KR960015989B1 - Junction ferrite magnetic head - Google Patents

Abstract

The junction ferrite magnetic head is made by adding a small amount of complex oxide such as CaO, ZrO2 and Na2O to polycrystalline ferrite, the side for forming main magnetic circuit in junction ferrite composed of single crystalline and polycrystalline ferrite and Fe2O3, MnO and ZnO as main composition, and selecting the single crystal ferrite with travelling side and direction having enhanced packing ratio.

Description

Junction Ferrite Magnetic Heads (96-15989)

1 is a manufacturing process diagram of a conventional single crystal and a head.

2 is a conventional magnetic head structure diagram.

3 is a general bonded ferrite and head manufacturing process diagram.

4 is a magnetic head structure diagram of the present invention.

5 is a single crystal orientation measurement and cutting processing state diagram.

6 is a structural diagram of a bonded ferrite.

7 is a graph showing the coefficient of thermal expansion and the coefficient of thermal expansion for polycrystals.

8 is a graph of surface roughness (Rmax) of a single crystal bonding surface.

9 is a graph of flatness (Flaxnes) of the single crystal junction surface.

10 is a graph of surface roughness of a polycrystalline bonding surface.

11 is a graph of flatness of the polycrystalline bonding surface.

12 is a schematic view of the Hot Pressing Furnace.

* Explanation of symbols for main parts of the drawings

1: monocrystalline ferrite 2: polycrystalline ferrite

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonded ferrite magnetic head. In particular, a small amount of complex oxide is added to a polycrystalline ferrite, which is a surface formed as a runner in a bonded ferrite composed of single crystal and polycrystalline ferrite, and the traveling surface and driving direction of the single crystal ferrite are adjusted. By selecting a high filling rate, the present invention relates to a magnetic head suitable for increasing the head characteristics and the service life.

Conventional magnetic heads for VCR imaging have been manufactured through a manufacturing process as shown in FIG. 1 as Mn-Zn based ferrite single crystals.

In other words, Fe ₂ O ₃ 53mo1%, MnO 28mo1%, ZnO 19mo1% is compounded according to the process of Figure 1 after the crystal growth through a number of processes, such as glass bonding bar (R) polishing process and R polishing process As shown in FIG. 2, an Mn-Zn ferrite single crystal VCR head having a head gap length and a head track width was manufactured. At this time, the tape sliding surface of the head was set to the (211) plane and the running direction was set to <111>.

Since such a conventional VCR has a high frequency of about 4-5 MHz, the technical response to the Mn-Zn-based ferrite single crystal was possible.

However, the characteristics of the head made of the conventional single crystal alone are not suitable for the head of the Hi-Fi 8mm camcorder and the head of the super VHS VCR due to the decrease in the reproduction output characteristics in the high frequency band (more than 5 MHz) and the increase of rubbing noise. .

Particularly, when the single crystal ferrite is used as the main runner, the magnetic domain is easily deformed during tape driving, thus providing high sensitivity image quality in the 8MHz high frequency band due to low noise ratio (S / N) characteristic of the single crystal. Can not.

The characteristics after the single crystal and head fabrication have a high noise value of about 5-8 dB as shown in (Table 1). In addition, in the regeneration output of the head (R / P output), it has a low value of about 150-2l0 하는데, which is active in the electron hopping phenomenon of the single crystal ferrite (a phenomenon that reduces the electrical resistance due to the active movement of the electrons). This is due to the low value. Therefore, in order to improve the above-mentioned problem, a head in which runner-forming surfaces are made of polycrystals and tape-contacting surfaces are made of single crystals is known (Japanese Laid-Open Patent Publication No. 57-205817 and Japanese Laid-Open Patent Publication No. Hei 3-171407).

In this way, when the surface formed by the runner is polycrystalline, the high frequency characteristics are excellent, and the material itself has a grain boundary, which fixes the earth so that no noise is generated.

Such a bonding head is generally manufactured through a process as shown in FIG. However, the junction head has a low reproduction power and high rubbing noise in the 8 MHz band. And there is a problem such as the service life is somewhat reduced.

Accordingly, the present invention has been made to solve the above-described conventional problems, and the surface and the direction of adding a small amount of oxide to the polycrystalline ferrite simulated surface formed as a runner and having a wear resistance on the surface and the direction of the single crystal in contact with the tape. It is an object of the present invention to provide a head which improves the head characteristics (improved reproduction power, reduces friction noise) and extends the service life.

Hereinafter, the present invention will be described.

4 is a structural diagram of the magnetic head of the present invention. The present invention relates to a structure in which a single crystal and a polycrystalline ferrite are formed as runners in a bonded ferrite composed of Fe ₂ O ₃ , MnO, and ZnO. It is formed by adding CaO, ZrO ₂ , Na ₂ O to the simulated properties of the polycrystalline ferrite 2.

The addition ratio of CaO, ZrO ₂ and Na ₂ O which is CaO and ZrO ₂ are each from 0.02 to 0.1 mol% with respect to the polycrystalline ferrite composition Mo, Na ₂ O is composed of 0.02 to 0.1 weight percent. In addition, the tape contact surface of the single crystal ferrite 1 is set to the (110) surface, and the running direction of the head is set to the <211> direction.

In the present invention, by adding CaO, ZrO ₂ , Na ₂ O to the polycrystalline ferrite replica formed as a runner, the sliding noise is greatly improved along with the high frequency characteristics at 8 MHz.

In addition, when the tape contact surface is a single crystal, the single crystal has various surface indices. Among them, as shown in Figs. 5 and 6, the (110) plane having the highest atomic filling rate is used as the tape contact surface, and the head running direction is monocrystalline. By providing a relatively high atomic loading density in the <211> direction, even a single crystal having the same composition is excellent in wear resistance.

The following is described according to the embodiment.

Example 1

This example is for comparing the polycrystalline characteristics of the present invention with those of conventional crystals (polycrystals, single crystals) as shown in (Table 2).

First, the conventional single crystal was measured by XRF composition with the ingot (ingot) grown by the continuous vertical Bridgman method through general powder metallurgy method as the starting chemical composition as shown in Table 2, and the site was also subjected to toroidal processing. The initial permeability was measured at 0.5MHz and 8MHz by using and the electrical resistivity was measured by 4prove terminal. In addition, the B ₁₀ value of the saturation magnetic flux density was measured at 100e (Oersted).

In order to measure the coefficient of thermal expansion important for ferrite bonding, the sample was made into a rectangle of 5 ^W x 5 ^O x 25, and the Dilatermeter instrument measurement was made up to 800 ° C as shown in FIG.

The conventional polycrystal, which is formed as a runner of the head, is made of a process as shown in FIG. 3, and is mixed with a starting chemical composition as shown in Table 2, and then pressed to a desired size through wet milling and spray drying. The green molded body was produced by pressing high density polycrystalline ferrite at 300 kg / cm 2 pressure for 3 hours at 1300 ° C. in a nitrogen atmosphere using a hot press.

Meanwhile, as shown in Table 2, the polycrystalline ferrite of the present invention has 0.05 mol% of CaO and ZrO ₂ and 0.05 of Na ₂ O in Fe ₂ O ₃ , MnO, and ZnO having the same simulated composition as the polycrystalline composition described above. After the addition by weight, the same process as in the above-mentioned polycrystalline ferrite manufacturing process was performed (FIG. 3).

The measurement conditions for comparing the properties of the above-described conventional and polycrystalline ferrites of the present invention were the same as the single crystal measurement conditions described above.

As a result, as shown in (Table 2), the polycrystalline ferrite of the present invention showed a much better value in electrical resistivity and high frequency characteristics (8MHz), and the saturation magnetic flux density was around 5000gauss.

In addition, the present invention has no significant difference in thermal expansion coefficient as compared with the prior art, and there is no problem in the bonding process if the difference in mutual thermal expansion coefficient is within ± 10%.

Example 2

In this example, the characteristics in the state in which the monocrystalline ferrite and the polycrystalline ferrite were bonded were examined. The results are shown in Table 3 below.

The single crystal ferrite used in the present invention was etched in a 30% hydrochloric acid solution for 3 minutes in a disk having the same composition ratio as Comparative material B, and then cut along the <111> and <211> directions, and the size thereof was 45 ^It was mirror polished with diamond 0.1 μm abrasive so that R max (maximum surface roughness) and flatness (flatness) of the joint surface were set to ^W × 35 ^D × 1.5 ^t .

Meanwhile, the high-density ferrite polycrystal of the present invention is a polycrystalline ferrite prepared by adding 0.05 mol% CaO and ZrO ₂ and 0.05 wt% Na ₂ O, respectively, to the dummy properties shown in Table 3 for the purpose of improving head characteristics. 45 ^W x 35 ^D x 1.5 ^t was cut and mirror-polished so that the Rmax and the flatness of the bonding surface were 0.5 µm or less in the same manner as the polishing polishing in the single crystal described above.

Thus, the surface roughness was 0.014 mu m and the flatness was 0.11 mu m as shown in FIGS. 8 (surface roughness) and 9 (flatness) after the mirror polishing. In addition, as shown in Figs. 10 (surface roughness) and 11 (flatness), the polycrystalline bonded mirror surface had a surface roughness of 0.02 µm and a flatness of 0.15 µm, indicating that they were satisfactory mirror surfaces.

And, Figure 6 each junction to give paint with acetone to the front after one another butt joint of claim 12 degrees (Hot Pressing Furnace schematic view) and the joined in the use of SiC + Si ₃ N ₄ mold such devices ferrite specimen, as shown in Surrounded by alumina powder (Al ₂ O ₃ Powder) 80mesh ≒ 300㎛ particle size, hot pressurized at 5 ℃ / ㎠ for 30 minutes at 1200 ℃ for grain growth in single crystal grain direction. It was fully bonded and the yield strength at that time was 12 kg / mm 2 (measured by 4 point support method). In order to know the characteristics of the head, the gap length of the head is 0.37㎛ and the track width as shown in Fig. 4 through the material bar processing and the glass bonding bar and R polishing process after the hot working process. width of 31㎛ and mounted on the VCR Drum, the head reel output and Rubbing Noise characteristics were measured at 5.8m / sec head / tape speed in S / P mode. In consideration of the filling rate, the tape contact surface was made into the (110) plane and the running direction of the head was made to be <211>.

On the other hand, in order to compare with the present invention (Table 3) in the conventional comparative material A (single crystal and polycrystalline junction ferrite) the polymorphism of the chemical crystallinity of only Fe ₂ O ₃ , MnO, ZnO, the chemical composition of the single crystal (Table It carried out similarly to the comparative material B in 3). And the head preparation was carried out similarly to the method mentioned above.

As a result, as shown in (Table 3), the present invention is superior to the regeneration output, which is a high frequency characteristic, compared to the comparative materials A and B heads. More than 20% improvement over the prior art.

Example 3

This Example is to investigate the head characteristics according to the addition range of CaO, ZrO ₂ , Na ₂ O added to the polycrystalline imitation property, the same method as in Example 2 in the composition ratio range as the samples 1 to 6 of (Table 4) The bonding head was produced.

As a result, when CaO and ZrO ₂ were 0.01mo1% or less, and Na ₂ O was 0.01% by weight or less, the high frequency characteristics were hardly observed. Caused. Accordingly, it was found that CaO and ZrO ₂ were 0.02-0.lmol% and Na ₂ O was good at 0.02-0.1% by weight.

In addition, the head life of the head was different depending on the driving surface / driving direction configuration. It can be seen that more than 20%.

Table 1 Characteristics of conventional single crystal and post head manufacturing

[Table 2 Characteristics of Head Material]

TABLE 3 Characteristics between the present invention and the comparative material

[Table 4 Head characteristics according to the additive composition ratio of the present invention]

Claims (3)

In the bonded ferrite of monocrystalline and polycrystalline ferrite composed of Fe ₂ O ₃ , MnO, and ZnO, CaO, ZrO ₂ and A bonded ferrite magnetic head characterized by adding Na ₂ O. 2. The bonded ferrite magnetic head according to claim 1, wherein the tape contact surface of the single crystal ferrite is a (110) plane, and the running direction of the head is a <211> direction. The bonded ferrite magnetic head according to claim 1 or 2, wherein CaO and ZrO ₂ are 0.02-0.lmo1% and Na ₂ O is 0.02-0.1% by weight, respectively. .