JP3152811B2 - Non-magnetic single crystal processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for performing fine processing of irregularities on the surface of a Ca ₂ Fe ₂ O ₅ single crystal which is a non-magnetic single crystal material, for example, a hard disk for a computer, a floppy disk, and a magnetic tape. The present invention relates to fine processing of a shape of a magnetic medium facing surface in a slider of a magnetic head using a calcium iron composite oxide single crystal, particularly for use in magnetic recording of an audio recorder, a video tape recorder, or the like.

[0002]

2. Description of the Related Art In recent years, a magnetic recording apparatus using a magnetic head has been increasing in recording density and capacity, and accordingly, the magnetic head has been adapted to higher linear density and higher track density. Is required. In recording on a magnetic disk using such a magnetic head, a composite slider is employed as one of the methods for achieving a high linear density and a high track density corresponding to an increase in capacity.

As a characteristic required for such a slider material, it is necessary to have excellent slidability with a magnetic medium. The track density of the high-density recording head is 10 μm.
The following is required, and the material of the slider used for this is required to have few pores.

Further, in a magnetic head for a hard disk, a CS which causes the head to fly as the disk rotates.
A method called S (Contact Start / Stop) is employed. In this CSS method, the disk and the head come into contact and slide when the disk is started and stopped. Therefore, if there is a pore in the slider part when sliding, lubricant or magnetic powder or the like adheres to the pore part or adheres from the pore part, thereby destroying the magnetic medium, destroying the data or And the reliability of the magnetic recording device is significantly reduced. Especially in recent years, the distance between the magnetic disk and the head during operation (flying height)
And the magnetic film of the magnetic disk is thinner, which makes it easier to break. From this point, a material having a small pore size is required for the slider material.

When the distance between the magnetic disk and the head is 0.
If it is 15 μm or less, the flying height is large at the outer peripheral portion and the flying height is small at the inner peripheral portion due to the difference in the peripheral speed between the inner and outer peripheries of the disk. As a countermeasure, a method of giving a slider a skew angle (an angle between a slider rail and a tangential direction of a disk) is often used. However, even if this method is adopted, it is difficult to obtain a uniform floating amount of the inner and outer circumferences. Therefore, a method has been developed in which a concave portion is formed on the air bearing surface and a negative pressure portion is provided to make the floating amount on the inner and outer circumferences constant.

At present, as a slider material, calcium titanate, barium titanate, alumina-titanium carbide material, non-magnetic zinc ferrite and the like are used.
00 to 120 × 10 ^-7 / ° C, 80 for barium titanate
~ 100 × 10 ^-7 / ° C, 75 for alumina-titanium carbide
× 10 ^-7 / ° C, 90 × 10 ^-7 for nonmagnetic zinc ferrite
/ ° C. On the other hand, Mn-Zn ferrite having high magnetic permeability is generally used as a head core,
The thermal expansion coefficient of this Mn-Zn ferrite is 110 × 10
^-7 / ° C. to 120 × 10 ^-7 / ° C., and a calcium titanate-based slider material is often used as a nonmagnetic slider material that can be used for the ferrite core. In the thin film head, an alumina-titanium carbide material is used.

[0007]

However, in the conventional slider material for a magnetic head, according to the method of forming a concave portion on the floating surface and providing a negative pressure portion to make the floating amount on the inner and outer circumferences constant, A recess formed in such a slider needs to be machined to a depth of several μm, and there is a problem that it is difficult to machine a recess of several μm by conventional mechanical grinding. The reason why the workability is a problem is that the slider material having excellent fine workability facilitates mass production of the magnetic head and improves the productivity.

[0008] Also, calcium titanate, a non-magnetic slider material that can be used for the Mn-Zn ferrite core, and alumina-titanium carbide, which is used for the thin-film head, are polycrystalline materials, so that the slider's floating surface is finely processed. There was a problem that was difficult. This is because uniform processing is difficult due to differences in crystal orientation and grain boundaries on the processing surface when processing fine processing by ion etching (ion milling) or the like in a polycrystalline body. In addition, in the conventional polycrystalline material, pores and the like are generated at the crystal grain boundaries, and there is a limit in improving the sliding characteristics.

Further, these calcium titanate, barium titanate, and alumina-titanium carbide are all sintered bodies, have high chemical stability, and cannot be etched in a short time by dilute hydrochloric acid or the like. Even if etching is performed using hot phosphoric acid or the like, it is difficult to select a resist film having high heat resistance, and since the resist film is polycrystalline, the etched surface becomes uneven as shown in FIG. Cannot be machined on a high surface.

On the other hand, there is a monolithic slider material made of a magnetic material using a single crystal. This is Mn
-It is a magnetic material that employs a Zn ferrite single crystal, and it is difficult to produce a magnetic head with small sliding noise.

The present invention provides a method for processing a non-magnetic single crystal which can be applied to sliders and electronic parts of various magnetic heads, is easy to perform fine processing by etching, has a small friction coefficient with a magnetic medium, and has excellent sliding characteristics. To provide.

[0012]

Means for Solving the Problems As a result of repeated studies in view of the above situation, the present inventor has found that a non-magnetic single crystal composed of Ca ₂ Fe ₂ O ₅ having no grain boundaries and having a uniform crystal orientation can be used, for example. It has been found that when applied to slider materials and various electronic parts, there is no pore, and sliding characteristics and fine processing are good. Further, the nonmagnetic single crystal made of Ca ₂ Fe ₂ O _{5 was found} to be easily chemically etched by an acidic solution, easily ion-etched by ion beam irradiation, and easy to perform fine processing. The present invention has been made.

That is, according to the present invention, a resist pattern is formed on the surface of a non-magnetic single crystal made of Ca ₂ Fe ₂ O _5, and the surface of the non-magnetic single crystal is brought into contact with an acidic solution to perform chemical etching or the aforementioned non-magnetic single crystal. The surface is irradiated with an ion beam to perform ion etching.

As described above, by using a single crystal made of Ca ₂ Fe ₂ O ₅ for, for example, a non-magnetic material for a slider of a magnetic head, various electronic parts, precision mechanical parts, etc., the composition is rich in resources. By using an oxide of calcium and iron, an inexpensive industrial material can be provided as compared with expensive Mn-Zn ferrite or the like.

The single crystal made of Ca ₂ Fe ₂ O ₅ uses commercially available iron oxide having a purity of 98% or more.
Calcium chloride (C) as a source of calcium oxide (CaO)
aCl ₂ ), calcium carbonate (CaCO ₃ ), etc., are weighed so that the composition ratio of CaO is 2 mol and Fe ₂ O ₃ is 1 mol, and wet-mixed using a ball mill. This is dried, and the raw material after drying is
Perform calcination for 10 hours. The calcined raw material is pulverized using a solvent and pulverized so that the average particle size becomes about 3 μm.

After adding a binder to the mixture and performing granulation, the mixture is molded at a pressure of 0.8 to 3 ton / cm ² . Then one
It is fired at 150 ° C to 1350 ° C to obtain a material bar.

The obtained polycrystalline material rod is mounted on a material mounting jig of a floating zone melting apparatus (FZ method), and the seed crystal is mounted on the other axis to form a molten zone while rotating in the opposite directions. The melting zone is moved at a speed of 1 to 10 mm / h, and a single crystal composed of Ca ₂ Fe ₂ O ₅ is obtained by a floating melting method.

In addition, using this material, the same Ca ₂ Fe can be obtained by the CZ method, the Bridgman method, the flux method or the like.
_A single crystal of ₂ O ₅ is obtained.

For processing a non-magnetic single crystal made of Ca ₂ Fe ₂ O ₅ , a resist pattern made of, for example, ethyl cellosolve acetate is applied to the surface thereof, and thereafter, for example, hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid is used. A non-magnetic single crystal having a resist pattern formed thereon is immersed in an acidic solution of 5 to 75% for 1 to 60 minutes, and the surface of the non-magnetic single crystal is brought into contact with the acidic solution to form a resist pattern other than the resist pattern. Is etched. Then, the resist pattern is immersed in a stripping solution and removed.

In the processing of a nonmagnetic single crystal made of Ca ₂ Fe ₂ O ₅ , a resist pattern made of, for example, ethyl cellosolve acetate is applied to the surface thereof, and gallium ions, argon, etc. are formed by, for example, an ion beam processing apparatus. A portion other than the resist pattern is etched by irradiating a focused beam (FIB) of a predetermined diameter made of ions. Then, the resist pattern is immersed in a stripping solution and removed. Incidentally, the portion other than the pattern may be etched by controlling the irradiation position of the ion beam without forming the resist pattern on the surface of the nonmagnetic single crystal.

[0021]

In the non-magnetic single crystal material used in the present invention, a non-magnetic single crystal made of Ca ₂ Fe ₂ O ₅ having no grain boundaries and having a uniform crystal orientation is used, for example, as a material for a slider of a magnetic head. Is a non-magnetic material having few pores, a small coefficient of friction with a magnetic medium, and excellent sliding characteristics.

Then, a resist pattern is applied to the surface of the non-magnetic single crystal made of Ca ₂ Fe ₂ O ₅ and immersed in an acidic solution such as dilute hydrochloric acid to bring the surface of the non-magnetic single crystal into contact with the acidic solution. Chemical etching, or, for example, ion etching by irradiating gallium ions to the surface of the non-magnetic single crystal, and etching the non-resist pattern other than the non-magnetic single crystal of Ca ₂ Fe ₂ O ₅ An uneven pattern can be easily formed on the surface. According to the above-described chemical etching method, the type of solution, immersion time, and concentration are controlled, and according to the ion etching method, the focusing diameter, the type of ion source, the applied voltage, the applied current, and the applied time are controlled. By controlling, fine processing of about nanometer (0.001 μm) can be performed.

[0023]

EXAMPLE Using commercially available iron oxide having a purity of 99.99%, calcium carbonate (CaCO ₃ ) as a calcium oxide (CaO) source, ₂ moles of CaO and Fe ₂ O ₃ 1
It was weighed so as to have a molar composition ratio, and was wet-mixed using a ball mill. This is dried, and the raw material after drying is 800
Calcination was performed at 10 ° C. for 10 hours. The calcined raw material was pulverized using a solvent and finely pulverized so that the average particle size became about 3 μm.
After adding the binder and granulating, 2 tons / c
Molded at a pressure of m ² . Thereafter, firing was performed at 1240 ° C. to obtain a material bar.

The obtained polycrystalline material rod was mounted on a material mounting jig of a floating zone melting apparatus (FZ method), and the seed crystal was mounted on the other axis to form a molten zone while rotating in the opposite directions. / H to move the melting zone,
A single crystal composed of Ca ₂ Fe ₂ O ₅ was obtained by the floating zone melting method.

The grown material was cut, processed into a slider shape having two rails with a width of 525 μm, and set on a 1250 Oe magnetic disk via a mounting bracket. Then, the rotation and stop (CSS) were repeated with the maximum rotation number of the disk set to 3600 rpm. That is, the time required for the disk to reach the maximum rotation speed is 5 seconds, and the maximum rotation speed is 5 seconds.
Hold for 2 seconds. In addition, the number of CSSs was set to one cycle of 20 seconds from the stop state to the stop and the stop, with the stop time being 5 seconds. Table 1 shows the relationship between the number of CSSs and the friction coefficient of Ca ₂ Fe ₂ O ₅ single crystal and CaTiO ₃ polycrystalline material as a comparative example.

[0026]

[Table 1]

From Table 1, it can be seen that the single crystal material of Ca ₂ Fe ₂ O ₅ has a small increase in the coefficient of friction due to an increase in the number of CSSs, as compared with the conventional slider material CaTiO ₃ polycrystalline material.
The sliding characteristics were excellent.

In addition, a Ca ₂ Fe ₂ O ₅ single crystal material and Ca
After performing CSS a predetermined number of times using the TiO ₃ polycrystalline material, the presence or absence of scratches on the media and the presence or absence of scratches on the slider were observed with a metallographic microscope. The results are shown in Table 2.

[0029]

[Table 2]

As shown in Table 2, the media and the slider (sample No. 1) subjected to CSS using the Ca ₂ Fe ₂ O ₅ single crystal slider showed no damage up to 60,000 times. On the other hand, when the CSS was performed using the CaTiO ₃ polycrystalline material (Sample No. 2, 2), the media was damaged after 40,000 times, and the media and the slider were damaged after 60,000 times.

Further, in the recesses and rails on the floating surface of the slider, the surface of the single crystal material is mirror-finished, and a part of the mirror surface is covered with a resist film made of ethyl cellosol acetate. By immersing it in an acidic solution held for a certain period of time. Thereafter, the resist pattern was immersed in a stripping solution and removed. Table 3 shows the relationship between the etching time and the etching depth. For comparison, a polycrystalline material made of CaTiO ₃ was similarly etched. 1 and FIG. 2 show the surface state of the Ca ₂ Fe ₂ O ₅ single crystal and the CaTiO ₃ polycrystal on the etched surface using a stylus type surface roughness meter.
It was shown to.

[0032]

[Table 3]

From Table 3, according to the processing method of the present invention, the etched surface is smoother than the surface etched with the polycrystalline material as shown in FIG. 1, and the etching depth is directly proportional to time. It was found that the control of the processing amount was easy.

A description will be given of an example in which a concave portion or a rail on the air bearing surface of a slider is ion-etched using an ion beam. First, after the surface of the single crystal material is mirror-finished, a part of the mirror surface is covered with a resist film made of ethyl cellosol acetate, and an ion beam processing device (trade name:
Gallium ions using a SMI-8100 (manufactured by Seiko Instruments Inc.) at a voltage of 30 kV and a current of 1.5 nA.
Under the condition described above, the focused beam (F
By scanning and irradiating IB) on the processing target portion for 30 minutes, the Ca ₂ Fe ₂ O ₅ single crystal material was processed. The scanning area was 14 × 14 μm. Thereafter, the resist pattern was immersed in a stripping solution and removed.

The work surface was a mirror surface, and the edge of the work was machined so that the depth could be easily measured. After processing, the processed surface (upper surface) and the cross section (side surface) were observed by SEM to evaluate the shape. 3A and 3B show a state of a machined surface according to the present invention, wherein FIG. 3A is a sectional view and FIG. 3B is a plan view.
For comparison, a polycrystalline material made of CaTiO ₃ and a polycrystalline material made of Al ₂ O ₃ —TiC were similarly subjected to ion etching, and Ca ₂ Fe ₂ O
₅ Single crystal material, polycrystalline material composed of CaTiO ₃ , Al
Table 4 shows the etching depth and the etching rate of the polycrystalline material and polycrystalline ferrite made of ₂ O ₃ —TiC, and the state of the etched surface was observed by SEM.

[0036]

[Table 4]

FIG. 4 shows the state of the etched surface of a polycrystalline material composed of Mn--Zn ferrite, and FIG.
The state of the etched surface of the polycrystalline material consisting _3, 6 is a state of the etched surface of the polycrystalline material comprised of Al ₂ O ₃ -TiC, respectively (a) is a sectional view, (b)
Is a plan view.

In this processing method, the etched surface is superior in smoothness to the surface etched with the polycrystalline material as in the case shown in FIG. 1, and the etching depth is directly proportional to time. It turned out that it was excellent in workability.

The coefficient of thermal expansion of the single crystal of Ca ₂ Fe ₂ O _{5 of} the present invention can be controlled in the range of 80 to 210 × 10 ⁻⁷ / ° C., and the coefficient of thermal expansion of Mn—Zn ferrite is 110. It is possible to easily cope with × 10 ⁻⁷ / ° C. to 120 × 10 ⁻⁷ / ° C.

In the above embodiment, the CZ is obtained by the FZ method.
Although an example in which a single crystal made of a ₂ Fe ₂ O ₅ is prepared has been described, the same single crystal can be obtained from the Ca ₂ Fe ₂ O ₅ of the present invention also by the CZ method, the Bridgman method, and the flux method.

Further, in the above embodiment, Ca ₂ Fe ₂ O ₅
An example in which a single crystal consisting of is applied to a slider material of a magnetic head and chemically or ion-etched with an acidic solution has been described, but the present invention is not limited to the above-described embodiment, and Ca ₂ Fe ₂ O ₅ For example, when a single crystal made of is applied to an electronic component such as a sensor or a precision machine component, chemical etching or ion etching may be performed using an acidic solution.

Further, in the above embodiment, an example in which gallium ions are irradiated has been described. However, the present invention is not limited to the above embodiment, and other ions generally used for ion etching may be used. Of course.

[0043]

As described in detail above, according to the present invention, C
A resist pattern is applied to the surface of a non-magnetic single crystal composed of a ₂ Fe ₂ O ₅ and immersed in, for example, an acidic solution such as dilute hydrochloric acid, and the surface of the non-magnetic single crystal is brought into contact with an acidic solution,
Or, by irradiating gallium ions and chemically etching or ion-etching a portion other than the resist pattern, an uneven pattern having excellent smoothness can be easily formed on the surface of the nonmagnetic single crystal made of Ca ₂ Fe ₂ O _5. Can be.

In addition, Ca ₂ having no grain boundaries and having a uniform crystal orientation is used.
For example, when a non-magnetic single crystal made of Fe ₂ O ₅ is used as a material for a slider of a magnetic head, a non-magnetic material having no pores, a small friction coefficient with a magnetic medium, and excellent sliding characteristics is used. Obtainable.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state in which a surface of a nonmagnetic single crystal made of Ca ₂ Fe ₂ O ₅ is chemically etched with an acidic solution.

FIG. 2 is a longitudinal sectional view showing a state in which the surface of a polycrystal made of CaTiO ₃ is chemically etched.

3A and 3B show a state of an etched surface by ion etching according to the present invention, wherein FIG. 3A is a cross-sectional view and FIG. 3B is a plan view.

4A and 4B show a state of an etched surface of a polycrystalline material made of Mn—Zn ferrite by ion etching, wherein FIG. 4A is a cross-sectional view and FIG. 4B is a plan view.

FIG. 5 shows a state of an etched surface of a polycrystalline material made of CaTiO ₃ by ion etching, and FIG.
Is a sectional view, and (b) is a plan view.

6A and 6B show a state of an etched surface of a polycrystalline material made of Al ₂ O ₃ —TiC ₃ by ion etching, wherein FIG. 6A is a sectional view and FIG. 6B is a plan view.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI G11B 21/21 101 G11B 21/21 101K (58) Field surveyed (Int.Cl. ⁷ , DB name) C30B 1/00-35 / 00 G11B 5/127 G11B 5/60 G11B 21/21 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] A resist pattern is formed on the surface of a non-magnetic single crystal made of Ca ₂ Fe ₂ O _5, and the surface of the non-magnetic single crystal is brought into contact with an acidic solution for chemical etching or ion beam irradiation on the surface of the non-magnetic single crystal. A non-magnetic single crystal, characterized in that the non-magnetic single crystal is irradiated by ion irradiation.