Method for controlling bias current for magnetoresistive head, fixed magnetic recording device, and magnetic disc therefor

Abstract

It is an object of the present invention to enable a bias current for an MR head to be optimized as appropriate during an operation of a fixed magnetic recording device in order to restrain a possible asymmetrical distortion originating in a saturation in the reproduced signal from the MR head, thereby reducing the error rate during data read-outs. A fixed magnetic recording device according to the present invention comprises optimizing measurement means (10) for conducting measurements for optimizing a bias current value for the MR head in a head structure section (1) each time the MR head accesses a magnetic disc (2), and a microcomputer (8) for controlling optimizing measurement means (10) and outputting an instruction for updating of a bias current value for the MR head to the measured optimum bias current value for storage and an instruction for the supply of the updated and stored optimum bias current to the MR head.

Description

field of invention [0001] The invention relates to a method for controlling the bias current of a magnetoresistance magnetic head by utilizing the magnetoresistance effect, and a fixed magnetic recording device and its disk. Background of the invention [0002] To meet the increasing demand for recording density, recent stationary magnetic recording devices (HDD: Hard Disk Drive) use MR (Magnetoresistive) heads. MR heads are based on a reproduction method using the so-called magnetoresistive effect, in which the resistance of the MR head changes with an external magnetic field. Some HDDs use a combination MR / inductive head (comprising an MR head and a thin-film head in one piece). Combination MR / inductive heads use the thin-film head to write data and use an MR head adjacent to the thin-film head to read data. Therefore, for example, the MR head is characterized in that its reproduction output is larger than that of a thin-film head although it is dedicated to reading, and...

AI Technical Summary

Problems solved by technology

[0005] The first problem is: the resistance value of the head varies due to the spatial variability of the MR head

Although the variation distribution of the resistance values ​​of the heads corresponds to a standard distribution over a range of designed values, the resistance values ​​of the sensor portions of the individual MR heads are different

[0007] One problem caused by the large spatial variability is that having different heads within a device results in very different power losses

[0011] The second problem is that an electronic signal with a good signal-to-noise ratio depends on the design of the preamplifier

Variations in head resistance also limit the amount of bias current available for operation due to the voltage drop across the head and wires

If too much current is drawn through the high resistance head, the preamplifier stage will saturate and distort the signal, degrading its performance

[0012] The third problem is the gradual increase in resistance phenomenon (GRIP), which is related to the wires inside the MR head

Consequently, the device is considerably affected by noise, thereby also increasing the error rate of the reproduced signal

[0021] As mentioned above, one disadvantage of fixed magnetic recording devices using MR heads to read out data and to use detection amplitude reproduction methods such as partial response is that while it is known that not optimizing the bias current of the MR head may increase the error of this reproduced signal rate, but the best way to adjust the bias current of the MR head has not been established

The disadvantages of fixed magnetic recording devices using MR heads and detection peak return methods are similar to those of not optimizing the bias current of MR heads

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