JPS6339111A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To contrive to improve both the line recording density and the track density by using a material having a larger saturated magnization and a lower permeability toward the 2nd magnetic film remote from a nonmagnetic layer more than the 1st magnetic film and making the width wider. CONSTITUTION:Since the magnetic field strength generated by a coil layer 15 at write is very large, the write magnetic field at write is decided by the saturated magnetization MS2 of magnetic layers 22, 32 according to the magnetization curve C2. Since the magnetic field is nearly 1/3 of the write magnetic field, only magnetic layers 21, 31 at the inner side having a large permeability are effective. Thus, the recording density characteristic at read depends on the length (g) of the recording/reproducing gap 16, the thickness pt1 of the magnetic layer 31 and the thickness pb1 of the magnetic layer 21. The write magnetic field Hs depends on the size g+pt+pb, but since the recording density D50 depends on the size g+pt1+pb1, both the magnetic field Hw and the recording density D50 are increased. Thus, the high line recording density is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic head for reading and writing signals on a magnetic recording medium, and particularly to a thin film magnetic head with high reproduction resolution.

[Conventional technology]

2. Description of the Related Art As the density and capacity of magnetic recording devices increase and the transfer speed of recorded information increases, thin film heads have been put into practical use in place of bulk heads. Thin-film heads are characterized by the sharp shape of the magnetic field that is generated, which allows the bit density in the recording track direction, that is, the linear recording density, to be oriented.The thin-film head also uses photolithography technology to process narrow track widths with high precision. This is because track density can be improved.

The surface of a conventional thin film head facing a magnetic recording medium has a structure in which two magnetic pole pieces 20 and 30 are disposed above and below a recording/reproducing cap 16, as shown in FIG.

[Problem that the invention seeks to solve]

In the conventional thin film head described above, the linear recording density is closely related to the thickness pb of the lower pole piece 20, the thickness pt of the upper pole piece 30, and the length g of the recording/reproducing gap 16. That is, in order to improve the linear recording density, it is necessary to reduce these dimensions. However, these dimensions also affect the write field, and as these dimensions decrease, the field strength tends to decrease as well.

The above relationship is based on the recording density D 50 (bi
ts/ms> and the write magnetic field Hw (A/m>), it can be graphed as shown in FIG.

It can be seen from FIG. 5 that there is naturally an upper limit to the linear recording density due to restrictions on the write magnetic field. To write on a magnetic recording medium, a write magnetic field Hw of at least 60×10]A/'m is required, so the recording density D50 is 700
bits/is, which was the upper limit of the linear recording density of conventional thin film heads.

On the other hand, in order to improve the track density, it is necessary to narrow the width of the recording/reproducing gap 16 (i.e., track width) Tw in FIG. It is important to take into consideration the characteristics related to track positioning errors (hereinafter referred to as off-track) that occur during this process. The characteristics related to off-track include an off-track cross 1-hake characteristic and an off-track override characteristic. off track cross 1
The magnetic head approaches the adjacent track by off-track, and the information recorded there becomes noise and enters the magnetic head. The off-track override characteristic refers to the fact that when new information is written over old information, off-track occurs and the remaining old information acts as noise.

When the off) rack is ε and the track pitch is Tp, the S/N of the −F noise is as shown in FIG. 6 for T w /T p. That is, as the track width Tw becomes smaller, the S/N of off-track crosstalk improves, but the S/N of off-track override deteriorates. These characteristics also change depending on the relationship between off-track ε and I~rack pitch Tp, and the allowable S/N is 20 dB.
Given the above, an optimal track width Tw exists when Tr) -1,0ε, but no optimal Tw exists when Tp=5ε9, that is, the upper limit of the track density is determined by off-track ε. Despite various improvements, it is impossible to reduce the off-track ε to about 2 μm or less, and for this reason, with conventional thin film RAD, it is only 20 μm! A track pitch of less than n was not possible.

In other words, the track density of the conventional thin film head is 50
jracks/Ilm was the upper limit.

An object of the present invention is to provide a thin film magnetic head that can achieve high linear recording density and high track density that exceed the recording density limits of the conventional thin film heads mentioned above.

[Means for solving problems]

The thin film magnetic head of the present invention is a thin film magnetic head in which a pair of magnetic poles having a soft magnetic film are arranged on a substrate with a nonmagnetic layer forming a gap and a conductor layer forming a coil sandwiched between the pair of magnetic poles. A first soft magnetic film close to the non-magnetic layer and having high magnetic permeability on at least one side, and a surface facing the recording medium that is farther from the non-magnetic layer than the first soft magnetic film and has high saturation magnetization and low magnetic permeability. and a second soft magnetic film having a wide width in a direction parallel to the nonmagnetic layer.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings.

Referring to FIG. 1, one embodiment of the present invention includes a substrate 11;
an insulating layer 18, a lower magnetic pole 20, an upper magnetic pole ff130,
It is composed of a coil 15 and a recording/reproducing gap 16.

The lower magnetic pole 20 and the upper magnetic pole 30 formed on the substrate 11 have a minute gap that becomes the recording/reproducing gap 16 at the end facing the recording medium (not shown), and a small gap on the side opposite to the recording/reproducing gap 16. They are arranged side by side so that they touch each other at their ends. A coil layer 15 made of a conductor is formed between the lower magnetic pole 20 and the upper magnetic pole 30 with an insulating layer 18 interposed therebetween. Further, the bottom magnetic pole 20 is made up of two magnetic layers 21 and 22, and the top magnetic pole 30 is also made up of two magnetic layers 31 and 32. In this embodiment, as described above, the upper and lower outer magnetic poles 2
0.30 is a laminate consisting of two magnetic layers.

FIG. 2 is a plan view of the tips of the magnetic poles 20 and 30 shown in FIG. 1, viewed from the surface facing the recording medium. The first in this example
The feature is that among the two magnetic layers of the upper and lower magnetic poles 20.30,
Magnetic layers 21 and 31 closer to the recording/reproducing gap 16
The magnetic permeability of the magnetic layers 22 and 32 further away from the recording/reproducing gap is increased, and the saturation magnetization is increased and the magnetic permeability is decreased. In this example, the magnetic layers 21 and 31 are made of Ni-Fe with a saturation magnetization of 0.85 T (Tesla) and a relative permeability of 3000, and the magnetic layers 22 and 32 are made of Co with a saturation magnetization of 1.3 T and a relative permeability of 1000. -Zr-
Nb was used.

The magnetization curve (magnetization M with respect to the write magnetic field H) of the thin film magnetic head of this embodiment is as shown in FIG. That is, the magnetic layers 21 and 31 near the recording/reproducing gap 16 have a magnetization curve C1, and the magnetic layers 22 and 32 far from the recording/reproducing gap 16 have a magnetization curve C2. The principle of improving the linear density of the thin film head of this example is shown below.

First, since the magnetic field intensity generated by the coil layer 15 during writing is very large, the magnetization curve C shown in FIG.
2, the write field is determined by the saturation magnetization MS2 of the magnetic layers 22 and 32. On the other hand, since the read magnetic field is about 1/3 of the write magnetic field, only the inner magnetic layers 21 and 31 with high magnetic permeability act. Therefore, the recording density characteristics of the present thin film head during reading are determined by the length g of the recording/reproducing gap 16, the thickness r)L+ of the magnetic layer 31, and the thickness pbl of the magnetic layer 21.

Referring to FIG. 5, in the thin film head of this embodiment, the write magnetic field Hw is determined by g0pt+pb,
Recording density. is g+pt, +pbl(<g+pt t
+p b ), it is possible to have high values for the magnetic field Hw and the recording density D50 at the same time, and it is possible to achieve a higher linear recording density than the conventional thin film head.

The second feature of this embodiment is that the width W of the magnetic layers 22 and 32 far from the recording/reproducing gap 16 in FIG.
The reason is that w is made wider than the width Tw of the recording/reproducing gap 16. As mentioned above, during writing, the magnetic layers 22 and 32
acts, and the magnetic layers 21 and 31 act at the time of reading, so the above configuration allows for so-called wide write, narrow gap (WIDE WRITE, NA)
RROW READ>, and therefore the off-track characteristics can be improved.

FIG. 7 shows off-track crosstalk and off-track override characteristics when Tp=5ε in the thin film magnetic head of this embodiment. In addition, in FIG. 7, W w
It was set as = T w + ε.

From FIG. 7, it can be seen that an optimum track width Tw exists for a track pitch Tp that is five times off-track 1ε. Therefore, the thin film head of the present invention can achieve higher track density than conventional thin film heads.

As described above, the thin film magnetic head of this embodiment can increase both the linear recording density and the track density.

In this embodiment, a thin film head in which the upper and lower magnetic poles each consist of two magnetic layers has been described, but the present invention can also be applied to a thin film head in which the upper and lower magnetic poles are composed of three or more magnetic layers, and the same effect can be obtained. Furthermore, the present invention can be similarly applied to a thin film head in which an intermediate layer is provided between each magnetic layer in order to improve high frequency characteristics. Furthermore, the present invention is also effective when applied to either the upper or lower magnetic pole. Therefore, any of the above thin film heads does not depart from the present invention.

〔Effect of the invention〕

As explained above, the present invention provides a thin film magnetic head in which a pair of magnetic poles each having a non-magnetic film are arranged with a non-magnetic layer forming a gap and a conductor layer forming a coil in between. By making the second magnetically difficult film far from the nonmagnetic layer a material with large saturation magnetization and low magnetic permeability, and widening the width, it is possible to improve both linear recording density and track density. .

Easy drawing,! 11. Explanation: FIG. 1 is a cross-sectional perspective view showing a thin film magnetic head according to an embodiment of the present invention, FIG. 2 is a plan view of the tip of the magnetic pole 20, 30 shown in FIG. 1, viewed from the surface facing the recording medium. FIG. 3 is a graph showing the magnetization curves of the magnetic layers 21, 22, 31, and 32 shown in FIG. The figure is a graph showing the recording density and write magnetic field strength of a thin film magnetic head, Figure 6 is a graph showing off-track characteristics of a conventional thin film magnetic head, and Figure 7 is an off-track graph of the thin film head of the embodiment shown in Figure 1. It is a graph showing an example of characteristics.

DESCRIPTION OF SYMBOLS 11... Substrate, 15... Coil layer, 16... Recording/reproducing gap, 18... Insulating layer, 20... Lower magnetic pole, 21.22... Magnetic layer, 30... Upper magnetic pole , 31
．． 32...Magnetic layer.

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Half 2 drawings Village 3 map Hou 4wJ Volume 5 Diagram g+ptsuPb　(HML)

Claims (1)

[Claims] In a thin film magnetic head in which a pair of magnetic poles having a soft magnetic film are arranged on a substrate with a nonmagnetic layer forming a gap and a conductor layer forming a coil in between, the nonmagnetic layer is disposed on at least one of the pair of magnetic poles. A first soft magnetic film having a high magnetic permeability close to the first soft magnetic film, and a first soft magnetic film having a large saturation magnetization and a low magnetic permeability which is further away from the nonmagnetic layer than the first soft magnetic film and parallel to the nonmagnetic layer on the surface facing the recording medium. A thin film magnetic head comprising: a second soft magnetic film having a wide width in a direction;