JPS60119616A - Method of biasing mr head - Google Patents

Abstract

PURPOSE:To enlarge rproduction output of an MR haed by controlling conduction current of a conductor utilizing a part of reproduction output of the MR head. CONSTITUTION:When deflection of a magnectic field curve 29 generated from a magnetic tape is minute and FET 24 is off, a bias magnetic field is as small as H2. Accordinging, even if an output amplifier 22 operates, reproduction output is merely enlarged with distorted state as shown by a curve 30. When the reproduction output is inputted to FET 24 through a feedback amplifier 27, conduction current to a conductor film 9 changes, and the bias magnetic field is corrected to optimum H1, and a reproduction output curve 31 that coincides with a curve 16 is obtained. When a high frequency recording magnetic field such as a curve 32 is further applied to the MR head 20, an operation point 33 moves on a curve 12 to a bias magnetic field H3 where faithful reproduction can be made surely without distortion, and reproduction output of a curve 34 is obtained. At this time, the operation point 33 moves properly within the limit of an optimum bias area A according to frequency band.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a bias control technique for an MR head in which magnetic field bias is applied by a conductor in the MR head.

BACKGROUND ART Conventionally, MR heads differ from inductive thin film magnetic heads,
Reproduction is possible without depending on the moving speed of the magnetic recording medium,
In addition, multi-head patterns can be easily formed using vacuum evaporation and sputtering methods, which are established as semiconductor device manufacturing technologies, so DAT for POM magnetic recording
It has been used as a magnetic playback head for devices such as digital audio recorders. That is, to show the structure of a general 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 is shown in FIG. 2 as a perspective view. In other words, in FIGS. 1 and 2, substrates such as glass or sapphire,
2 is a first magnetic shield layer made of a ferromagnetic alloy such as permalloy that corresponds to all multi-head positions, 3 is an insulating and non-magnetic film such as 5102 film or Al2O3 film, and 4 is 8102 film or Al2O3 film 3. The MR thin film pattern is adhered onto the first magnetic shield layer through the MR thin film pattern, and is formed in a long and narrow stripe shape along the surface facing and in contact with the magnetic tape 5 as a magnetic recording medium shown in FIG. 2, that is, along the paper surface. This is a permalloy thin film pattern. Furthermore, 6.7 is a striped thin film pattern 40 both ends 4L, 4
This is a conductor pattern of Au or Al that is led out from R to the surface opposite to the polished surface of the head. 8 is a SiO□ film or A12'03 film similar to figure number 3, and 9 is an MR thin film pattern 4 that can respond linearly with little distortion to changes in the external magnetic field generated by the magnetic tape 5. 10 is a SiO□ film or A7!203 film similar to those shown in figures 3 and 8, and 11 is a second magnetic shield layer.

By the way, the MR head having the above-mentioned structure is a reproducing head in magnetic recording that fully utilizes the magnetoresistive effect.
When the relationship between the magnetic field H from the recording medium and the electrical resistance R of the MR thin film pattern 4 is illustrated, a chevron curve 12 symmetrical to the R axis is drawn as shown in FIG. Due to the changing state of the magnetic domain recorded on the magnetic tape 5, if we try to reproduce only the MR thin film pattern 4 in 2018, the magnetic field change curve 13 from the magnetic tape 5
is deflected to H-0, that is, the entire center of the R axis, and is reproduced as a curve 14 due to the relationship of the R-H curve 12, and faithful reproduction is not performed. Therefore, in the MR head, the entire conductor film 10 provided near the MR thin film pattern 4 is energized, and the bias magnetic field H1 is applied to the MR thin film/' turn 4 to superimpose it on the curve 13 to create the entire curve 15. 16, faithful reproduction without distortion is performed. However, if the magnetic field from the magnetic tape 5 is minute, the magnetic field change curve 17 that swings around H-H, all centers, will still be reproduced as a minute curve 18, which is a weak point that makes it difficult to obtain an output of a predetermined magnitude. was there.

DISCLOSURE OF THE INVENTION Purpose of the Invention This invention was proposed for the purpose of resolving the lack of reproduction output expansion in the above-mentioned MR head.
The purpose is to make full use of the entire effective region of the rR-H curve, which shows the relationship between the R element and the electrical resistance R.

Structure of the Invention This invention uses a conductor in the vicinity of an MR element to generate a bias magnetic field generated by energizing the conductor, which is applied to the MR element.
Regarding the head, the structure is such that all of the reproduction output of the MR head is utilized to fully control the current flowing through the conductor. In other words, the present invention applies the full bias magnetic field in accordance with the reproduction output in order to solve the insufficient expansion of the reproduction output of the MR head.

Effects of the Invention If the present invention is fully implemented, not only a reproduction output of a predetermined magnitude can be obtained even when the magnetic field is smaller than that of a magnetic recording medium, but also the following advantages are exhibited. In other words, according to the present invention, even when all magnetic recording is performed in a high frequency band, a reduction in reproduction output can be prevented, and moreover, fidelity can be compensated.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 4 is a diagram showing the operating principle of an MR head for fully 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 FIG. 1 and FIG. 7 is the power supply V through all the voltage dividing resistors 21
. . It is also connected to the output amplifier 22. Furthermore, one end of the conductor film 9 is a diode 2.
The other end is connected to the anode of the conductor @9 through 1!
It is connected to the source terminal of the FEiT 24 for controlling the It flow. Note that the cathode of the diode 230 mentioned above is connected to ground. Here, FIUT2 as a current control means
4, the drain terminal is connected to the power supply V via a resistor 25. . and the drain and source terminals are connected to MR.
The head 20 is connected with a constant resistor 26 so that a bias magnetic field can be applied even when the head 20 starts operating. Also FE
The gate terminal of T24 is connected to the output of a feedback amplifier 27 that amplifies part and all of the reproduced output from the output amplifier 22 to have an opposite phase. Therefore, the input of the feedback amplifier 27 is
It is connected to the output of the output amplifier 22 and to the reproduction output terminal 28 .

Now, when operating the MR head 20 based on the operating principle of the MR head 20 described above, referring to FIG. High-fidelity playback output can be obtained. First, when the deflection of the magnetic field curve 29 generated by the magnetic tape 5 is minute and the FET 24 is OFF, the bias magnetic field H2 is small, so even if the output amplifier 22 is activated, the playback output is 1 as shown by the curve 30. It just remains distorted and magnified. Therefore, when the reproduced output is inputted to the FET 24 via the feedback amplifier 27, the current flowing through the conductor film 9 changes, the bias magnetic field is corrected to the optimum Hl, and the reproduced output curve matches the curve 16. 31 is obtained. Further, when a high-frequency recording magnetic field as shown by curve 32 is applied to the MR head 20, the operating point 3 on curve 12 is reached until the bias magnetic field H3 allows reliable reproduction without distortion.
3 is moved, and a reproduced output of curve 34 is obtained. Incidentally, at this time, the operating point 33 moves appropriately within the optimum bias region A depending on the frequency band.

In the above embodiment, the FIT was used as the current control means for the conductor to which the entire bias magnetic field was applied, but in this invention,
In addition, if necessary, the feedback amplifier may be completely modified and a power transistor, thyristor, etc. may be used.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the contact surface of a general MR head facing the recording medium, Fig. 2 is an enlarged perspective view thereof, and Fig. 3 shows the HFJfim and input magnetic field of the M'R head. The characteristic curve diagram showing reproduction output waveform 7 and FIG. 4 are diagrams of the operating principles of the MR head for fully explaining one embodiment of the present invention. 4...MR element (MR thin film pattern), -9... Conductor (conductor film), 20...MR head, 22...Output amplifier, 24...ii current control means FET), 27...Feedback amplifier.

Claims (1)

[Claims] Regarding an MR head that applies current to a conductor provided near an MR element and applies the generated magnetic field as a bias magnetic field,
A method for biasing an MR head, characterized in that the entire current of the conductor can be controlled by a part of the reproduction output of the R head.