JPS60138707A - Magnetic recording system - Google Patents

Abstract

PURPOSE:To make a read output stable by providing a current to a magnetic head and applying a magnetic field smaller than a write magnetic field to decrease magnetical deterioration of a recording signal against external disturbance. CONSTITUTION:A stabilized command is given to a constant current circuit 64 to generate a minute DC current, then a switching signal is given to a circuit 63 to change over alternately the polarity of the minute current. Moreover, a magnetic head 20' is moved at a low speed on the entire face of a disc 1, the minute current is given to a coil 60 to demagnetize the magnetic field on the disc 1. The demagnetized magnetic field is decreased more than the write magnetic field. As a result, a read output obtained from a medium 1 is made uniform and no change is caused by an external disturbance smaller than the demagnetized magnetic field.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a magnetic recording method for recording data on a magnetic recording medium using a magnetic head, and in particular to a method for reducing magnetic deterioration of data recorded in response to a disturbance magnetic field. The present invention relates to a magnetic recording system that can perform

[Technology background]

Magnetic recording is a method of recording information such as audio, video,
It is widely used in various fields of information processing. The principle of magnetic recording is that a magnetic recording medium containing a magnetic recording material is magnetized in a direction according to data using a magnetic head. Since this data is expressed as either "1" or "0", the magnetic recording medium is magnetized in a positive or negative direction depending on this data.

[Prior art and problems]

A magnetic disk device is known as a magnetic recording device for recording digital data. FIG. 1 is a configuration diagram of a magnetic disk device, in which there are multiple disks (three disks in the figure) centered around the shaft 13.
magnetic disks 10, 11.12 are provided, and the magnetic disks 10, 11, 12 are connected to a motor 1 around an axis 13.
Rotated by 4. On the other hand, the magnetic heads 20a to 20
d, 21a to 21d are mounted on a magnetic helad arm 20.21, and the arm 20.21 is supported by a carriage 30, which is driven by an actuator 40. These are covered with a housing 50. Therefore, by driving the actuator 40, the carriage 30
the magnetic head 2 at the tip of the arm 20.21.
0a to 20d, 21a to 21d as magnetic disks 10 to 1
The magnetic heads 20a to 2 are positioned in the radial direction.
Magnetic disks 10 to 12 by 0d and 21a to 21d
write data to or read data from the desired trunk.

Such a magnetic disk device has a floating magnetic head configuration as shown in FIG. to perform magnetic recording or reading.

This flying height is becoming smaller as the magnetic recording density improves, and has been reduced to about 0.2 μm. When a magnetic head approaches a magnetic recording medium (magnetic disk) in this manner, a phenomenon has occurred in which data recorded on the magnetic recording medium is disturbed by the presence of the magnetic head. For example, when an external leakage magnetic field LM is applied to a magnetic recording medium, this leakage magnetic field LM is concentrated by the core of the magnetic head at a location where the magnetic head is present, and the leakage magnetic field at this location becomes strong (and In addition, as the speed of the actuator 40 is expected to increase, there is a tendency to use a sintered alloy with a high magnetic field strength as a permanent magnet in the magnetic circuit used in the actuator 40. No matter how precise the manufacturing process is, adhesion of the ferromagnetic powder that is the material to gold cannot be avoided.

There is no problem as long as this continues to adhere to the actuator 40, but as the actuator 40 operates, this ferromagnetic powder may scatter and adhere to the core of the magnetic head 20, 21 as shown in the second figure. The magnetic flux of the ferromagnetic powder MP locally disturbs the magnetic recording medium 1. Furthermore, if a minute leakage current flows through the magnetic head for some reason, it will locally disturb the magnetic recording medium 1.

In this way, not all of the magnetic recording medium is disturbed, but the magnetization pattern of the places where the magnetic head has passed (that is, the places where it existed) is disturbed, so that the readout signal is not completely disturbed, as shown in Figure 3. There is a problem in that only a portion of the information appears to be missing, resulting in an error in reading this information. Therefore, as the gap between the magnetic head and the magnetic recording medium decreases, the external leakage magnetic field, ferromagnetic powder, and minute leakage current, which had no effect in the past, affect the magnetization of the magnetic recording medium. It is desired to solve this troublesome problem in which this effect does not affect the entire magnetic recording medium, but only where the magnetic head is located.

[Purpose of the invention]

An object of the present invention is to provide a magnetic recording system that can reduce magnetic deterioration of signals recorded on a magnetic recording medium due to such disturbances and stabilize continuous output.

[Structure of the invention]

To achieve the above object, the present invention includes a magnetic recording medium and a magnetic head, and after the magnetic head writes information to the magnetic recording medium, a magnetic field smaller than the write magnetic field is applied to the magnetic recording medium. It is characterized by adding

Further, embodiments of the present invention are as follows.

(2) A current is applied to the magnetic head to apply a magnetic field smaller than the write magnetic field.

(2) A magnetic field smaller than the write magnetic field is applied by a magnetic field applying means provided separately from the magnetic head.

(2) The magnetic field smaller than the write magnetic field is larger than the magnetic field caused by external disturbances.

(2) After the magnetic head writes a magnetization pattern in both forward and reverse directions according to information on the magnetic recording medium, a magnetic field, which is a front handle, is applied in a direction opposite to the direction of the recorded magnetization pattern.

(2) After writing positional information used for positioning control of the magnetic head onto the magnetic recording medium by the magnetic head, a magnetic field smaller than the write magnetic field is applied.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 4 is a detailed explanatory diagram of the present invention. In the figure, 60 is a coil, and the magnetic head 20 of the servo track writer
61 is an amplifier for amplification, 62 is a data write circuit that outputs a write current according to the data, and 63 is a switching circuit for stabilization. 64 is a constant current circuit that outputs a minute current of positive or negative polarity during operation, and generates a minute current in response to a stabilization command.

Next, the present invention will be explained using an example of writing a servo signal.

First, a servo signal is recorded on a servo trunk on one side of the magnetic disk 10, 11, or 12. for example,
A magnetic disk 12 is used for recording for servo tracks. This servo signal is subsequently read by the magnetic head 21d, and is used to position the magnetic head (that is, the actuator 40) based on this servo signal.

The patterns used as this servo signal are mainly so-called tri-bit patterns, gui-bit patterns, or patterns based on these. For example, a tri-bit pattern basically consists of an even pattern and an offset pattern, which are written alternately in the radial direction. When the magnetic head moves radially over these patterns alternately written with a predetermined radial pinch, even bit and odd bit outputs are obtained depending on the position of the magnetic head. The position signal is obtained by detecting the peak values of the even bit and the odd bit and taking the difference value between them, and is a triangular waveform signal having one period for two tracks, even and odd.

Therefore, before handing over the magnetic disk drive to the user, the manufacturer provides servo data to the data writing circuit 62 shown in FIG. A writing current is applied to the coil 60 via the amplifier 61 to write an even pattern and an odd pattern alternately in the radial direction.

The servo signal written in this manner may be partially disturbed by external disturbances as described above.

Therefore, the present invention performs the stabilization shown in FIG. 4(B).

That is, a stabilization command is given to the constant current circuit 64 to generate a minute direct current (for example, ±3.7 mA), and then a switching signal is given to the switching circuit 63 to alternately switch the polarity of the minute current. At the same time, the magnetic head 20' is moved evenly over the gold surface of the magnetic disk at low speed, and a minute current is applied to the coil 60 via the amplifier 61 to demagnetize the magnetic field on the first surface of the magnetic disk.

This effect will be explained with reference to FIGS. 5, 6, and 7.
The magnetic flux density B-magnetic field force curve of the magnetic recording medium 1 is as shown in Fig. 5, and the operating point is a near the saturation magnetic flux density on the AL cotton wire.
d is selected depending on the data "0" or "1". Then, when point a is brought to point b along the B-H curve by demagnetization by the magnetic field of opposite polarity described above, the new operating point becomes 0 point on the AL cotton line with a slope of μ=1. This demagnetization is caused by the magnetic recording medium 1
Since this is done over the entire surface, even if there is a missing part as shown in FIG. 6(A), the entire area is demagnetized so that the missing part disappears.

This will be explained in detail with reference to the enlarged view of the main part of the characteristics shown in FIG. 7. Due to the above-mentioned disturbance, the magnetic flux intensity at eight points originally decreases in level to point b' along the B-H curve. In other words, it will be reduced by ΔB'. On the other hand, magnetic recording medium 1
As a characteristic, once ΔB' decreases, the magnetic flux strength does not decrease even if a magnetic field less than ΔB' is applied. Therefore, the present invention demagnetizes the magnetic field (ΔB, ΔH) larger than the magnetic field (ΔH') due to the disturbance predicted in advance, brings the operating point to C, and then demagnetizes the magnetic field due to the disturbance at point C. This is to prevent the level from dropping, just by going back and forth between the two and the lights. That is, the operating point C is brought to the reversible region of the BH curve.

This demagnetizing field is of course smaller than the write field. By doing so, the readout output obtained from the magnetic recording medium 1, that is, the magnetic field strength becomes uniform as shown in FIG. 6(B), and does not change even if a disturbance magnetic field smaller than the demagnetizing magnetic field is thereafter applied. This read output is amplified by the amplifier 61 and the sixth
As shown in Figure (C), the level before demagnetization is restored. The optimum degree of this demagnetization is about 20 to 30% of the output of the recording magnetic field.

This method is considered to be a type of what is called stabilized demagnetization.

Although the above description is about demagnetization of the magnetic field in the positive direction, the above switching also causes the demagnetization of the magnetic field in the negative direction.

In this way, what applies to the servo trunk is that once the servo signal is written to the servo trunk, the! ,
This is because the deterioration due to disturbance cannot be recovered because the data is read-only and is not written again, and the effect of this deterioration is that the servo signal detects the peak value to obtain the position signal when it is read. This is because there is a risk that the position signal may be lost due to the direct sound. On the other hand, on the data surface where actual data is written, rewriting is performed, and the data is determined by slicing the read signal at a predetermined level, so there is less influence of deterioration due to disturbance. However, if it is applied to the data side as well, the reliability of the data will be further increased.

In the above explanation, it is explained that writing is performed on the servo disk in advance using the magnetic head of the servo trunk writer and demagnetization is performed, and reading of the servo track is performed without using a separate magnetic head (for example, 21d in FIG. 1). As explained in the configuration, a write head may be provided on the servo surface to perform servo writing and demagnetization, or servo signals may be written by servo trunk-like during manufacturing, or a magnetic field may be generated using a separate permanent magnet etc. Demagnetization may be effected by moving the means over the servo disk. Further, the process may be performed not only on the servo surface but also on the data surface. Furthermore, not only a floating head but also a contact type head may be used, and the magnetic recording medium is not limited to a disk, but may also be a Frembie disk or a tape.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, the present invention includes a magnetic recording medium and a magnetic head, and after the magnetic head writes information to the magnetic recording medium, a magnetic field smaller than the write magnetic field is applied to the magnetic recording medium. Because it is applied to the medium, there is no risk that the written information will partially deteriorate due to disturbances, and the magnetic field strength does not change even in the case of subsequent disturbances, which stabilizes continuous output. can be obtained.

For this reason, it is suitable as a countermeasure against disturbances that tend to occur in configurations in which the head and medium are close to each other and in configurations in which a ferromagnetic material such as samarium cobalt is used for the actuator, especially in recent years, in order to increase the speed of writing/reading. Reliability can be further improved. It is also very effective when applied to surfaces that are not rewritten, such as servo trunks.

Further, according to the present invention, the troublesome influence of such disturbances can be removed by a relatively simple method, which is an excellent practical effect.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a magnetic disk device, FIGS. 2 and 3 are explanatory diagrams explaining the problems to be solved by the present invention, FIG. 4 is a detailed explanatory diagram of the present invention, and FIG. 5 is an illustration of the present invention. A B-H characteristic diagram of the magnetic recording medium used in the invention, FIG. 6 is an explanatory diagram of the operation according to the invention, and FIG. 7 is an enlarged view of the main part of the characteristic shown in FIG. In the figure, 1-magnetic recording medium, 20.21-.magnetic head. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Akira Yamatani 241!1 ri 7 Figure 5, Figure f6

Claims (6)

[Claims] (1) A magnetic recording method comprising a magnetic recording medium and a magnetic head, and after the magnetic head writes information to the magnetic recording medium, a magnetic field smaller than the writing magnetic field is applied to the magnetic recording medium. . (2) The magnetic recording system according to claim (1), characterized in that a current is applied to the magnetic head to apply a magnetic field smaller than the write magnetic field. (3) The magnetic recording system according to claim (1), wherein a magnetic field smaller than the write magnetic field is applied by a magnetic field applying means provided separately from the magnetic head. (4) The magnetic recording system according to claim (1), wherein the magnetic field smaller than the write magnetic field is larger than the magnetic field caused by disturbance. (5) After writing a magnetization pattern in both forward and reverse directions on the magnetic recording medium according to information by the magnetic head, a magnetic field that is a front handle is applied in a direction opposite to the direction of the recorded magnetization pattern. Claim No. (1)
Magnetic recording method described in section. (6) After writing positional information used for positioning control of the magnetic head onto the magnetic recording medium by the magnetic head, a magnetic field smaller than the write magnetic field is applied to the magnetic recording medium. Magnetic recording method described in section. and