillator 24A in Fig. 1,
A square wave oscillator 24 that generates first and second square wave signals having the same frequency and a phase difference of 90 degrees from each other.
Provide B. The signal extraction means 22 is connected to the capacitor 16.
and an amplifier 14. Also, the first and second
The multipliers 23 ₁ and 23 ₂ switch and control the inverter 26 and the inverting and non-inverting outputs of the amplifier 14 using first and second rectangular wave signals having a phase difference of 90° from each other. and second changeover switch 2
Consists of 7 ₁ and 27 ₂ . The respective outputs of the first and second changeover switches 27 ₁ , 27 ₂ are supplied to the first and second low-pass filters 21 ₁ , 21 ₂ .

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

Digital/analog audio/video signals can be used as playback signals.

〔Effect of the invention〕

According to the present invention described above, two-channel MR
A part of the circuit of the type magnetic head device, that is, the signal extraction circuit can be shared. An MR type magnetic head device can be obtained.

[Brief explanation of drawings]

1 and 2 are block diagrams showing embodiments of a magnetoresistive magnetic head device according to the present invention, and FIG. 3 is a sectional view showing the structure of a head portion of a conventional magnetoresistive magnetic head device. , Figure 4 is a block diagram showing the conventional magnetoresistive magnetic head device, Figure 5 is a characteristic curve diagram showing the magnetic field-resistance characteristics of the magnetoresistive magnetic sensing part, and Figure 6 is the previously proposed magnetic head device. 1 is a circuit diagram showing a resistive effect type magnetic head device. FIG. 3 ₁ , 3 ₂ are first and second bias conductors, 5 ₁ ,
5 ₂ are first and second magnetoresistive magnetic sensing parts, 21
₁ , 21 ₂ are first and second low-pass filters, 2
2 is a signal extraction means, 23 ₁ and 23 ₂ are first and second
is a multiplier.

Claims (1)

[Claims] 1 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 at the same frequency and at an angle of 90 degrees from each other. first and second bias magnetic field generation means that provide first and second alternating current bias magnetic fields having a phase difference; a signal extraction means for extracting a composite signal of signal outputs corresponding to the signal magnetic field; and first and second AC signals synchronized with the first and second AC bias magnetic fields and multiplying the composite signal by the first and second AC signals synchronized with the first and second AC bias magnetic fields; a second multiplication means; first and second low-pass filters to which respective outputs of the first and second multiplication means are supplied; A magnetoresistive magnetic head device characterized in that first and second signal outputs corresponding to the first and second signal magnetic fields are obtained.