JPH01245411A - Magnetic head - Google Patents

Abstract

PURPOSE:To make the width of the reproducing track of a magnetic head narrower than that of the recording and/or erasing track by deteriorating the magnetic characteristics of the parts of magnetic core sections corresponding to each other on both ends of the gap in the track width direction so that they can participate in the recording and/or erasure, but not in reproduction. CONSTITUTION:The magnetic characteristics of the parts of magnetic core 12 sections corresponding to each other on both ends of a gap 11 in the track width direction are deteriorated so that they can participate in the recording and/or erasure, but not in the production. Since the sections 15 where the magnetic characteristics are deteriorated on both ends of the gap 11 in the track width direction do not participate the reproduction practically at the time of reproduction due to the gap length and spacing losses at the magnetic characteristic deteriorated sections 15, widths of the sections 15 act as off-track margins. Since noises or signals are not reproduced even if an off-track is produced at the time of reproduction when the off-track is within the range of the off- track margins, the SN does not drop. Thus the reproducing track width can be made narrower than the recording and/or erasing track width.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording/reproducing magnetic head capable of increasing the off-track margin during reproduction.

[Prior Art] When recording and reproducing data using a magnetic head for both recording and reproducing purposes, there is a problem in that the SN ratio decreases due to off-track conditions. FIG. 6 shows a decrease in the S/N ratio based on off-track, and after forming the first recording track 1, when forming the second recording track 2, the center of each track 113. Shifted to 4 (off track)
When this occurs, an unerased area 1a of the first recording shown with diagonal lines is generated and juxtaposed with the second recording track 2. If the second recording track 2 can be accurately scanned by a recording/reproducing magnetic head consisting of a core 6 having a gap 5 and a coil (not shown), no problem will occur; If the head position shifts (off-track) as shown in FIG. A mixed output with the reproduced component 1a is obtained, resulting in a poor S/N ratio.

To solve this kind of problem, the magnetic head of a typical floppy disk device employs a tunnel erase head structure. This tunnel erase head has erasing heads on both sides of the magnetic head for both recording and reproduction, and erases both sides of the recording track during recording, so even if racking to OFF 1 occurs during reproduction, the S/N ratio will not deteriorate much. However, In order to provide an erasing head, the tunnel erase type head requires
The structure is inevitably complicated and expensive. In addition, a magnetic head that solves the problem of off-track without relying on a tunnel erase type head, which cannot perform high track density recording with a tunnel erase type head, is disclosed in, for example, Japanese Patent Laid-Open No. 61-59613. The gap length is narrowed at the center in the track width direction and widened at both ends, so that the narrow gap length at both ends participates in recording and/or erasing, but does not substantially participate in playback. There is something I did.

[Problems to be Solved by the Invention] However, it is extremely difficult to vary the narrow gap length of about 2 μm depending on the location, and it has not been possible to easily manufacture the gap length.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording/reproducing magnetic head that can easily make the reproducing track width narrower than the recording and/or erasing track width.

[Means for Solving the Problems] To achieve the above object, the present invention provides a recording and reproducing magnetic field comprising a magnetic core including a gap having a substantially uniform gap length, and a coil wound around the magnetic core. In the head, the magnetic properties of the magnetic core portions corresponding to both ends of the gap in the track width direction are degraded so that they participate in recording and/or erasing but do not substantially participate in reproduction. This relates to a magnetic head that uses

[Function] In the present invention, the portions with degraded magnetic properties at both ends in the track width direction are involved in recording and/or erasing, but during reproduction, the portions with degraded magnetic properties are affected based on the gap length loss and spacing loss in the portions with degraded magnetic properties. The width of this portion with degraded magnetic properties serves as an off-track margin, since it does not substantially participate in reproduction.

Therefore, even if off-track occurs during playback, as long as it is within the above-mentioned off-track margin, no extra noise or signal will be played back, so there is virtually no reduction in the S/N ratio, and the core gap length Since the magnetic properties of the core having a uniform gap length are only locally degraded instead of being changed depending on the location, it can be easily manufactured with high precision.

[Embodiment] Next, a magnetic head of a floppy disk device according to an embodiment of the present invention will be explained with reference to FIGS. 1 to 5. The recording/reproducing magnetic head 10 shown in FIG.
1 and a coil 13 wound around the core 12. gap 1
The first portion 12a and the second portion of the core 12 are opposite to each other through the
The portions 12b are adhered to each other by a non-magnetic material 14 made of glass filled in the gap 11.

The gap length (gap width) L in the gap 11 is the same regardless of the change in position in the track width direction, similar to a general magnetic head. However, the first and second
Magnetic property deterioration portions 15 are provided at both ends of the portions 12a and 12b in the track width direction. This magnetic property deterioration part 1
Reference numeral 5 denotes a portion whose saturation magnetic flux density and magnetic permeability are lowered by applying a laser beam, and which can be recorded and/or erased, but is not substantially involved in reproduction. Therefore, as shown in FIG. 2, the recording track width Wa is obtained corresponding to the width of the core 12, but the reproduction track width W
b is a value obtained by subtracting the width of the magnetic characteristic deteriorated portion 15 from the recording track width Wa. Note that the magnetic characteristic deterioration section 15 has the effect of making the gap length pseudo-wider, and during reproduction, it is not possible to perform magnetic flux detection that contributes to the reproduction output due to gap length loss and spacing loss. However, since the problem of gap length loss does not occur during recording or erasing, recording or erasing is possible via the magnetic property deterioration section 15.

3 and 4 show a method of manufacturing a magnetic head. 1st
A ferrite block 16 and a second ferrite block 17 are bonded with a non-magnetic material 14 through a gap 11, a laser beam mask 18 is placed on the top surface, and a laser beam is emitted through the hole 19 of the mask 18. 20 is projected so as to correspond to both ends of the track of each magnetic head. That is, as shown in FIG. 4, a ferrite block 16.
Cutting line 21 and gap 1 shown by broken line 17
The vicinity of the intersection with 1 is heated by the laser beam 20. In addition, local heating is performed in an oxidizing atmosphere (in air or active oxygen).
Do it with The crystal structure of ferrite is spinel (5 pin
el ) lattice, and when oxygen enters the spinel lattice due to heating, the lattice structure collapses and the magnetic properties (
A decrease in saturation magnetic flux density and magnetic permeability occurs.

As shown in FIG. 4, by projecting the laser beam 20 on the ferrite blocks 16 and 17 before cutting, the magnetic property deteriorated portion 15 can be easily and accurately obtained.

FIG. 5 explains off-track during recording and reproduction by the magnetic head 10 shown in FIG. 1. After forming the first recording track 1 by passing a recording current through the magnetic head 10, when forming the second recording track 2 overlappingly, if a shift occurs between the track centers 113.4, the first A shaded portion 1a of the recording track 1 for the first time is an unerased portion. Note that the magnetic head 10
The width of the recording track 1.2 is determined by the magnetic property deterioration portion 15.
Despite the existence of the gap 11, the track width becomes wider than the center portion of the track width.

When reproducing the second recording track 2 with the magnetic head 10, even if the magnetic head 10 shifts to the same position as the first recording track 1, as shown by the dotted line, it almost corresponds to the maximum off-track value. Since the magnetic characteristic deteriorated portion 15 is formed to have a width of
is not scanned, therefore, the reproduced output does not include noise based on the unerased portion 1a, and the S/N ratio does not decrease.

In FIG. 5, the second recording track 2 is formed on top of the first recording track 1, but before forming the second recording track 2, the magnetic head 10 is operated in the erase mode to erase the data. The second recording track 2 may be formed after scanning.

[Modifications] The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.

(1) Instead of locally projecting a laser beam to form the magnetic property deterioration area 15, an electrode is placed facing the magnetic property deterioration area, and the core 12 is locally formed by discharging an oxidizing atmosphere. The magnetic property deteriorated portion 15 may be formed by heating.

(2) Projecting a laser beam onto the cutting line 24 of the gap forming surface 23 of the ferrite block 22 for making the C-shaped core shown in FIG. It may be formed entirely in the horizontal direction.

(3) The first portion 12 of the core 12 as shown in FIG.
The magnetic property deterioration portion 15 may be formed only on the a side.

(4) It is also applicable to the case where the core 12 is formed by laminating a large number of magnetic layers.

(5) It is also applicable to heads of fixed magnetic disk drives. It is also applicable to magnetic heads of magnetic tape devices.

(6) The magnetic property deteriorated portion 15 may be a portion in which only the magnetic permeability is reduced without substantially reducing the saturation magnetic flux density.

[Effect of the invention] As described above, according to the present invention, recording and/or erasing!・
Magnetic heads with different rack widths and reproduction track widths can be easily provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a part of a magnetic head according to an embodiment of the present invention, FIG. 2 is a plan view of the magnetic head shown in FIG. 1, and FIG. 3 is a sectional view showing a method of manufacturing the magnetic head. Fig. 4 is a perspective view showing a ferrite block with deteriorated magnetic properties formed before cutting, Fig. 5 is a view showing the relationship between the magnetic head of this embodiment and the track, and Fig. 6 is a conventional magnetic head. FIG. 7 is a diagram for explaining a method of manufacturing a magnetic head of a modified example. FIG. 8 is a plan view of a magnetic head of a modified example. 10...Magnetic head, 11...Gap, 12.-
- Core, 13... Coil, 15... Magnetic property deterioration part.

Claims (1)

[Claims] [1] In a recording/reproducing magnetic head comprising a magnetic core including a gap with a substantially uniform gap length and a coil wound around the magnetic core, magnetic core portions corresponding to both ends of the gap in the track width direction. 1. A magnetic head characterized in that the magnetic properties of the head have been degraded so that it participates in recording and/or erasing but does not substantially participate in reproduction.