JPS6011232A - Manufacture of magnetic oxide particle - Google Patents

Abstract

PURPOSE:To manufacture magnetic oxide particles having a uniform particle size, high saturation magnetization, large coercive force and a high squareness ratio by calcining a mixture of one or more kinds of carbonates selected among Ba, Sr, Pb and Ca carbonates with a specified metallic oxide and by carrying out grinding and acid treatment. CONSTITUTION:Carbonates of one or more kinds of metals selected among Ba, Sr, Pb and Ca are mixed with oxides of one or more kinds of metals selected among Cu, Zn, Ni, Co, Mn, Mg and Fe. The mixture is calcined, ground, and treated with an acid to obtain hexagonal ferrite particles contg. a platelike W phase and having 0.1-0.3mum particle size, >=60emu/g saturation magnetization and 600-1,500(Oe) coercive force. When the ferrite particles are used as magnetic particles for a magnetic recording body, high-density vertical magnetic recording can be attained while using a tape formed by coating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing oxide magnetic particles, and in particular to improving the magnetic properties of hexagonal nerite particles exhibiting a W-set type crystal structure, as well as increasing the particle size from 0.1 to 0.1. The aim is to align them to about 0.03 μm.

In recent years, since the advent of magnetic disks, the development of high-density magnetic recording technology has progressed rapidly, and numerous studies have been conducted.

A perpendicular magnetic recording system has been proposed as one of such high-density magnetic recording methods.

In general, the conditions required for a magnetic medium for perpendicular magnetic recording are as follows.

(a) Must have magnetic anisotropy perpendicular to the recording surface.

(b) Must have a certain degree of coercive force.

(c) It is required to have high saturation magnetization.

Some of the inventors of the present invention have proposed a magnetic recording medium using W-type hexagonal ferrite particles as magnetic particles that can satisfy such requirements in Japanese Patent Application No. 57-216658 (Japanese Unexamined Patent Publication No. 1983-1993). .

W-set type hexagonal ferrite particles (hereinafter referred to as W-phase 2 elite) have the general formula n aMe 2 Fe 16027
(However, M- is a divalent metal). The axis of easy magnetization of these ferrite particles is perpendicular to the plate-like surface, so if they are applied to the base teno while magnetically oriented.

Uniaxial anisotropy perpendicular to the tape surface can be achieved.

By the way, since W-phase ferrite is generally fired at a high temperature of 1250° C. or higher, sintering occurs between the powders, resulting in a two-grain size of 5 μm or higher. Therefore, 0.1 to 0.3 μm
In order to obtain a moderately fine powder, it is necessary to undergo a physical pulverization process using a ball mill, vibration mill, etc. As a result 9. Mechanical strain 1. Surface change Superparamagnetization due to ultrafine powder,
Saturation magnetization C due to the influence of impurities from the crusher, etc.
8 coercive force IHC and squareness ratio σr//a8 were disadvantageous.

In view of these points, the object of the present invention is to provide a manufacturing method that can remove the above-mentioned defects by acid treatment such as HCt or H2SO4 without deteriorating the magnetic properties, and can significantly improve σ IHc and squareness. Our goal is to provide the following. Saturation magnetization σ8 is 60 (emu, /gr) or more, IHc is 60
0 (Oe) or more and 1500 (Oe) or less is necessary to obtain a high recording density, and the squareness ratio is proportional to the perpendicular magnetic anisotropy when applied to the tape, so it is necessary to have a large squareness ratio. This is desirable.

The method for producing oxide magnetic particles according to the present invention includes, as starting materials, at least one carbonate of Ba, Sr, Pb, and Ca, and Cu, zn, Ni, Co, Mn.
, Mg and Fe with at least one of oxides is calcined, physically pulverized, and then treated with an acid to obtain plate-like ferrite particles containing a W phase.

Here, the acid treatment removes the factors that deteriorate the magnetic properties and reduces the size of the W-phase ferrite particles by 0.1 to 0.3.
The acid concentration and acid treatment time are such that the thickness is uniform on the order of μm.

Examples of the present invention will be described in detail below.

Example-1 Barium carbonate B a CO3 and iron oxide Fe2O3 were used as starting materials in a 2 molar ratio of BaCO3", Fe2O3
Weigh each so that == 1:9, mix uniformly with a ball mill, and then heat at 1250°C for 5 hours at an oxygen partial pressure of 10.
It was fired in N2 gas at ATM to produce W-type hexagonal ferrite.

After this, the powder was coarsely crushed and sieved, and the powder of -325 methane was crushed together with a steel goal in a ball mill.

Saturation magnetization moment σ8 and coercive force I per unit weight of ferrite particles crushed up to the final crushing time (325 hr)
The squareness ratio σrAI8 of Hc and the powder oriented in a dry magnetic field was measured using a sequential vibration magnetometer. Furthermore, the particle size distribution state was observed using a scanning electron microscope.

In addition, after dissolving these ferrite particles in dilute hydrochloric acid with varying concentrations for 5 minutes, the C8■Hc and squareness ratio σr''a were similarly measured, and the particle size distribution is summarized in Table 1. .

Table 1 W phase 1 gr Time 5 minutes As is clear from Table 1, as the hydrochloric acid concentration increases, σBl
Although IHc and σrA&3 are significantly improved, the improvement is not so great when the solution becomes dilute. In addition, the grain size was 0.05 to 0.7 μm in the ball mill before treatment, and the distribution width was wide, but after acid treatment, the distribution width became smaller, and the W-phase ferrite particles had a uniform rectangular plate shape. was gotten.

As a magnetic medium for perpendicular magnetic recording, C8 is practically 60 (emu/gr) or more, and IHc is 600 (O
It is understood that the effect of acid treatment is large, considering that it is said that it is good that both of e) and above are good. Also, from Table 1, it can be seen that the squareness ratio σ76s has been significantly improved9. The maximum has reached nearly 90%. This means that when these particles are applied to a tape in a magnetic field, it is possible to obtain an angular-swelling ratio greater than that of the tape.

Example-2 Barium carbonate BaCO3 and copper oxide Cub as starting materials
.

Zinc oxide ZnO and iron oxide Fe2O3 in molar ratio Ba
C0: CuO: ZnO: Fe2O3,=1 :o
, s : 12: 8, were mixed uniformly in a ball mill, and then fired in the air at 1250° C. for 1 hour to obtain W-type hexagonal ferrite. Said Example-1
In the same manner as above, it was coarsely ground, sieved, and ground in a ball mill.

The magnetic properties (σB + , IHc rσr/”s) and particle size distribution of ferrite particles crushed until the final crushing time (360 hr) and those dissolved in dilute hydrochloric acid for 5 minutes were measured in the same manner as in Example-1. The results are summarized in Table 2. As is clear from Table 2, as the hydrochloric acid yield increases, σ,
Although p IHc and σr/% are significantly improved, if the thickness is too thin, the improvement is not so great. In addition, the grain size also has less fluctuation due to the acid treatment.

The embodiments of the present invention have been described above using HCl, but H2SO4
This is also possible with acids such as, and also includes acid treatment at elevated temperature.

As is clear from the above examples, according to the method of the present invention, it is possible to obtain W-set hexagonal noelite particles with greatly improved saturation magnetization, coercive force, and squareness ratio.

Therefore, when the ferrite particles obtained according to the present invention are used as magnetic particles for a magnetic recording medium, high-density perpendicular magnetic recording can be achieved with a coated tape.

Claims (1)

[Claims] 1. As starting materials, at least one of carbonates of Ba, Sr+Pb and Ca; Cu, Zn, Nt,
Co+Mn. 1. A method for producing oxide magnetic particles, which comprises obtaining ferrite particles containing a plate-like W phase by firing and physically pulverizing a mixture of Mg and Fe with at least one of oxides, and then subjecting the mixture to acid treatment.