JP3842509B2 - Thin film magnetic head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording / reproducing separated magnetic head, and more particularly to a thin film magnetic head that enables high-density high-frequency digital recording.
[0002]
[Prior art]
In recent years, the recording density of magnetic recording devices has been remarkably improved, and in the field of computer magnetic disk devices, the recording density has been increasing at an annual rate of 100% or more. In order to achieve a recording density of several Gb to several tens of Gb per square inch, as a magnetic head for reproduction (hereinafter referred to as “reproduction head”), a magnetic resistance and a huge regenerative power much higher than those of the conventional inductive type An MR head using a magnetoresistive element (hereinafter referred to as an MR element) has been put into practical use. On the other hand, an inductive thin film head using a conventional electromagnetic induction phenomenon is used as a magnetic head for recording (hereinafter referred to as a recording head). Actually, an MR composite thin film magnetic head in which this reproducing head and recording head are combined together is used. Hereinafter, this MR composite thin film magnetic head is referred to as a thin film magnetic head.
[0003]
FIG. 8 shows the structure of a thin film magnetic head currently used. A lower shield 2, an insulating layer 3, and a middle magnetic pole 4 are formed on the substrate 1, and an MR element 5 is formed between the lower shield 2 and the middle magnetic pole 4. Here, the middle magnetic pole 4 also has a function as a shield. A recording gap film 6 is formed on the middle magnetic pole 4, and a thin film coil 7 is further formed. An insulating layer 8 is formed to insulate the thin film coil, an upper magnetic pole (pole tip 9a, yoke 9b) is formed, and a protective layer 10 is formed on the uppermost layer to protect them. Japanese Patent Laid-Open No. 11-213331 shows that it is effective to manufacture an upper magnetic pole from two parts in a head having a recording track width of 1 micron or less. This thin film magnetic head applies a recording current to the thin film coil 7 to induce a recording magnetic flux in the upper magnetic pole 9 and the middle magnetic pole 4, and in the vicinity of the recording gap, a leakage magnetic field from the upper magnetic pole 9 and the middle magnetic pole 4 causes an air bearing. A magnetization pattern is recorded on a recording medium installed in the vicinity of the surface 11. In reproduction, a magnetic field generated from the magnetization pattern of the recording medium is detected by an MR element.
[0004]
[Problems to be solved by the invention]
In the field of magnetic disk devices, high density and high frequency are progressing. When the frequency becomes high, the change in the magnetic flux of the magnetic pole cannot follow the change in the required recording signal, and the rise time of the recording magnetic field is delayed. This delay has a problem that the recording / reproduction characteristics such as the overwrite characteristic (O / W) and the non-linear magnetization transition point shift (NLTS) deteriorate. How to make the magnetic flux change of the magnetic pole follow the required change of the recording signal is a problem to be solved by the prior art. An object of the present invention is to provide a thin film magnetic head in which this problem is suppressed.
[0005]
[Means for Solving the Problems]
The thin film magnetic head of the present invention includes a magnetoresistive element for reading between a lower shield and a middle magnetic pole, and has an upper magnetic pole facing the middle magnetic pole with a gap layer made of a nonmagnetic material interposed therebetween, The upper magnetic pole is composed of a pole tip and a yoke, the width on the gap layer side of the pole tip is a width that defines the recording track width, and the end surface of the pole tip constitutes an air bearing surface together with the end surface of the middle magnetic pole, The yoke is provided between the pole tip and the middle magnetic pole, a surface joining the yoke and the middle magnetic pole is a back contact surface, and a portion joining the middle magnetic pole is the back yoke, the air bearing A thin film coil between the middle magnetic pole and the upper magnetic pole so as to generate a magnetic flux for writing to the magnetic recording medium on the surface, The thickness of the middle pole of the portion in contact with the click, characterized in that it has the following thickness of the central pole in the vicinity of the air bearing surface.
[0006]
Next, the operation of the present invention will be described. The present invention focuses on the fact that the delay time of the magnetic flux change of the magnetic pole with respect to the change of the recording signal can be reduced by reducing the eddy current loss generated in the magnetic path of the magnetic head.
[0007]
However, with the increase in recording density of magnetic recording apparatuses, the track width is being narrowed so that the track width of the recording magnetic pole becomes 1 mm or less. If a single upper magnetic pole is formed and used, it is difficult to process the conventional structure. A method of manufacturing the top pole in two parts is advantageous. In that case, the volume of the back yoke 9c in contact with the surface S1 (hereinafter referred to as the back contact surface) where the middle magnetic pole and the yoke are in contact increases. As a result, eddy current loss increases. The magnetic recording head desirably has the same product of the cross-sectional area φ of the magnetic path other than the constricted portion at the tip of the magnetic pole near the air bearing surface. However, only the area of the back contact surface S1 is increased due to a process problem. Therefore, in view of this point, an object of the present invention is to make the magnetic flux change of the magnetic pole follow the change of the necessary recording signal without reducing the recording magnetic field strength.
[0008]
First, we examined the influence of the volume of the back yoke 9c on the recording magnetic field strength and the magnetic field rise time. It has been found that the rise time of the recording magnetic field can be reduced without decreasing the recording magnetic field strength by reducing the volume of the back yoke 9c. This is because eddy current loss can be reduced. Further, even if the volume of the side yoke 9d adjacent to the back yoke is reduced, the recording magnetic field strength is not affected. Therefore, the eddy current loss of the magnetic head is reduced without reducing the recording magnetic field, and the magnetic flux change of the magnetic pole follows the change of the necessary recording signal.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a graph illustrating an improvement in the rise of the recording magnetic field. 2 and 5 are sectional views of a thin film magnetic head of a reference example .
[0010]
Reference Example FIG. 1 shows the rising characteristics of the recording magnetic field of the thin film magnetic heads of this embodiment and the conventional example. In FIG. 2, the thin film magnetic head of this embodiment has the configuration shown in FIG. As shown in FIG. 1, the configuration of the present invention has a faster rise of the recording magnetic field than the conventional configuration. Therefore, according to this embodiment , it is possible to reduce the delay of the magnetic flux change of the magnetic pole with respect to the required change of the recording signal without reducing the recording magnetic field.
[0011]
The thin film magnetic head of FIG. 2 is opposite to the back contact surface S1 from the back contact surface S1 to the back contact surface S1 of the back yoke 9c from the distance L1 from the back contact surface S1 to the upper end surface S2 on the opposite side of the surface contacting the gap film 6 of the pole tip 9a. The distance L2 to the side surface S3 is made small. Thereby, the increase in the area of the magnetic path which increases on the back contact surface can be reduced. The order of lamination will be described. First, a lower shield 2 made of NiFe alloy, an alumina film, an MR element 5, an alumina film, and a middle magnetic pole layer 4 are laminated on an alumina titanium carbide substrate 1 covered with an insulating film. The alumina films sandwiching the MR element 5 constitute an insulating layer 3 that functions as a reproduction gap. Next, after forming the recording gap film 6 on the middle magnetic pole 4, a pole tip 9a is formed. Next, for example, an alumina film as an insulating layer is formed, and then the whole is planarized by CMP (Chemical Mechanical Polish). Thereafter, a resist insulating layer 8 that fills the gap between the thin film coils 7 and a yoke 9b were formed. The yoke 9b covers the thin film coil at the center and is joined to the middle magnetic pole 4 at the rear. This joint surface is referred to as a back contact surface S1. Next, the surface S3 of the back yoke 9c, which is a portion on the back contact surface S1 of the yoke 9b, is shaved by ion beam etching such as ion milling so that it is below the upper surface S2 of the pole tip 9a. Thereafter, a protective film 10 is coated on the pole tip 9a and the yoke 9b. Each film is formed with the above-described laminated structure while forming and patterning each film with an appropriate shape and thickness. In this laminated structure, the recording gap film and the side where the reproducing element 5 is provided are polished to form a medium facing surface (air bearing surface) 11. The middle magnetic pole is made of, for example, a NiFe alloy having a Ni concentration of 83 wt%.
[0012]
( Reference Example ) As shown in FIG. 3, most of the back yoke 9c is removed by ion beam etching such as ion milling, and the length L3 of the cross section of the surface in contact with the middle magnetic pole of the back yoke 9c is the yoke 9b. The film thickness t9b or less was formed. Thereby, the increase in the area of the magnetic path which increases on the back contact surface S1 can be reduced.
[0013]
( Reference Example ) Another head is shown in FIG. 4A is a plan view of the upper magnetic pole, and FIG. 4B is a cross-sectional view taken from 4A to 4A ′ in FIG. As shown in FIG. 4, in the other magnetic head, the area A1 surrounded by the dotted line including the back yoke 9c and the side yoke 9d was deleted, and the volume thereof was made smaller than the time when the yoke 9b was created. Further, the middle magnetic pole below the back contact surface S1 may be deleted at the same time.
[0014]
( Reference Example ) Further, as shown in FIG. 5, in another magnetic head, the back yoke 9c and the side yoke 9d are eliminated by ion beam etching such as ion milling, and the cross section of the surface in contact with the middle magnetic pole of the back yoke 9c is used. The length L3 is less than the film thickness t9b of the yoke 9b. Further, the middle magnetic pole 4b below the back contact surface S1 may be deleted at the same time, or the middle magnetic pole may be formed in advance so that there is no middle magnetic pole 4b below the back contact surface S1.
[0015]
(Embodiment 1 ) In this embodiment , as shown in FIG. 6, the film thickness t4b of the middle magnetic pole 4b below the back contact surface S1 is made thinner than the film thickness t4 of the middle magnetic pole 4 near the air bearing surface. In some cases, t4b may be set to zero.
[0016]
Any form state also, so as not to reduce the occurrence recording magnetic field intensity, reduce the cross-sectional area of the magnetic path of flow of magnetic flux, to suppress eddy currents, to reduce the delay of the magnetic poles of the magnetic flux change with respect to the change of the necessary recording signal Further, it is possible to provide a thin film magnetic head capable of realizing high-density and high-frequency recording while suppressing deterioration of recording / reproduction characteristics such as overwrite characteristics (O / W) and non-linear magnetization transition point shift (NLTS).
[0017]
(Embodiment 2 ) Next, the main part of the manufacturing process of a thin film magnetic head according to an embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a thin film magnetic head in which an upper magnetic pole is formed in the manufacturing process of FIG. An insulating film 1a made of alumina is formed on the nonmagnetic substrate 1 made of alumina titanium carbide by sputtering (2-a). A CoTaZr soft magnetic film is formed on the insulating film 1a by sputtering, and this soft magnetic film is patterned into a necessary shape, whereby the lower shield 2 is obtained. Next, an alumina insulating layer 3 and an MR element 5 are formed on the lower shield 2 (2-b). An insulating layer 3a for shortening the middle magnetic pole is produced. The middle magnetic pole 4 is formed on the insulating layer 3 so as to form the same plane as the insulating layer 3a, and then the middle magnetic pole 4 is formed on the middle magnetic pole 4 and the insulating layer 3a. Next, the recording gap film 6 is formed (2-d). Thereafter, by carrying out the subsequent steps as in Embodiment 1, to obtain a thin film magnetic head shown in the sectional view of FIG.
[0018]
In the thin film magnetic head of the present embodiment, the following can be used as the MR element. For example, a SAL bias MR element including a magnetoresistive film, a spacer, and a SAL film, a soft magnetic film bonded with an antiferromagnetic film, a spin valve MR element including a nonmagnetic metal film and a soft magnetic film, and a plurality of soft magnetic elements A GMR element having a structure in which films are stacked, a tunnel junction MR element having a structure in which an insulating film is sandwiched between two soft magnetic films, and the like. The reproducing track width of these reproducing elements is preferably set to be smaller than the width (recording track width) of the top pole tip of the thin film magnetic head.
[0019]
【The invention's effect】
As described above, according to the present invention, by reducing the volume of the back contact portion, the delay of the magnetic flux change of the magnetic pole with respect to the required change of the recording signal is reduced, and the overwrite characteristics (O / W) and non- It is possible to provide a thin film magnetic head capable of realizing high-density and high-frequency recording by suppressing deterioration of recording and reproducing characteristics such as linear magnetization transition point shift (NLTS).
[Brief description of the drawings]
FIG. 1 is a graph showing rise characteristics of a recording magnetic field according to the embodiment of FIG .
FIG. 2 is a cross-sectional view of a thin film magnetic head of a reference example .
FIG. 3 is a cross-sectional view of a thin film magnetic head of a reference example .
FIG. 4 is a cross-sectional view of a thin film magnetic head of a reference example .
FIG. 5 is a sectional view of a thin film magnetic head of a reference example .
FIG. 6 is a cross-sectional view of a thin film magnetic head according to an embodiment of the invention.
FIG. 7 is a process diagram for explaining a manufacturing method according to an embodiment of the present invention.
FIG. 8 is a cross-sectional view of a conventional thin film magnetic head.
[Explanation of symbols]
1 substrate,
1a insulating film,
2 Bottom shield,
3 Insulating layer,
4 Middle magnetic pole,
4b Middle magnetic pole in contact with the back yoke,
5 reproducing element,
6 recording gap film,
7 Thin film coil,
8 Insulating layer,
9a Pole tip,
9b York,
9c Back yoke,
9d side yoke,
10 Protective film,
11 Air bearing surface,
S1 Back contact surface,
S2 Opposite surface in contact with the gap film of the pole tip,
S3 The surface opposite the back contact surface of the back yoke,
L1 Distance between S1 and S2,
L2 Distance between S1 and S3,
L3 Length of side of back contact surface,
t4 Thickness of the middle magnetic pole in the vicinity of the air bearing surface t4b Thickness of the middle magnetic pole in contact with the back contact surface t9b Thickness of the yoke

Claims (1)

  A magnetoresistive element for reading is provided between the lower shield and the middle magnetic pole, and has an upper magnetic pole facing the middle magnetic pole across a gap layer made of a nonmagnetic material. The upper magnetic pole is a pole tip and a yoke. And the width of the pole tip on the gap layer side defines the recording track width, the end face of the pole tip constitutes an air bearing surface together with the end face of the middle magnetic pole, and the yoke and the pole tip Provided between the middle magnetic poles, the surface that joins the yoke and the middle magnetic pole is a back contact surface, and the portion that joins the middle magnetic pole of the yoke is a back yoke, and is used for writing to the magnetic recording medium on the air bearing surface In the thin film magnetic head having a thin film coil between the middle magnetic pole and the upper magnetic pole so as to generate a magnetic flux of Thin-film magnetic head, characterized in that the thickness of the central pole of the portion in contact with the following film thickness of central pole near the air bearing surface.

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