JPH06338005A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording/reproducing device capable of detecting with a large signal amplitude against a noise. CONSTITUTION:An MR element 1, an inductance element 2 and a capacitance element 3 constitute a parallel resonance circuit as described in the figure and equivalently represent an impedance 4, then by combining it with capacitances 5, 6 and transistor 7, a colpitts type oscillating circuit is formed. When the equivalent impedance 4 becomes inductive by the change of a resistance R of the MR element, this colpitts type oscillating circuit is oscillated, thereby a sine-wave oscillating signal is obtained on an output terminal 8. When the equivalent impedance 4 becomes capacitive by the change of the resistance R, the colpitts type oscillating circuit is not formed and the oscillation is stopped, then the signal is not appeared on the output terminal. As the whole constitution, the resistance R is changed by magnetization of the medium such as a magnetic tape, etc., therefore, the oscillating state or the oscillation stopped state is formed in accordance with this change, and conversely the signal of the magnetic tape, etc., is detected from these states.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for reading recorded information from a magnetic disk or a magnetic tape by utilizing a magnetoresistive effect.

[0002]

2. Description of the Related Art Conventionally, a magnetic reproducing element utilizing the magnetoresistive effect is described, for example, in Nishikawa: "Theory of Magnetic Recording", Asakura Shoten, 1986. July edition, page 9. That is, as shown in FIG. 4, an MR (magnetoresistive) element 1, a DC power source 13, a current limiting resistor 14, lead wires 15 and 16, a signal output terminal 1
7 and 18, and the MR is generated by the perpendicular magnetic field Hy generated from the medium magnetization 20 in the magnetic recording layer 19.
The magnetization of the element 1 changes from the i direction to the M direction as shown in FIG. 4, and the electric resistivity ρ of the MR element 1 is Δρ = Δρ _m cos ² θ (5) depending on the angle θ formed by i and M. It changes, and accordingly, the terminal voltage e of the MR element changes as shown in the equivalent circuit of FIG. 4B, and this is taken out as a reproduction signal. Note that Δρ _m is the maximum change amount of ρ.

Here, the MR element is a thin film of Ni-Fe or the like, which is previously passed from the DC power source 13 through the current limiting resistor 14.
A direct current of i is applied to the MR element 1 in parallel with the recording track width 21.

In practice, in order to increase the sensitivity and to improve the linearity, a bias magnetic field is externally applied as indicated by M ₀ in FIG.
_{When 0 is set} to 45 °, it comes to the middle point of the resistivity change represented by the equation (5) as shown in FIG.

The value of the total resistance R of the MR element 1 at this time is R
_When the operating angle θ changes by ± Δθ, the total resistance changes to (R ₀ ± ΔR). Conventionally, generally MR
Ni-Fe and Co-Fe used as the element 1
In the case of the above thin film, the value of ΔR / R ₀ is as small as 2-3%.

[0006]

As shown in the equivalent circuit of FIG. 4 (b), the conventional method of extracting the reproduction signal from the MR head utilizes the voltage induced across the MR element 1 as it is. Therefore, there were the following drawbacks.

That is, the change amount of the resistance component R of the MR element 1 is Δ
Let R be the ratio ΔR with the resistance R ₀ when the external magnetic field is zero.
Since the value of / R ₀ is 2-3%, the detection sensitivity is low.

The present invention has been made to solve the above problems, and magnetic recording / reproduction capable of detecting a large signal amplitude with respect to noise, rather than an output from only a resistance variable element which has only a weak change. The purpose is to obtain the device.

[0009]

In order to achieve the above object, a magnetic recording / reproducing apparatus of the present invention is characterized in that, in claim 1, a parallel resonance circuit comprising a magnetoresistive element, an inductance element and a capacitance element, and 2 A Colpitts type oscillation circuit in which a circuit in which two capacitance elements connected in series are connected in parallel is connected to a transistor, wherein a resistance change of the magnetoresistive element is converted into a change in reactance, and the Colpitts type oscillation circuit is provided. Oscillation output of
The data is read out as recorded information from the magnetoresistive element, and in claim 2, a magnetic resonance element, an inductance element, and a capacitance element (or a parallel resonance circuit including a magnetoresistive element, an inductance element, and a capacitance element). A Hartley oscillator circuit in which a transistor is provided with a circuit in which an inductance element connected in series with a parallel resonant circuit consisting of and a capacitance element are provided in a transistor, and the resistance change of the magnetoresistive element is converted into a change in reactance. Then, the oscillation output of the Hartley type oscillation circuit is read out as recorded information from the magnetoresistive element, and the parallel resonance circuit including a magnetoresistive element, an inductance element and a capacitance element, and Circuit with elements connected in series , A Colpitts type oscillation circuit connected to a transistor, wherein a resistance change of the magnetoresistive element is converted into a change of reactance, and an oscillation output of the Colpitts type oscillation circuit is recorded as information recorded from the magnetoresistive element. In addition, a Hartley oscillation circuit according to claim 4, wherein a parallel resonance circuit including a magnetic resistance element, an inductance element, and a capacitance element and a circuit in which an inductance element is connected in series are connected to a transistor. Therefore, the change in resistance of the magnetoresistive element is converted into a change in reactance, and the oscillation output of the Hartley oscillation circuit is read out as recorded information from the magnetoresistive element.

[0010]

According to the present invention, a variable resistance element such as a magnetoresistive (MR) element is combined with an inductance and a capacitance element to form a resonance circuit, and a resistance change is converted into a change in reactance. A weak resistance change is converted into the presence or absence of oscillation by satisfying the conditions close to the oscillation conditions of the oscillating circuit, thereby significantly improving the detection sensitivity of the external magnetic field.

[0011]

【Example】

(Embodiment 1) FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the figure, 1 is an MR element, 2 is an inductance element, 3 is a capacitance element, and these constitute a parallel resonance circuit as shown in the figure, equivalently configure an impedance 4, and combine capacitances 5 and 6. Is connected between the base and collector of the transistor 7 to form a Colpitts type oscillation circuit.

When the equivalent impedance 4 becomes inductive due to the change of the resistance R of the MR element 1, this Colpitts type oscillation circuit oscillates and a sine wave oscillation signal is obtained at the output terminal 8. On the other hand, when the resistance R is also changed to be capacitive, the Colpitts oscillator circuit is not configured in FIG. 1, the oscillation is stopped, and the signal does not appear at the output terminal. In the entire configuration, the resistance R changes due to the magnetization of the medium such as the magnetic tape, so that the change causes the circuit of FIG. .

Next, the operation of the equivalent impedance 4 surrounded by the dotted line frame in FIG. 1 will be described in detail.

Impedance Z as seen from terminals 11 and 12
Is Z = [{(R + jωL) / jωC} / {R + jωL + (1 / jωC)}] = [R + jω {L (1-ω ² LC) -CR ² }] / {1-ω ² (LC + C ² R ² )} (1), and the reactance component X is X = ω {L (1-ω ² LC) -CR ² } / {1-ω ² (LC + C ² R ² )} (2). Here, the resistance R is ± ΔR with R ₀ as the center value.
When it changes, it is represented by R = R ₀ ± ΔR (3), and the equation (2) is expressed by X = ω {L (1-ω ² LC) -C (R ₀ ± ΔR) ² } / [1- ω ² {LC-C ² (R ₀ ± △ R) ² }] (4) The reactance is changed as shown in FIG. 3 with the angular frequency omega, the change, as when the R = R ₀ shown by a solid line, when the R = R ₀ + △ R as shown by the broken line,
When R = R ₀ −ΔR, it becomes as indicated by the alternate long and short dash line.
That is, the reactance component of the equivalent impedance 4 at a specific angular frequency can be made inductive or capacitive by changing R.

In FIG. 3, ω_R0Is R = R₀of
When, the angular frequency at which the denominator of equation (4) becomes zero, ω _{+ △ R}Is R
= R₀Angular frequency where the denominator of equation (4) becomes zero when + ΔR
Number, ω _{-△ R}Is R = R₀-When ΔR, the denominator of equation (4) is zero.
Is the angular frequency. Then, the hatched lines in FIG.
In the range where the valence impedance 4 becomes inductive
Only the Colpitts oscillator of Fig. 1 oscillates, so
R value (R_CAnd oscillates in the range of R larger than
Sea urchin circuit constants L, C, C₁, C₂Can be set. This
4A, the medium of the magnetic recording device 19
Depending on the strength of the magnetic field Hy perpendicular to the medium surface due to the magnetization 20,
Since the resistivity ρ of the R element 1 changes as shown in equation (5),
Medium magnetization 20 and oscillation of oscillation circuit of FIG. 1 and oscillation stop
Of the medium magnetization as shown in FIGS.
The orientation of the medium magnetization 20 can be detected by adjusting the polarity.
You can get out.

(Embodiment 2) FIG. 2 is a circuit diagram showing a second embodiment of the present invention. Further, in FIG. 2, the same reference numerals are given to those having the same or the same functions as those in FIG. That is, in this embodiment, a Hartley type oscillation circuit is used instead of the Colpitts type oscillation circuit of FIG. In the example shown in FIG. 2, the equivalent impedance 4, the reactance component is, is operating in a range of the inductive and also forms the oscillation circuit as L _2, instead of placing the L ₁ in equivalent impedance 4 Oscillation A circuit can also be configured.

(Third Embodiment) Although not shown as a third embodiment of the present invention, there is the following one. That is, the first
In the second embodiment, the reactance component of the equivalent impedance 4 uses the inductive range shown in FIG. 3, but the capacitive range shown in FIG. 3 may be used.

As a concrete example, in this case, the equivalent impedance 4 is replaced with C ₁ of 5 or C ₂ of 6 of the Colpitts type oscillation circuit of FIG. 1, and C'of 10 of the Hartley type oscillation circuit of FIG. Will be used instead of.

[0019]

As described above, the present invention has a new function of signal output (amplitude:
Instead of several mV), a large effect (improvement in detection sensitivity) of the presence or absence of oscillation of a high-frequency high-frequency signal (amplitude: several V) depending on the magnetization direction of the recording medium is obtained.

Further, in order to improve the performance and efficiency, instead of the method in which the thermal agitation noise is large due to only the resistance change, the resistance change is converted into a reactance change, and a signal detection with a large signal amplitude vs. noise such as the presence or absence of the oscillation of the high frequency signal is detected. A method can be provided.

[Brief description of drawings]

FIG. 1 is a Colpitts oscillator circuit diagram of a first embodiment of the present invention.

FIG. 2 is a Hartley oscillator circuit embodying the present invention.

FIG. 3 is a diagram showing a reactance component when a resistance R of an element of a resonance circuit including a magnetoresistive (MR) element, which is a basis of the present invention, changes.

FIG. 4 is a diagram showing an operating principle of a signal reproducing head using a conventional MR element.

FIG. 5 is an explanatory diagram showing a method of operating a conventional MR element with improved sensitivity and linearity.

FIG. 6 is a diagram showing the relationship between the polarity of the recording medium magnetization and the oscillation state of the circuits of FIGS. 1 and 2.

[Explanation of symbols]

1 Magnetoresistive (MR) element 2 Inductance forming equivalent impedance 3 Capacitance 4 Equivalent impedance 5,6 Colpitts type oscillation circuit forming capacitance 7 Transistor 8 Oscillation output terminal 9, 10 Inductance and capacitance forming Hartley type oscillation circuit respectively 11, 12 Equivalent impedance terminal 13 DC power supply for MR element 14 Current limiting resistance 15, 16 Lead wire 17, 18 Signal output terminal 19 Magnetic recording layer of medium such as disk or tape 20 Medium magnetization Hy Medium of medium surface by medium magnetization Vertical component of magnetic field i Direction of rotation of magnetization of MR element by current M Hy flowing in MR element by DC power supply Signal output generated between angle e 17 and 18 formed by θ i and M 21 Recording on magnetic recording layer track width M ₀ M Increment from the center value _{θ 0 M 45 ° + △ θ} θ 0 at an angle of ₀ - decrement from △ theta theta ₀

Claims (4)

[Claims] 1. A Colpitts oscillator circuit is constructed by connecting a parallel resonance circuit composed of a magnetoresistive element, an inductance element, and a capacitance element, and two parallel-connected capacitance elements in parallel to a transistor. By converting the resistance change of the magnetoresistive element into a change of reactance to control the oscillation condition, the resistance change of the magnetoresistive element due to the recorded information is converted into the presence or absence of the oscillation output of the Colpitts type oscillation circuit, A magnetic recording / reproducing apparatus characterized by reading recorded information. 2. An inductance element connected in series with a parallel resonance circuit composed of a magnetic resistance element, an inductance element, and a capacitance element, and a capacitance element,
Is connected in parallel to a transistor to form a Hartley oscillation circuit, and the resistance change of the magnetoresistive element is converted into a change in reactance to control the oscillation condition, whereby the magnetoresistive element based on recorded information is controlled. The magnetic recording / reproducing apparatus is characterized in that the recorded information is read by converting the resistance change of the above into the presence or absence of the oscillation output of the Hartley type oscillation circuit. 3. A Colpitts oscillator circuit is formed by connecting a parallel resonance circuit including a magnetoresistive element, an inductance element, and a capacitance element and a capacitance element connected in series to a transistor to form a Colpitts type oscillation circuit. To change the resistance change of the magnetoresistive element due to the recorded information into the presence or absence of the oscillation output of the Colpitts type oscillation circuit to read the recorded information. And a magnetic recording / reproducing apparatus. 4. A Hartley oscillation circuit is formed by connecting a parallel resonance circuit composed of a magnetic resistance element, an inductance element, and a capacitance element, and a circuit in which an inductance element is connected in series to a transistor to form a Hartley oscillation circuit. To change the resistance change of the magnetoresistive element due to the recorded information to the presence or absence of the oscillation output of the Hartley type oscillation circuit to read the recorded information. Characteristic magnetic recording / reproducing device.