JP2501259B2 - Thin film magnetic head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic head, in which an upper insulating film for supporting an upper magnetic film is provided in a plane of the upper magnetic film, and most of the upper magnetic film is out of the plane. By not providing the structure, it is possible to provide a thin film magnetic head in which popcorn noise or noise after writing is dramatically reduced.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view of an essential part of an in-plane recording / reproducing thin-film magnetic head known from JP-A-55-84019, and FIG. 7 is a sectional view of the same part. 1 is a substrate,
2 is a lower magnetic film, 3 is a gap film made of alumina or the like,
4 is an upper magnetic film, 5 is a coil film, 6 is an insulating film made of an organic insulating resin such as novolac resin, 7 and 8 are lead-out lead portions, 9 is an insulating film, and 10 is a protective film such as alumina. .

[0003] substrate 1 has a structure obtained by depositing an insulating film 102 of Al ₂ O ₃ or the like on the ceramic structure 101, for example, Al ₂ O ₃ · TiC. The base 1 constitutes most of the slider. The base 1 as a slider has an air bearing surface by a rail (not shown) or a planar air bearing surface without a rail.

The tip portions of the magnetic films 2 and 4 are pole portions 21 facing each other with a gap film 3 made of alumina or the like interposed therebetween.
41, and the magnetic conversion operation is performed in the pole portions 21 and 41.

The coil film 5 includes two layers of coil films 51 and 52, and together with the magnetic films 2 and 4 and the gap film 3 constitutes a thin film magnetic circuit. This coil film 5 is Cu / Ti
The structure is such that the conductor film made of Cu plating is laminated on the base conductor film made of the sputtered film of
A spiral shape is formed around the coupling portion of the yoke portions of the magnetic films 2 and 4 connected to the rear of the first and the first portions 41.

The insulating film 6 is below the coil films 51 and 52 and is a lower insulating film 61 that supports the coil film 51.
And an upper insulating film 63 that covers the coil film 52 and that supports the upper magnetic film 4 above the coil film 52. The insulating film 62 is an intermediate insulating film located between the coil films 51 and 52. When the coil film 5 has a single layer structure, the intermediate insulating film 62 is omitted.

The protective film 10 is provided to protect the thin film magnetic head element composed of the magnetic films 2 and 4, the gap film 3, the coil film 5 and the interlayer insulating film 6.
It is formed as a sputtered film of alumina or the like. The perspective view of FIG. 6 shows a state before the protective film 10 is provided.

[0008]

However, in the conventional thin-film magnetic head, when a read operation is performed after a write signal is applied and a time of, for example, about 10 μs to 20 μs has elapsed, the read signal is usually Pulsed noise having a peak value significantly higher than that of the white noise of is generated. Fig. 8 is an oscilloscope waveform diagram showing pulse noise in white noise, with 0.5 µ per unit scale on the horizontal axis.
Take the time scale represented by s, and the vertical axis is 30 per unit scale
The voltage scale is expressed in μV. Below the waveform diagram, a time chart of the write operation and the read operation is displayed along the time axis. When the read operation is started at t0 after the write operation is stopped, the time of t0 is used as a reference.
When 5 μs to 2.5 μs has passed, pulse-like noise PP having a peak value significantly higher than the level of the white noise PW is generated. Such noise PP is called popcorn noise, access noise or post-write noise by those skilled in the art.

The generation mechanism of the popcorn noise PP is not always clear, but it is presumed that the main cause is the delay in the formation of the magnetic domains in the magnetic films 2 and 4 when the write operation state shifts to the stationary state. The magnetic films 2 and 4 have magnetic anisotropy, and the magnetic domains facing the hard axis direction HH as shown in FIG. 9 at the time of writing operation are as shown in FIG. 10 in the static state. Then, the direction is changed from the hard axis direction HH to the easy axis direction HE rotated by 90 degrees. The popcorn noise PP is generated due to a time delay when the magnetic domains of the magnetic films 2 and 4 rotate from the hard axis direction HH to the easy axis direction HE.

The popcorn noise PP has a peak value V0-
When p is large, it reaches 100 .mu.V0-p and cannot be distinguished from a normal read signal, resulting in a read error in the magnetic disk drive. This is a very important problem that may deny the practicality of the thin film magnetic head. However, at present, there is no effective solution. For example, it is conceivable to increase the time (post.write.recovery.time) from the write operation to the read operation, but in applying this, it is essential to change the system of the magnetic disk drive device. And, in reality, it's almost impossible. And post. Light. recovery. Taking a long time runs counter to the demand for high-density recording.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to provide a thin film magnetic head capable of dramatically reducing popcorn noise.

[0012]

In order to solve the above-mentioned problems, a thin film magnetic head according to the present invention is formed on a substrate with a lower magnetic film, a coil film embedded in an insulating film, and the insulating film. A thin film magnetic head in which upper magnetic films are sequentially stacked, the insulating film includes an upper insulating film that supports the upper magnetic film, and the upper insulating film is provided in a plane of the upper magnetic film. The upper magnetic film and the upper magnetic film are not provided on most of the surface outside the upper magnetic film.
The coil film positioned outside the upper magnetic film is a ceramic film.
It is characterized in that it is covered with a protective film containing ku as a main component .

[0013]

It has been found that if the upper insulating film is provided in the surface of the upper magnetic film and is not provided in the most part outside the surface of the upper magnetic film, popcorn noise is significantly reduced. Although the reason is not clear, it is presumed that there is no upper insulating film outside the surface of the upper magnetic film, so that the stress due to curing shrinkage of the upper magnetic film will not be applied from outside the upper magnetic film. To be done. The coil film located outside the upper magnetic film is covered with a protective film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a fragmentary plan sectional view of a main part of a thin film magnetic head according to the present invention, and FIG.
In the figure, the same reference numerals as those in FIGS. 6 to 7 denote the same components. The insulating film 6 is located below the coil film 5 and supports the coil film 51.
And an upper insulating film 63 that supports the upper magnetic film 4. Since the embodiment shows an example having two layers of coil films 51 and 52, an intermediate insulating film 62 is provided between the lower insulating film 61 and the upper insulating film 63.

The upper insulating film 63 is provided on the surface of the upper magnetic film 4, but is not provided on most of the surface of the upper magnetic film 4. The coil film 52 located outside the upper magnetic film 4 is covered with the protective film 10. In the insulating film structure as described above, after the upper insulating film 63 is formed inside and outside the region where the upper magnetic film 4 is formed, the upper insulating film 63 in the region where the upper magnetic film 4 is to be formed is left and the rest is left. It can be formed by removing it by means such as ion milling, or by matching the mask pattern when forming the upper insulating film 63 with a required pattern. In the embodiment, the two-layer structure of the coil films 51 and 52 is shown, but the number of layers of the coil film is arbitrary. The structure may be a single layer or a structure having three or more layers of coil films. In any case, the upper insulating film supporting the upper magnetic film 4 has an insulating film structure in which the upper insulating film is in the surface of the upper magnetic film 4 but is not present in most of the outside of the surface.

FIG. 3 shows popcorn noise between the thin film magnetic head according to the present invention shown in FIGS. 1 and 2 (invention product) and the conventional thin film magnetic head shown in FIGS. 6 and 7 (conventional product). It is a figure which graphs and shows a number. As shown in the figure, the popcorn noise, which was around 130 in the conventional product, is dramatically reduced to 0 to several in the product of the present invention. Next, the conditions set to obtain the data of FIG. 3 will be described.

FIG. 4 is a time chart of write and read operations for obtaining the data of FIG. The write operation was performed with a write current of 40 mA0-p and a write time of 1 ms. After completion of the writing operation, post for 10 μs. Light. recovery. Time was taken and the read operation was performed. The read time is 16 ms. A test for 2 minutes was performed with the above as one cycle. Assuming that the white noise level is 30μV0-p, the noise threshold voltage for popcorn noise detection is 40μV0-p.
The test was conducted by setting p and 50 μV 0-p respectively.

FIG. 5 is a block diagram of the measurement circuit provided to obtain the data of FIG. In the figure, 12 is a thin film magnetic head, 13 and 14 are amplifiers, 15 is a filter, 1
6 is an operational amplifier, 17 is a comparator, 18 is a logic gate, 1
9 is a read / write switching controller, 20 is a gate controller, 2
1 is a gate. A timer, 22 is a logic gate, and 23 is a popcorn counter.

A switching signal supplied from the switching controller 19 to the amplifier 13 switches between reading and writing according to the time chart shown in FIG. In the read operation, the signals output from the thin film magnetic head 12 are transmitted to the amplifiers 13 and 14
Amplified by, the necessary frequency component is extracted by the filter 15, and input to the comparator 17 through the operational amplifier 16. The comparator 17 compares the signal supplied from the operational amplifier 16 with a noise threshold for popcorn noise detection set by the Zener diode 24, and produces an output of logic 1 when the former is larger than the latter. . The comparison output of the logic 1 is passed through the logic gate 18 and popcorn noise. It is given to the counter 23 to count. Popcorn noise. The counting timing in the counter 23 is determined by the gate controller 20 and the gate timer 21 from the logic gate 2
2 through the timing signal provided.

[0020]

As described above, in the thin film magnetic head according to the present invention, the upper insulating film for supporting the upper magnetic film is provided in the surface of the upper magnetic film, and the upper insulating film is provided outside the surface of the upper magnetic film. Since most of them are not provided, it is possible to provide a thin film magnetic head with significantly reduced popcorn noise.

[Brief description of drawings]

FIG. 1 is a partial plan sectional view of a main part of a thin film magnetic head according to the present invention.

FIG. 2 is a sectional view of a main part of a thin film magnetic head according to the present invention.

FIG. 3 is a thin-film magnetic head according to the present invention (present invention product).
FIG. 6 is a graph showing the number of popcorn noises of a conventional thin film magnetic head (conventional product).

FIG. 4 is a time chart of write and read operations for obtaining the data of FIG.

5 is a block diagram of a measurement circuit provided to obtain the data of FIG.

FIG. 6 is a perspective view of a main part of a conventional thin film magnetic head.

FIG. 7 is a sectional view of a main part of a conventional thin film magnetic head.

FIG. 8 is an oscilloscope waveform diagram showing pulsed noise in white noise.

FIG. 9 is a diagram showing a model of a magnetic domain structure during a write operation.

FIG. 10 is a diagram showing a model of a magnetic domain structure during a read operation.

[Explanation of symbols]

 1 Base 2 Lower Magnetic Film 4 Upper Magnetic Film 51, 52 Coil Film 61 Lower Insulating Film 63 Upper Insulating Film

Claims (1)

(57) [Claims] 1. A lower magnetic film and an insulating film embedded on a substrate.
Coil film and upper magnetic film formed on the insulating film
A thin film magnetic head in which the insulating film is an upper insulating film supporting the upper magnetic film.
And the upper insulating film is provided in a plane of the upper magnetic film.
And is provided on most of the surface of the upper magnetic film.Oh
Without Before being located outside the upper magnetic film and the upper magnetic film
The coil film is made of a ceramic-based protective film.
Covered A thin film magnetic head characterized in that