JPS6297114A - Magnetic head - Google Patents

Abstract

PURPOSE:To obtain a magnetic head having high strength of grain boundary and large initial magnetic permeability and magnetic flux density by incorporating silicon oxide and calcium oxide into manganese-zinc ferrite contg. 53-53mol% Fe2O3 and 17-19mol% ZnO. CONSTITUTION:The magnetic head is formed by using the core which consists of the material formed by incorporating <=0.02wt% silicon oxide and/or <=0.08wt% calcium oxide into the mangansezinc ferrite contg. 52-53mol% Fe2O3 and 17-19mol% ZnO and has <=80mum average grain size and >=8,000 initial magnetic permeability at 40 deg.C and 100kHz. The strength of grain boundary in the front core thereby increased and the extremely good magnetic characteristics including the large initial magnetic permeability and max. magnetic flux density in the high frequency region of 50-300kHz and the small magnetic loss are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field The present invention relates to a magnetic head. More specifically, the present invention relates to improvements in manganese-zinc ferrite cores used in floppy disk heads.

As a material for the prior art magnetic head core, manganese-zinc ferrite is commonly used. Among ferrites, this material has high magnetic permeability and saturation magnetic flux density, and is suitable for use at low frequencies of about 100 KHz or less, and is also used as a core material for floppy disk heads.

By the way, the initial magnetic permeability of manganese-zinc ferrite is
It shows dependence on temperature as well as frequency, and the temperature change of this initial magnetic permeability usually has a first peak near the Curie temperature and a second peak near room temperature.

It has been confirmed that under normal mounting, the temperature of the sliding surface of the floppy head is approximately 40°C.

Therefore, when using the above manganese-zinc ferrite as the core material of the floppy head core, in order to obtain a larger initial permeability, the absolute value of this value must be increased, and the second peak mentioned above must be increased. It is necessary to set the composition of the core material so that the temperature is around 40°C.

In addition, it is also necessary to obtain a high magnetic flux density at this temperature.

By the way, for the ferrite core of a magnetic head for floppies, etc., the strength of the grain boundaries must be extremely high.The front surface of the magnetic head core is mirror-polished and polished, and is used for recording and reproducing. This is because the grain boundaries are sometimes in sliding contact with the recording medium, and the strength of the grain boundaries is small, and if the grains fall off on the medium, it will cause serious trouble.

However, all conventional Mn-Zn-based ferrites have low grain boundary strength, and many defective products have been found where grains may fall off during inspection.

Therefore, it is desired to develop a magnetic head that has high grain boundary strength and, as described above, that can provide good magnetic properties in practical use.

(2) Purpose of the Invention It is an object of the present invention to provide a magnetic head with high grain boundary strength and high initial magnetic permeability and magnetic flux density in practical use.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the first invention provides a manganese-zinc ferrite containing 52 to 53 mol% of Fe2O3 and 17 to 19 mol% of ZnO, and 0.02% by weight or less of silicon fermentation and/or 0.08% of calcium oxide. It is a material containing % by weight or less, has an average grain diameter of 80 uL11 or less, and has an initial magnetic permeability of 800 at 40°C and 100 KHz.
0 or more cores, recording frequency 50-300 KHz
This is a magnetic head characterized by being used in.

Moreover, the second invention contains 52 to 53 mol% of Fe2O3,
A material containing 0.102% by weight or less of silicon oxide, 0.02% by weight or less of calcium oxide, and 0.02% by weight or less of niobium oxide in a manganese-zinc ferrite containing 17 to 19 mol% of ZnO. The average grain diameter is 80p layer or less, 40℃, 1
Has a core with an initial permeability of aooo or more at 00 KHz.
This magnetic head is characterized in that it is used at a recording frequency of 50 to 300 KH2.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The core material of the magnetic head of the present invention includes a manganese-zinc ferrite containing 52 to 53 mol% of Fe2O3 and 17 to 19 mol% of Zn, and a small amount of silicon monoxide and/or calcium oxide. and,
Furthermore, niobium oxide is contained as necessary.

Silicon oxide, which is an additional element contained, is a component particularly for improving magnetic permeability and reducing magnetic loss.
The content of silicon oxide is 0.02% by weight or less, especially 0.0%
A range of 1 to 0.015% by weight is preferred.

On the other hand, calcium oxide also improves magnetic permeability,
Moreover, it is intended to reduce magnetic loss, and its content is preferably 0.08% by weight or less, particularly preferably in the range of 0.02 to 0.05% by weight.

Although only one of these two components may be added, in the present invention, it is preferable to use both of them together since they exhibit a synergistic effect, particularly in terms of improving the initial magnetic permeability.

If the silicon oxide content exceeds 0.02% by weight, the strength of grain boundaries will decrease, and if the calcium oxide content exceeds 0.08% by weight,
The strength of grain boundaries decreases.

Furthermore, in the present invention, it is preferable to contain niobium oxide in an amount of 0.02% by weight or less, particularly in the range of o, oto to 0.015% by weight. By adding niobium oxide, the magnetic permeability is further improved. , and the magnetic loss is reduced.

However, if niobium oxide exceeds 0.02% by weight, the grain boundary strength of the grains decreases.

Furthermore, the total content of calcium oxide, silicon oxide, and niobium oxide is 0.09% by weight or less, preferably 0.04 to 0.08% by weight.

If the total content exceeds 0.09% by weight, the strength of grain boundaries decreases.

In addition, the manganese-zinc ferrite composition used in the present invention includes 52 to 53 mol% of Fe2O3 and 17% of ZnO.
~19 mol% is because the combination of the ferrite composition in this composition range and the additives mentioned above improves the absolute value of magnetic permeability, and also increases the initial permeability and This is because excellent magnetic properties such as having the highest magnetic flux density can be obtained.

Good magnetic properties cannot be obtained with compositions other than this.

The core of the magnetic head of the present invention made of such a material is molded by the process described below, and the average grain diameter of the core for the magnetic head after molding is preferably 80 p, ta or less, particularly 10 to 50 ha. . This value is 80p
If it exceeds m, the strength of the grain boundaries will decrease, and furthermore, magnetic loss will increase, resulting in poor magnetic properties.

Such average grain diameter is J I 5-C-256
It is calculated using the following formula according to 3.

D=1/NXL/nX1000 (μm) where D=
Average crystal grain size N: Magnification of the microscope L: Length of a straight line (mm) n: Number of particles cut by a straight line The one-dimensional value calculated using the above formula is roughly π
The three-dimensional value calculated by multiplying by /2 is the average grain diameter DO in the invention.

DO=DXπ/2 Furthermore, the density of the core is preferably 99.5% or more of the theoretical density, especially 99.8 to 100%. This reduces the strength of the grain boundaries and increases the density in the high frequency range. Improves magnetic properties.

The core of the magnetic head of the present invention is generally manufactured as follows.

That is, a predetermined amount of the above composition is mixed in powder form. For mixing, wet mixing such as an attritor is usually used.

Next, it is dried, calcined, pulverized with a ball mill, etc., and then dried. Thereafter, after molding according to a conventional method such as so-called cold pressing, the molding process was performed at 1100-1400°C in a non-oxidizing atmosphere.
Primary firing is performed until the density reaches 95 to 98% of the theoretical density.

Then 99.5% of theoretical density at 1100-1400°C while pressurized to at least 800 Kg/cm'.
The secondary firing is performed until the percentage is more preferably 99.8% or more.

That is, in the secondary firing step, a dense coating layer is formed to close the communicating holes, and then in the secondary firing step, the material is compacted under external pressure to form a sintered body with desired magnetic properties.

When manufacturing the core of the magnetic head of the present invention, instead of the silicon oxide, calcium oxide, and niobium oxide described above, substances that can be converted into these substances by firing, such as carbonates, bicarbonates, and hydroxides, are used. It can also be used.

Further, the non-oxidizing atmosphere for the second firing can be formed using, for example, an inert gas or an inert gas with a controlled oxygen concentration, or can be formed by reducing pressure.

Pressure in the secondary firing can be performed using, for example, a hot isostatic press device.

In order to arbitrarily control the average grain size of the core material in the present invention to some extent, the preliminary firing temperature may be varied between 800 and 1000°C and the secondary firing temperature between 1250 and 1350°C during the manufacturing process.

Such a core has a maximum magnetic flux density of 40°C, direct current,
15Oe Bts is 4500G or more, especially 4500~4
900G is shown.

Also, 40℃, 0,5mA, 100KHz
1) Initial magnetic permeability of 8000 or more, especially aooo~12000.

When a recording frequency of 50 to 300 KHz, particularly 1f125KHz, 2f250KHz, or 1f67.5KHz, 2f125K)lz is used for a 70-7 speed disc, it exhibits extremely good electromagnetic conversion characteristics.

There is no particular restriction on the shape of the core of the magnetic head of the present invention, and it may be of various known shapes, for example core shapes used in floppy heads such as so-called bulk type, laminate type, tunnel erase type, etc. The surface is mirror-polished, a slide etc. is attached in accordance with the usual method, and a magnetic head is assembled.

The core of the present invention has an extremely high grain boundary strength, that is, even under extremely severe conditions such as etching with a 25% hydrofluoric acid (HF) aqueous solution for 2 minutes at room temperature, the grain survival rate is 99%. .5% or more, especially 100%, and the grain dropout area ratio is extremely small, 0.5% or less, especially 0.

(2) Specific Effects of the Invention The magnetic head of the present invention is particularly used for magnetic recording, reproduction, erasing, etc. of information on a floppy disk.

1. The core of the magnetic head of the present invention contains 52 to 53 mol % of Fe2O and 17 to 1 mol % of ZnO, as described in detail below.
0.02% by weight or less of silicon oxide and/or 0.02% by weight of calcium oxide relative to the zinc-based ferrite containing 9% by mole.
08fi amount% or less, and if necessary, niobium oxide is added to 0.
．． The material contains 0.02% by weight or less, and has an average grain diameter of 80 μm or less.

Therefore, the obtained magnetic head has a large grain boundary strength of the front core grains, and also has a large initial magnetic permeability and maximum magnetic flux density in the high frequency range of 50 to 300 KHz.
It has extremely excellent magnetic properties with low magnetic loss.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

(Example 1) Fe2O3, ZnO and M shown in Table 1 below
To the composition of n 2 O, powders of silicon oxide, calcium oxide, and niobium oxide were further added in the proportions shown in Table 1, mixed well, and then calcined at 850° C. for 120 minutes.

Next, after pulverizing this calcined product, a small amount of polyvinyl alcohol was added as a binder to form a compacted powder, and the powder was pulverized at 1250 °C in a mixed atmosphere of 2% by volume of oxygen and 98% by volume of nitrogen.
Heated at ˜1350° C. to 96-98% of theoretical density. Next, use a hot isostatic pressure device.

It was sintered at 1000 Kg/cm' and 1200°C until it reached the theoretical density.

Note that the primary firing temperature was varied between 1250 and 1350°C in order to vary the average grain size.

The results are shown in Table 1.

From the ferrite thus obtained, a magnetic path length of 5 mm and a thickness of 0.2 mm was obtained according to a conventional method.

A core with a gap of 0.002 mm was produced. Then, a head was manufactured by attaching a slider and providing a winding.

The following properties were measured for these samples.

(Strength of grain boundaries (%)) Etch the core sliding surface with a 25% hydrofluoric acid aqueous solution (for 2 minutes at room temperature), and after etching, use an optical microscope (40
The area of the grains that fell off was calculated in an arbitrarily extracted field of 6 cm x 9 cm, and the grain remaining area ratio (%) was calculated as the intensity.

(2) Bls Magnetic flux density B 15 (G) at 40℃, DC, 150Oe
was measured.

(3)'to.

40℃, O-, 5mA (7) Initial permeability 100KH
Measured at z.

From the results in Table 1, the effects of the present invention are clear.

In addition, in sample No. 1, 20°C and 60°C
The values of pot and B15 at 0G were measured at 0G.However, the values of pot and B15 at 20℃ are each 11000.4300G, and on the other hand, the values of pot and B15 at 60℃ are 12500.350, respectively.
It was 0G.

Claims (5)

[Claims] (1) 52 to 53 mol% of Fe_2O_3, 1 of ZnO
A material containing 0.02% by weight or less of silicon oxide and/or 0.08% by weight or less of calcium oxide with respect to manganese-zinc ferrite containing 7 to 19 mol%, with an average grain diameter of 80 μm or less. Yes, 40℃,
A magnetic head characterized in that it has a core with an initial magnetic permeability of 8000 or more at 100 KHz and is used at a recording frequency of 50 to 300 KHz. (2) The magnetic head according to claim 1, wherein the core density is 99.5% or more of the theoretical density. (3) The magnetic flux density of the core at 40℃, DC, 15Oe is 4
The magnetic head according to claim 1 or 2, which has a power of 500G or more. (4) When etched for 2 minutes at room temperature with a 25% hydrofluoric acid aqueous solution, the grain dropout area ratio of the core sliding surface is 0.
．． The magnetic head according to any one of claims 1 to 3, wherein the magnetic head has a content of 5% or less. (5) 52 to 53 mol% of Fe_2O_3, 1 of ZnO
A material containing 0.02% by weight or less of silicon oxide and/or 0.08% by weight or less of calcium oxide, and 0.02% by weight or less of niobium oxide with respect to manganese-zinc ferrite containing 7 to 19% by mole. and the average grain diameter is 80 μm or less, 40 ° C., 100 KHz
1. A magnetic head having a core having an initial magnetic permeability of 8000 or more, and used at a recording frequency of 50 to 300 KHz.