JPS60119617A - Method of biasing mr head - Google Patents

Abstract

PURPOSE:To reduce power consumption by driving a switching device that lets current flow to a conductor by a part of reproducing output of an MR head. CONSTITUTION:When the MR head 20 slides on a part of a magnetic tape on which recording is not made, the bias magnetic field is ''O'', and resistance R ofa MR thin film pattern 4 is constant. Accordingly, constant low output level is taken out from a terminal 27 through an output amplifer 22. When, application of a magnetic field H is started from the magnetic tape and a waveform curve 29 acts on the MR thin film pattern 4, output that follows the output waveform curve 30 appears in the terminal 27, and at the same time, inputted to the gate terminal of an FET 24 through a voltage feedback circuit 26 as a specified output level. That is, gate source voltage above threshold level is applied to conduct the FET 24. Desired bias magnetic field Ho is generated by appling fixed drain current to a conductor film 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a technique for applying a fully effective magnetic field bias using a conductor in a IIIR head.

BACKGROUND ART Conventionally, MR heads differ from inductive thin film magnetic heads,
POM magnetic recording media can be reproduced without depending on the moving speed of the magnetic recording medium, and multi-head patterns can be easily formed using vacuum vaporization and sputtering methods, which are established as semiconductor device manufacturing technologies. Do: DA
It has been praised as a magnetic playback head for devices such as T (digital audio tape recorder). That is, to illustrate the details of a typical MR head, the polishing surface that faces and contacts the magnetic tape is shown in cross section as shown in FIG. 1, and the three-dimensional structure follows the perspective view shown in FIG. 2. . In other words, the first
In the figure and FIG. 2, 1 is a substrate made of glass or sapphire, 2 is a first magnetic shield layer made of a ferromagnetic alloy such as permalloy, and is made resistant to high-resistance multi-heads, and 3 is an insulating and non-magnetic material. For example, 8101 film or ALIOI film,
4 is a 9 MR thin film pattern which is adhered to the first magnetic shield layer through a 5102 film or an ALsOI film 3', and is in contact with the magnetic tape 5 as a magnetic recording medium shown in FIG. In other words, it is a permalloy thin film pattern formed in elongated stripes along the paper surface. Furthermore, 6,
7 is a striped thin film pattern 40 at both ends 4 TJ;
4 This is an Au or Al conductor pattern led out to the surface opposite to the polished surface of the RJ-rehead. 8 is a SiO+ film similar to figure 3, Al, 0. The film 9 is a conductive film for applying a DC bias 7 so that the MR thin film pattern 4 can respond directly to changes in the external magnetic field generated by the magnetic tape 5 with little distortion; The S10° film or Al1ros film similar to numbers 3 and 8, and 11 are the second magnetic shielding layers.

By the way, the MR head having the above structure is a reproducing head for magnetic recording using the magnetoresistive effect k+6, and the relationship between the magnetic field H from the recording medium and the electrical resistance R of the MR thin film nozzle 4 is shown below. , all 12 chevron curves symmetrical to the R axis are drawn as shown in FIG. When this MR head reproduces all the states of the magnetic domains recorded on the magnetic tape 5, which is a recording medium, P is approximately linearly approximated in the curve 12 in order to perform faithful n+4 reproduction. A current is applied to the conductor film 9 over the entire area so that the operating point is set at the operating point, and the entire magnetic field H8 generated is superimposed on the magnetic field H generated from the magnetic tape 5. If the waveform of the magnetic field H is curve 13, the reproduced output waveform is obtained as curve 14 with less distortion.

However, the MR head has no (Iass magnetic field H6
Continuing to apply the entire current to the conductor film 9 in order to apply the entire voltage V
C, and as mentioned earlier, POM recording is often performed and the entire multi-head is formed, so the MR thin film pattern 4
It has the disadvantage that it requires significantly more power than the conventional drive. Furthermore, since the conductor film 9 is placed close to the MR thin film pattern 4, there is a risk that the current during bias application will cause the entire MR thin film pattern 4 to be overheated unnecessarily and the degree of change in its electrical resistance R will be completely reduced. there was.

DISCLOSURE OF THE INVENTION OBJECTS OF THE INVENTION The purpose of the present invention is to eliminate all of the drawbacks of the MR head described above and to reduce power consumption.

SUMMARY OF THE INVENTION In order to achieve all of the above-mentioned objects, the present invention relates to an MR head in which a magnetic field generated by energizing a conductor provided near an MR element is applied as a total bias magnetic field. In other words, in this invention, when there is no magnetic field from the recording medium, there is no need to apply a bias magnetic field to the MR element, so that the conductor is not energized. This is what you set.

Effects of the Invention When the present invention is fully implemented, the bias magnetic field can be applied only when the MR head reproduces output, the magnetic field bias is effectively utilized, and the power consumption of the MR head can be reduced. Further, according to the present invention, an optimum partial bias magnetic field can be applied by the switching means, so that a faithful reproduction output is possible.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 4 is a diagram illustrating the operating principle of an MR head for explaining an embodiment of the present invention. First, 20 surrounded by a dashed line
is a magnetic field bias type MR head using a general conductor as explained in Figs. 1 and 2, and the MR element Ml
Of the conductor patterns led out from both ends of the thin film batt 4, 6 is grounded, and 7 is connected to the power supply V through the voltage dividing resistor 21. . It is also connected to the output amplifier 22. Furthermore, one end of the conductor film 9 is connected to the anode of the diode 23, and the other end is connected to the anode of the conductor film 9.
11 i! It is connected to the source terminal of a switching FET 24. Note that the cathode of the diode 23 mentioned above is connected to ground. Here, the FET 24 as a switching means has its drain terminal connected to the power supply V0° through the resistor 25, and its gate terminal connected to the output A
A part or all of the reproduced output from the circuit 22 is connected to the output of a voltage 'jM return circuit 26 for clipping and rectifying. Therefore, the input of the voltage)Ii4M circuit 26 is connected to the reproduction output terminal 28 along with the output of the output amplifier 22.

A case in which the MR head 2o is operated according to the operating principle of the MR head 2o described above will be described below without referring to FIG. 3 in its entirety.

First, when the partial sound MR head 20 on which the magnetic tape 5 is not recorded slides, the bias magnetic field is O, and the MRM
The resistance B of the film pattern 4 is constant, and only a constant low output level is taken out from the terminal 27 through the entire output amplifier 22.

At this time, a part of the output is sent to the FET via the voltage feedback circuit 26.
24 gate terminals are added, but in this case the gate terminal
Source voltage V. Since S is minute, FET24 cannot be traced,
Therefore, the conductor film 9 is not energized and the bias magnetic field is up to 0σ)ai. At that moment, the magnetic field H starts to be applied from the magnetic tape 5, and the waveform curve 29 corresponds to the MP thin film pattern 4.
, an output according to the output waveform curve 30 appears at the output terminal 27, and a predetermined output level is output to the gate terminal of the FET 24 through the entire voltage feedback circuit 26. Gate-source voltage V. S is applied, F]IcT 24 conducts, and a constant drain current is applied to the 'fr conductor film 9, thereby generating a desired bias magnetic field H8. Therefore, the waveform curve 29 is superimposed on H-Ho, and the output waveform curve m31
It is extracted as an output according to the following. moreover)
When the MR head 20 slides until the magnetic field H of the magnetic tape 5 becomes 0, the output level decreases and the FET no longer conducts.

In the above embodiment, PETTh was used as a switching means for flowing current 'tM'fr to the conductor, or in this invention,
In addition, for example, the design of the current feedback circuit may be changed to include power transistors in all phases, or thyristors may be used exclusively.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the opposing contact surface Mk of a general MR head with a recording medium, FIG. 2 is an enlarged perspective view thereof, and FIG. 3 is an R-8 curve and an input magnetic field of the MR head. FIG. 4, which is a legibility curve diagram showing all reproduced output waveforms, is a diagram showing the operating principles of an MR head for fully explaining an embodiment of the present invention. 4...MR element (MR thin film pattern), 9...Conductor (conductor film), 20...MR head 1 22...Output amplifier 1 24...Switching means (FET), 26.Φ. feedback circuit.

Claims (1)

[Claims] Regarding the MR head, which applies a magnetic field generated by energizing a conductor provided near the MR element as a total bias magnetic field, the MR
MR characterized in that the switching means for causing the entire current to flow through the conductor is fully driven depending on the reproduction output of the head.
No(ias method) of the head.