JPH1116223A - Magnetic head structure - Google Patents

Abstract

(57) [Problem] To provide a magnetic head structure that is low-cost and easy to manufacture. SOLUTION: A disk facing surface of a resin slider portion 2a which contacts a magneto-optical disk is formed in a spherical surface 2b, and a magnetic core and a coil are provided in the slider portion 2a. The slider portion 2a is pressed against the magneto-optical disk by a leaf spring. The spherical surface 2b protrudes toward the magneto-optical disk from the magnetic pole 7b, and the magnetic pole 7b is arranged at a predetermined distance from the vertex O of the spherical surface in a direction away from the leaf spring in the outer circumferential direction of the magneto-optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding type magnetic head structure. More specifically, the present invention relates to an external storage device of a computer, and a magnetic recording device and a magnetic head structure of a magneto-optical recording and reproducing device used for a recording and reproducing device of music and video signals and other information.

[0002]

2. Description of the Related Art Conventionally, magnetic recording of a magnetic head sliding type has been mainly performed by a magnetic tape or a flexible disk. In recent years, a mini disk (hereinafter referred to as MD) has been widely used for music for magneto-optical recording. is there. The MD presupposes the use of a sliding magnetic head so that overwriting of magneto-optical magnetic field modulation can be realized with a simple magnetic head structure, and the medium has a sliding film for sliding.

Conventionally, a sliding magnetic head structure for magneto-optical recording, particularly for MD, has been disclosed in Japanese Patent Application Laid-Open No. 6-195851. This entire structure is shown in FIG.

In FIG. 10, reference numeral 101 denotes a slider means on which a magnetic core 102 is mounted. The details of the slider means 101 are disclosed in JP-A-7-129902, which is shown in FIG. On the medium facing surface of the slider means 101, a cylindrical surface 101a is formed as a sliding surface. 102
a is a magnetic pole exposed on the medium side of the magnetic core 102.

[0005] Slider means 101 including a cylindrical surface 101a
Uses a resin material having excellent wear resistance and lubricity for the medium facing surface, and has an effect of preventing abrasion damage of the slider and the medium.

The cylindrical surface 101a comes into contact with the sliding film of the MD by the pressing force of the spring portion 104 serving as the loading means, so that the magnetic pole 102a comes close to the recording film. The magnetic pole 10 is applied to the recording film heated by the converged laser light.
Thermomagnetic recording is performed by applying a modulation magnetic field from 2a.

[0007]

However, the above-mentioned conventional magnetic head has the following problems. That is, since the sliding surface is constituted by a cylindrical surface, the cylindrical surface 10
1a needs to be in line contact with the sliding film of the MD. In order to follow the runout of the sliding film, a complicated mechanism such as a gimbal 103 for giving a degree of freedom to the inclination is required.
Because it requires precision forming, it becomes very expensive,
This has been a factor in increasing the cost of the magnetic head structure.

Also, in order to press the cylindrical surface 101a against the sliding film, the spring portion 104 needs to generate a pressing force enough to deform the gimbal 103. That is, a large pressing force is required, and the frictional force between the sliding film and the sliding film is increased, thereby causing a damage to the MD.

It is desirable from the viewpoint of efficiency that the magnetic pole 102a is as close as possible to the recording film in terms of efficiency. However, as shown in FIG. 11, the actually sliding cylindrical surface 101a and the magnetic pole 102a are considerably separated from each other. If there is, the followability is deteriorated, and the efficiency is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-efficiency magnetic head structure which is easy to manufacture at a low cost in consideration of the above problems of the conventional magnetic head structure.

[0011]

According to a first aspect of the present invention, there is provided a magnetic head structure used for a disk-shaped recording medium having a sliding surface. A magnetic field generating means having a magnetic pole for applying a magnetic field to the recording medium, a slider means attached to the magnetic field generating means and having a protrusion protruding from the magnetic pole toward the recording medium, and the slider means A load means for applying a pressing force to the slider means in a direction substantially perpendicular to the sliding surface, and pressing the projection against the sliding surface. The loading means is arranged to extend in series in a tangential direction of the recording medium, and the magnetic poles are offset from a vertex of the protrusion in a radial direction and a tangential direction of the recording medium. A magnetic head structure according to claim.

According to a second aspect of the present invention, in the first aspect, the magnetic pole is offset with respect to an apex of the protrusion at an outer peripheral side of the recording medium and at a side farther from the loading means. It is a magnetic head structure of the description.

According to a third aspect of the present invention, the center of the magnetic pole is positioned about 1.
2 mm or less, about 0.2 mm farther from the loading means
The magnetic head structure according to claim 2, wherein the magnetic head structure is offset.

According to a fourth aspect of the present invention, the magnetic pole is offset from an apex of the protrusion on an inner peripheral side of the recording medium and on a side closer to the loading means. 3. The magnetic head structure according to item 1.

According to a fifth aspect of the present invention, there is provided the magnetic head structure according to any one of the first to fourth aspects, wherein a peripheral portion of a vertex of the protrusion is a spherical surface.

According to a sixth aspect of the present invention, the periphery of the apex of the protrusion is an elliptical surface.
A magnetic head structure according to any one of the above.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
Perspective view showing a magnetic head structure according to the embodiment of the present invention,
2 is a plan view of FIG. 1, FIG. 3 is a sectional view of a main part of FIG. 1, FIG. 4 is a bottom view of the main part of FIG. 1, and FIG. 5 is a slider of the magnetic head structure according to the first embodiment of the present invention. FIG. 6 is a calculation diagram for designing the unit, and FIG. 6 is an explanatory diagram of the operation of the magnetic head structure according to the first embodiment of the present invention. In each figure, the right-handed rectangular coordinate system is defined as shown. In the following, for convenience, the positive and negative sides of the x axis are called front and rear, respectively, the positive and negative sides of the y axis are called left and right sides, and the positive and negative sides of the z axis are upper and lower sides. Shall be called.

In this embodiment, a magneto-optical disk 1 is used as a recording medium having a sliding surface. As shown in FIG. 6, for example, the magneto-optical disk 1 includes a plurality of layers, that is, a transparent substrate 1a made of polycarbonate or the like, a recording layer 1b made of a perpendicular magnetization easy film, a protective layer 1c made of resin or the like, and a slider sliding frictional force reduced. To provide a sliding film 1d. The magneto-optical disk 1 is provided with a large number of concentric recording tracks or a spiral recording track centered on a rotation center (not shown).

As shown in FIG. 2, in this embodiment, the main axis of the magnetic head structure is parallel to the x-axis. On the other hand, a track (not shown) of the magneto-optical disk 1 is also parallel to the x-axis at a point (contact point) where the magnetic head structure and the magneto-optical disk 1 come into contact. An arrangement in which the tangential velocity direction (referred to as “sliding direction”) at the contact point of the rotating magneto-optical disk coincides with the main axis direction of the magnetic head structure is generally referred to as an in-line arrangement. In the present embodiment, the magneto-optical disk 1 rotates in the direction of arrow ω in FIG. 2, and the magnetic head structure seeks with the optical head (not shown) in the direction of arrow R, which is the radial direction of the magneto-optical disk 1. Perform the operation.

As shown in FIGS. 1 and 2, the magnetic head structure according to the present embodiment includes a slider structure 2 and a fixing plate 4 molded from resin. Slider structure 2
Are connected to a fixed plate 4 via a leaf spring 3 formed of a conductive metal. The leaf spring 3 functions as a load unit that presses the slider structure 2 in a direction substantially perpendicular to the sliding surface 1 d of the magneto-optical disk 1.

The magnetic head structure is fixed to an optical head (not shown) for irradiating a laser beam by a fixing plate 4, and moves in the direction of arrow R together with the optical head.

A slider portion 2a is provided at an end of the slider structure 2 in the positive direction of the x-axis. The slider portion 2a has a magnetic core 7 made of ferrite or the like and a coil 8 wound around the magnetic core 7. Is installed.

Since the leaf spring 3 is sufficiently wide in the y-axis direction and sufficiently thin in the z-axis direction, it can be deformed only by a moment about the y-axis. Therefore, the leaf spring 3 gives the slider portion 2a a degree of freedom substantially only in the z-axis direction.

The leaf spring 3 is integrated with the slider structure 2 and the fixed plate 4 by insert molding. The leaf spring 3 also has a function of supplying power to the coil 8. An end in the x-axis direction is connected to the coil 7, and the other end is exposed as a terminal 5. That is, when the terminal 5 is energized, a current flows through the coil 8.

As the material of the slider structure 2 and the fixing plate 4, it is preferable to use a liquid crystal polymer having slidability in view of mechanical strength, accuracy, shape stability and the like.

As a material of the leaf spring 3 as a conductor,
It is preferably made of a metal having a low resistance value, such as phosphor bronze or beryllium copper. These are desirably plated with nickel or the like in order to improve corrosion resistance. In addition, when electric resistance does not matter, a stainless steel material or the like can be used.

As shown in FIGS. 3 and 4, the slider portion 2a
On the side facing the magneto-optical disk 1, a spherical surface (radius: 10 mm) 2b is provided as a protruding portion. The slider structure 2 is formed of resin, and the slider portion 2
a, the spherical surface 2b is integrally formed from resin.

The magnetic core 7 is a so-called E-shaped core and has a center yoke 7c and two side yokes 7a. A coil 8 is wound around the center yoke 7c.
The end face of the center yoke 7c facing the magneto-optical disk 1 is exposed as a magnetic pole 7b from the slider section 2a.

Next, a preferred arrangement of the magnetic pole 7b in the slider portion 2a will be described. The arrangement of the magnetic pole 7b is designed in consideration of the possibility that the position of the sliding film 1d of the magneto-optical disk 1 is displaced according to the rotation ω. Since the magnetic pole 7b is very hard as compared with the sliding film 1d, there is a possibility that the sliding film 1d may be damaged if they contact each other during operation. Therefore, it is necessary to dispose the magnetic pole 7b so that the sliding film 1d does not contact.

First, the details of the structure of the bottom of the slider portion 2a will be described with reference to FIGS. The vertex O of the spherical surface 2b is
As shown in FIG. 3, it protrudes downward from the surface S1 where the magnetic pole 7b exists. In the present embodiment, the protrusion amount is 50 μm. Here, the surface S1 is a magnetic pole 7b of a virtual plane parallel to the xy plane and extending infinitely in the xy direction.
Is a plane including.

FIG. 5 shows the arrangement of the magnetic poles 7b and the slider portion 2a.
FIG. 5 is a diagram showing the design concept of FIG. 5, viewed from below the slider portion 2a, that is, a diagram corresponding to FIG. FIG. 5 shows an xy plane whose origin is the vertex O of the spherical surface. The coordinate axes in FIG. 5 correspond to the coordinate axes in other drawings. The curves and the like obtained by the simulation are displayed on the xy plane in FIG.

According to the present embodiment, the spherical surface 2b of the slider portion 2a contacts the sliding film 1d of the magneto-optical disk 1 at a small point. Since the sliding film 1d has some elasticity,
The contact portion between the spherical surface 2b and the sliding film 1d has a finite size. Assuming that the pressing force is approximately 6 to 10 mN, the size of the contact portion in this embodiment is approximately 0.05 to 0.5 mm in diameter.
It is about 1 mm.

When the spherical surface 2b is in contact with the sliding film 1d at the origin O in FIG. 5, the surface S1 and the sliding film 1d are parallel to each other. This state is referred to as “standard operating state” in the specification of the present application. However, as a result of the magneto-optical disk 1 being inclined with respect to the slider structure, when the spherical surface 2b and the sliding film 1d come into contact with each other at a point different from the origin O in FIG.
Intersect with the sliding film 1d because they are not parallel, and an intersection line is formed on the virtual plane S1. When the tilt angle between the magneto-optical disc 1 and the surface S1 changes with the rotation of the magneto-optical disc 1, the point of projection of the contact point between the spherical surface 2b and the sliding film 1d on the xy plane becomes the origin on the xy plane. Move the position shifted from O. At this time, the surface S1 is the sliding film 1 of the magneto-optical disk 1.
The part (intersection line) intersecting with d also moves on the surface S1.

In FIG. 5, a region R1 indicates a point at which the sliding film 1d of the rotating magneto-optical disk 1 contacts the spherical surface 2b.
The area formed by the projection on the y-plane is shown. In an ideal state, the region R1 is a lot corresponding to the point O in FIG. However, due to various surface deflections and inclinations of the magneto-optical disk 1 due to rotation, mounting errors of the magnetic head structure, and the like, the region R1 has a unique shape and spread shown in FIG. When the contact point between the sliding film 1d and the spherical surface 2b moves in the region R1, the intersection line between the surface S1 and the sliding film 1d moves largely on the surface S1. A curve C1 is obtained by projecting an inner envelope of a virtual intersection line group where the sliding film 1d intersects with the surface S1 on the xy plane. While the magneto-optical disk 1 rotates, the intersection line between the sliding film 1d and the surface S1 never penetrates inside the curve C1. The area outside the curve C1 is called an area R2. The curve SP is
The intersection line between the spherical surface 2b and the surface S1 is shown projected on the xy plane.

Since the region R1 is a region where the spherical surface 2b is in contact with the sliding film 1d, the magnetic pole 7b cannot be arranged in the region R1. Under the premise that the magnetic pole 7b is placed on the surface S1, the magnetic pole 7b
Is arranged, the magnetic pole 7b comes into contact with the sliding surface 1d of the magneto-optical disk 1. Therefore, the magnetic pole 7b is located in the region R1.
It should be located outside and inside region R2. FIG. 5 shows an example of a possible arrangement of the magnetic poles 7b.

In this embodiment, as shown in FIG. 5, a region offset from the origin O substantially along the y-axis,
In other words, a region offset along the radial direction of the magneto-optical disk 1 toward the inner circumference or the outer circumference of the magneto-optical disk 1 may include the magnetic pole 7b with the greatest margin. Therefore, the magnetic pole 7
b can be arranged at two types of positions on the inner peripheral side or the outer peripheral side of the magneto-optical disc 1 with respect to the vertex O of the spherical surface 2b. However, when the magneto-optical disk 1 is an MD, since the recording area exists near the outermost periphery of the disk, it is necessary to locate the magnetic pole 7b at the outermost periphery of the disk. In that case, compared to the magnetic pole 7b, the spherical surface 2b
Must be arranged on the inner peripheral side. In other words, the magnetic pole 7
As shown in FIG. 5, b needs to be arranged on the outer peripheral side of the magneto-optical disk 1 (a region where the y coordinate is positive).

Further, since the region R2 is not subject to the y-axis because of the behavior of both the leaf spring 3 and the magneto-optical disk 1,
As shown in FIG. 5, the magnetic pole 7 is offset in the positive direction along the x-axis, that is, farther away from the leaf spring 3 by ε.
The distance between b and the region R2 further increases. Considering the possibility of contact between the sliding film 1d and the magnetic pole 7b, this setting is extremely effective because the larger the distance, the better.

In general, it is desirable that the length of the magnetic pole 7b in the y-axis direction is sufficiently large so as to cover the tracking range of the objective lens actuator. Therefore, a sufficiently large magnetic pole can be used by offsetting the magnetic pole 7b from the spherical center O by ε. In this simulation, it is optimal that ε is about 0.1 mm to 0.2 mm.

It is preferable that the magnetic pole 7b is arranged near the origin O which is a standard contact point. The reason is that the shorter the distance between the magnetic pole 7b and the origin O, the smaller the fluctuation of the distance (distance in the z-axis direction) between the magnetic pole 7b and the recording layer 1b, which occurs when the magneto-optical disk 1 is tilted. This is because it is possible to perform a proper recording. Therefore, in the configuration of the present embodiment, the position shown in FIG. 5 is a substantially optimum position where the magnetic pole 7b is arranged. According to the simulation based on this arrangement, the distance δ between the center of the magnetic pole and the origin O in the y-axis direction is about 1.2 mm at the maximum, and the fluctuation range of the distance between the magnetic pole 7b and the recording layer 1b at this time is ± 0.5 50 μm
It turned out that it can be suppressed to the extent.

As described above, in the present invention in which the slider structure 2 is brought into contact with the sliding surface 1d of the magneto-optical disk 1 with its spherical surface 2b, the above design method using the graph of FIG. Was confirmed.

Next, the operation of this embodiment will be described.

When the magnetic head structure descends onto the magneto-optical disk 1, it comes into contact with the magneto-optical disk 1 in the form shown in FIG. As shown in FIG. 6, the slider portion 2a comes into contact with the sliding film 1d on the spherical surface 2b, and the magneto-optical disk 1 moves in the ω direction of FIG.

When a current flows from the terminal 5 to the coil 8 via the leaf spring 3, a magnetic flux φ is applied to the magnetic core 7 made of ferrite.
Occurs. Assuming that a current flows so that the negative direction of the z-axis becomes the N pole, a magnetic flux φ is generated between the magnetic pole 7b and the side yoke 7a as shown in FIG. In the vicinity of the magnetic pole 7b, a sufficient number of magnetic fluxes φ for recording pass through the recording layer 1b.

In this state, when a laser beam converged from an optical head (not shown) is applied to the recording layer 1b immediately below the magnetic pole 7b and modulated by information for recording the current of the coil 8, the information pattern is directed to the recording layer 1b. Is recorded as

Although the slider portion 2a has only a degree of freedom in the z-axis direction, even when the magneto-optical disk 1 is tilted, a stable contact state can always be maintained on the magneto-optical disk 1 with the spherical surface 2b. As shown in FIG.
Is in contact only with the region R1 of the spherical surface 2b, and does not come into contact with other portions of the slider portion 2a or the magnetic pole 7b.

Since the magnetic pole 7a is offset by ε away from the leaf spring 3 as shown in FIG. 3 or 5, a sufficiently large magnetic pole is employed under the condition that the magnetic pole 7a is disposed inside the region R2. can do.

As described above, according to the present embodiment, the gimbal 103 of the conventional example can be eliminated by making the surface of the magneto-optical disk 1 that contacts the sliding film 1d a spherical surface 2b.

Further, since the magnetic pole 7b can be arranged close to the region R1 where the sliding film 1d contacts, the change in the distance between the magnetic pole 7b and the recording layer 1b is reduced as compared with the conventional example, and stable recording is realized.

Since the spherical surface 2b protrudes from the magnetic pole 7b by a predetermined amount and uses the optimum design method as shown in FIG.
Even if the slider portion 2a has only the degree of freedom in the z-axis direction,
The sliding film 1d does not contact the magnetic pole 7b, and does not contact any portion other than the spherical surface 2b. Therefore, the sliding film 1d is not damaged. Further, the variation in the distance between the magnetic pole 7b and the recording layer 1b can be minimized.

Further, the magnetic pole 7b is moved away from the leaf spring 3 by ε.
By offsetting only by this, a sufficiently large magnetic pole 7b can be used.

Although the magnetic field modulation recording has been described as an example in the present embodiment, the magnetic head structure according to the present embodiment may be applied and used as a DC bias applying device depending on the device to which it is applied. In this case, a permanent magnet is mounted instead of the magnetic core 7 and the coil 8.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
Will be described with reference to FIGS. 7 and 8. FIG.

In this embodiment, an elliptical surface 2d shown in FIG. 7 is used in place of the spherical surface 2b of the magnetic head structure in the first embodiment. The major axis of the elliptical surface 2d is the x-axis as shown in FIG.
Direction. In addition, about what omitted description,
It is the same as in the first embodiment.

The projecting portion is elastically deformed when it comes into contact with the sliding film 1d, and at a certain moment, the contact point has a certain area. If this area is called a contact part and the shape is defined as a contact part shape,
When the protruding portion is the spherical surface 2b, the shape of the contact portion is a circle as shown in FIG. When the protrusion has an elliptical surface 2d, the contact portion has an ellipse as shown in FIG.

The effect of the present embodiment is that, since the contact portion has an elliptical shape, the contact surface pressure can be reduced.
The point is that the durability of the magneto-optical disk 1 can be improved. Generally, it is not desirable that the contact portion has a wide shape in the radial direction of the magneto-optical disk 1. This is because the sweep width increases in one sliding pass, and the probability of accumulation of dust and the like increases. Therefore, it is effective to align the major axis with the moving direction ω of the magneto-optical disk 1.

According to the present invention, even if the shape of the contact portion becomes elliptical, the gimbal 103 can be unnecessary, and there is no problem in operation. Generally, as the substantially spherical shape of the protruding portion in the present invention, a convex curved surface having a single contact portion and having no straight line in the outline of the contact portion shape can be adopted.

In the first and second embodiments described above, assuming that the recording area of the recording medium extends to the vicinity of the outermost periphery of the disk, the magnetic pole 7b is positioned at the center of the spherical surface 2b or the elliptical surface 2d. It has been described that the recording medium is offset from the outer periphery of the disk and farther away from the leaf spring 3. However, if the recording area of the recording medium is close to the center of the disk, the magnetic pole 7b is replaced by the spherical surface 2b or the elliptical surface. 2d
May be offset from the center of the disk on the inner peripheral side of the disk and on the side closer to the leaf spring 3.

[0059]

As apparent from the above description, the present invention can provide a high-efficiency magnetic head structure which is easy to manufacture at low cost.

That is, according to the magnetic head structure of the present invention, since the slider is provided with the projection, the sliding surface of the recording medium during operation can be used without using a complicated rotating mechanism such as a gimbal. The slider can be made to follow. Also,
By arranging the magnetic pole closer to the contact point with an offset on the outer peripheral side of the recording medium and far from the loading means,
Even if the recording medium is tilted, the sliding surface and the slider means are in stable contact, and a sufficiently large magnetic pole can be mounted.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a magnetic head structure according to a first embodiment of the present invention.

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a sectional view of a main part of FIG. 1;

FIG. 4 is a bottom view of a main part of FIG. 1;

FIG. 5 is a calculation diagram for designing a slider portion of the magnetic head structure according to the first embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of the magnetic head structure according to the first embodiment of the present invention.

FIG. 7 is an exemplary perspective view showing an elliptical projection of a magnetic head structure according to a second embodiment of the present invention;

FIG. 8 is a plan view showing the shape of a contact portion formed by a spherical projection of the magnetic head structure according to the first embodiment of the present invention.

FIG. 9 is a plan view showing a shape of a contact portion formed by a protrusion of an elliptical surface of a magnetic head structure according to a second embodiment of the present invention.

FIG. 10 is a perspective view showing a conventional magnetic head structure.

FIG. 11 is an enlarged perspective view showing a slider means of a conventional magnetic head structure.

[Explanation of symbols]

 Reference Signs List 1 magneto-optical disk (recording medium) 2 slider structure 2a slider portion 2b spherical surface 2d elliptical surface 3 leaf spring 4 fixing plate 7 magnetic core 7a side yoke 7b magnetic pole 7c center yoke 8 coil

Continuation of the front page (72) Inventor Toru Nakamura 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A magnetic head structure used for a disk-shaped recording medium having a sliding surface, a magnetic field generating means having a magnetic pole for applying a magnetic field to the recording medium facing the recording medium; Slider means attached to the recording medium and having a projection protruding from the magnetic pole toward the recording medium; and a part fixed to the slider means and substantially perpendicular to the sliding surface with respect to the slider means. Load means for applying a pressing force in any direction, and pressing the protruding portion against the sliding surface, wherein the slider means and the load means are arranged in series in the tangential direction of the recording medium, and the magnetic pole is A magnetic head structure, which is offset from a vertex of a protrusion in a radial direction and a tangential direction of the recording medium. 2. The magnetic head structure according to claim 1, wherein the magnetic pole is offset from an apex of the protrusion on an outer peripheral side of the recording medium and on a side farther from the loading unit. . 3. The magnetic pole is arranged such that the center of the magnetic pole is offset from the apex of the protrusion by about 1.2 mm or less on the outer peripheral side of the recording medium and by about 0.2 mm or less on the side farther from the loading means. The magnetic head structure according to claim 2, wherein: 4. The magnetic head structure according to claim 1, wherein the magnetic pole is offset from an apex of the protrusion on an inner peripheral side of the recording medium and on a side closer to the loading unit. body. 5. The magnetic head structure according to claim 1, wherein a periphery of the apex of the protrusion is a spherical surface. 6. The magnetic head structure according to claim 1, wherein a peripheral portion of a vertex of the protrusion has an elliptical surface.