JPH0432007A - Magnetic head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a magnetic head used in hard disk drives, VTRs, floppy disk drives, etc. for recording and reproducing. The present invention relates to a magnetic head in which a high saturation magnetic flux density thin film of metal, amorphous, etc. is formed on the gap forming surface on the outflow end side of the recording medium.

"Conventional technology" The basic concept of the old G structure of magnetic heads is
It is described in Publication No. 11642. In addition, there is also a device in which only the outflow end side of the recording medium has an MTG structure.
It is introduced in Publication No. 4625.

The MIG structure is, as shown in Figures 3 and 4, -
For boat fishing, a ring-shaped ferrite core 101 with a relatively low saturation magnetic flux density is coated with a metal such as amorphous 103 with a high saturation magnetic flux density on the main gap 102 part by sputtering deposition, etc., to reduce the magnetic flux in the main gap 102 part. This improves the saturation of the recording medium, enables recording and reproduction on a recording medium with high coercive force, and increases the recording density.

The MIG structure magnetic head has the characteristics that it can reduce 2% 1s0 (waveform half-width time), has low dependence on write current, and can generate a strong magnetic field compared to conventional ferrite magnetic heads.

Between the metal thin film 103 and the ferrite 101, the metal thin film 10
It is also well known that there is a reaction layer formed by the reaction between No. 3 and ferrite 101, and the reaction layer acts as a pseudo gap, which is unfavorable in terms of characteristics.

"Problem to be Solved by the Invention" In the MIG structure of a magnetic head, due to the difference in magnetic properties of the reaction layer at the interface between the low saturation magnetic flux density base material and the high saturation magnetic flux density thin film, this interface acts as a pseudo gap. the result,
A pseudo pulse is generated with respect to the reproduced signal in the main gap, causing a peak shift of the main pulse, and the recording window must be widened accordingly, which is disadvantageous to high density.

As a countermeasure for this pseudo gap, an azimuth or unevenness is added to the interface of the high saturation magnetic flux density thin film in the main gap of the magnetic head, and a reaction prevention layer is provided between the low saturation magnetic flux density base material and the high saturation magnetic flux density thin film. (Unexamined Japanese Patent Publication No. 63-53
Publication No. 706).

Furthermore, the distance between the centers of the main gap and the pseudo gap is L
Then, the center-to-center distance is set as minimum bit length<L<2X minimum bit length (Japanese Unexamined Patent Publication No. 13106/1983) to take countermeasures against pseudo gaps.

Furthermore, various methods have been reported, including changing the material of the high saturation magnetic flux density thin film to suppress the formation of a reaction layer.

[Means for Solving the Problems] Therefore, the present invention provides a magnetic head that enables high density even if a pseudo pulse occurs in the reaction layer at the interface between a low saturation magnetic flux density base material and a high saturation magnetic flux density thin film. This is what we provide.

The present invention is a magnetic head for recording and reproducing that is used in hard disk drives, VTRs, floppy disk drives, etc., in which a low saturation magnetic flux density base material such as ferrite at least in the gap at the outflow end of a slider is made of metal, amorphous magnetic material, etc. In a magnetic head formed with a high saturation magnetic flux density thin film, the pseudo gap that exists between the low saturation magnetic flux density base material and the high saturation magnetic flux density thin film is actively utilized.
In addition, the high saturation magnetic flux density thin film is made of at least three or more layers, and a non-magnetic material such as 5iOz is used to divide the layers to reduce eddy current loss at high frequencies and to form a sub-gap. Make use of it.

In other words, by superimposing the pulses generated by the pseudo gap and the sub-gap on the main pulses generated by the main gap, the peak shift in the recording frequency region where the recording density is highest and the minimum bit length is minimized, and the P Make WSO smaller.

``Embodiment'' The main gap structure of the present invention and the analog isolated waveform during reproduction are as shown in FIG.

Figure 1 shows an enlarged view of the vicinity of the main gap of the magnetic head MIG structure, showing a low saturation magnetic flux density base material 1 such as ferrite and a three-layer high saturation magnetic flux density thin film 21.2 □ such as sendust.
, 2. is provided with a non-magnetic layer 31.3□ such as SiO□ interposed therebetween, forming a main gap 4, and bonded with lead-based glass 5. The interval between the main gaps 4 is generally set to a length of 2 bits to 1 megabit.

As shown above, the isolated defined waveform has a main pulse A in the main gap 4 and a first non-magnetic layer 3 . is located and the sub-pulse A' is
The second non-magnetic layer 3□ is located 0.5 bit length away from there (2 bit length away from the main pulse A), and the sub-pulse A'' is further 0.5 bit length away from there. The interface between the third high saturation magnetic flux density thin film 2. and the ferrite 1 is located at a position 2.5 bits apart from the main pulse A, and the sub pulse A'' is set.

In addition, in a continuous waveform as shown in Figure 2, by making the main pulse A appear at the position shown in the figure, the pulses A1, B1, and C are separated by 1 bit length.
The sub-pulse A'' is separated by 1.5 bits from the main pulse A, the sub-pulse A'' is separated by 035 bits from the sub-pulse A'', and the sub-pulse A'' is separated by 0.5 bits from the sub-pulse A''. , the continuous waveform is superimposed with sub-pulses A', A'', A''.

So, Pws of pulse B. It is possible to make the output of the pulse C small and increase the output of the pulse C, thereby narrowing the pulse width and making it possible to reliably write on the recording medium.

Therefore, this leads to an improvement in the overall electromagnetic conversion characteristics, and since the high saturation magnetic flux density thin film is multilayered, it can also handle high frequencies.

Therefore, recording density can be significantly improved.

In the continuous waveform shown in Figure 2, the distance between the centers of each sub-pulse is made equal to the bit length when the 2F frequency, which is the most severe condition, is recorded on the innermost circumference of the magnetic disk. Pulse is 1 from main pulse
．． The magnetic cores are located at positions separated by 5 bits, 2 bits, and 2.5 bits.

However, if the thickness of the nonmagnetic layer is set to 200 Å or more, the magnetic resistance between the high saturation magnetic flux density thin film laminations will increase, causing a reduction in the reproduction output of the magnetic head and causing deterioration in characteristics. A desired magnetic head can be obtained by setting the thickness of the nonmagnetic layer to several tens of angstroms or less.

"Effect of the invention" The present invention has the following effects due to the above configuration.

First, the present invention reduces the peak shift of the main pulse and reduces Pw5o by superimposing the sub-pulse on the main pulse at high frequency on the inner circumferential side of the magnetic disk where the minimum bit length is the minimum bit length. This reduces the overall bit shift, enables high-frequency recording and reproduction, and greatly improves recording density.

Moreover, the present invention multilayers the metal film of the l'llG film,
Eddy current loss at high frequencies, which is unique to metal films, can be reduced, improving the S/N ratio. Note that the eddy current loss We can be expressed by the following equation.

4　ρ here, f: frequency a: radius (winding part) μ: Magnetic permeability n: number of turns ■：Current ρ: specific resistance Further, the surface thickness δ per unit volume can be expressed by the following formula.

...Low saturation magnetic flux density base material...High saturation magnetic flux density thin film...Main gear...Non-magnetic layer Note that δ is the thickness from the surface where the magnetic flux decreases to =0.368 It is. Magnetic flux leaks only from the surface, and eddy currents occur in other parts. When the membrane is multilayered,
-The membrane per layer becomes thinner, reducing the skin thickness δ and making efficient use of the membrane.

Furthermore, in the present invention, the adhesion strength can be increased by multilayering or laminating the film.

[Brief explanation of drawings]

Fig. 1 is an enlarged vertical cross-sectional structure near the main gap of the magnetic head MIG structure and an analog isolated waveform diagram during reproduction, Fig. 2 is a continuous waveform diagram of the present invention, and Figs. 3 and 4 are conventional magnetic head MIG
FIG. 3 is a longitudinal cross-sectional view of the structure.

Claims (1)

[Claims] (1) In a magnetic head in which low saturation magnetic flux density base materials are opposed to each other to form a gap, a high saturation magnetic flux density thin film is coated on one opposing surface, and a main gap is formed between the two opposing surfaces and the other opposing surface. , the high saturation magnetic flux density thin film has a laminated structure with a non-magnetic layer interposed therebetween, and the non-magnetic layer provided between the high saturation magnetic flux density thin films acts as a sub-pulse, and the sub-pulse is at least one step away from the main pulse. .5 bit length, 2 bit length,
A magnetic head characterized by being located at a distance of 2.5 bits.