JPS6092446A - Magnetic body of metallic iron containing cobalt atom - Google Patents

Abstract

PURPOSE:To obtain a magnetic body maintaining its high saturation magnetization and having improved corrosion resistance by specifying the Co atom content of the titled magnetic body and the ratio of electron intensity of Co2p to that of Fe2p measured by X-ray photoelectric spectrophotometry. CONSTITUTION:This magnetic body of metallic iron contains Co atoms by <=5% of the amount of Fe so that the ratio of the electron intensity of Co2p to that of Fe2p measured by X-ray photoelectric spectrophotometry is adjusted to 0.1- 0.5. Fine powder of alpha-Fe2O3, alpha-FeOOH or the like having <=about 1mum particle size is dispersed in an aqueous soln. contg. a Co salt, and an aqueous soln. of an alkali such as NaOH is added to the dispersion to deposit Co hydroxide on the surface of the powder. The resulting powder is reduced under heating in a reducing atmosphere of H2 or the like. Thus, said magnetic body is easily obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improvement in preventing deterioration of the magnetic properties of a metal ferromagnetic material, and aims to provide a metal ferromagnetic material that is effective for producing a magnetic recording medium that is stable over a long period of time. I'm going to do it.

As magnetic recording equipment becomes smaller and lighter in size, magnetic recording media are required to have improved performance characteristics such as high density recording characteristics, high output characteristics, and high frequency characteristics. The characteristics of the magnetic material to satisfy the requirements are that it has a high coercive force He and a large saturation magnetization I8. A metal iron magnetic material is a magnetic material that satisfies this requirement. However, since metallic iron magnetic materials are very active, they easily generate and accelerate oxidation, corrosion, and iron oxide rust.
There is a drawback that characteristics such as e and #s deteriorate. In order to suppress the occurrence of rust and improve corrosion resistance, there are two methods for K: forming an iron oxide film with a thickness of 2 to 5 μm on the surface of the metal ferromagnetic material, and adding Co uniformly inside the metal ferromagnetic material. be. However, in the former method, a dense oxide film is not formed, so oxygen ions diffuse through the oxide film and react with the internal Fe component to form an oxide, resulting in a decrease in eB in a short period of time. Therefore, it is not considered to be an effective means of preventing deterioration of magnetic properties. If Co is added uniformly into a metal ferromagnetic body, the corrosion resistance is 20~20% higher than that of the metal ferromagnetic body obtained by the former method. However, in order to obtain sufficient corrosion resistance, it is necessary to add a large amount of Co, which results in a decrease in -8, making it difficult to obtain the desired high output characteristics.

The present invention has been made in view of the above circumstances, and aims to provide a magnetic material that maintains the high rigidity of a metal iron magnetic material and has improved corrosion resistance.

In other words, the content of Co atoms in the metallic iron magnetic material should be 5 or less with respect to Fe.9. C by X-ray photoelectron spectroscopy
o The ratio of gP electron intensity to Fetp electron intensity is 0.1 to
By containing s Co in the range of 0.7, it maintains a higher σS and has improved corrosion resistance compared to conventional metallic iron magnetic materials.@According to the present invention, s Co
Since the content of o atoms is only small, less than jffi1f1% of Fe, the high level of the metal ferromagnetic material is maintained, and Co atoms are mainly contained in the surface layer of the metal ferromagnetic material. Therefore, a dense anti-oxidation film is formed by Co, Fe, metals, or their oxides, and exhibits good corrosion resistance.

The composition of Co and Fe in the surface layer of the magnetic material according to the present invention can be easily determined by Xm photoelectron spectroscopy, as is commonly known.
, Corp electron intensity by molecular spectrometry and FaxI)'
It is obtained by setting the Ftl color strength to 0.1 or more, and as this ratio increases, the corrosion resistance improves. However, when this ratio exceeds 0.7, the content of Co atoms exceeds 5 M% with respect to Fe, and 18 is lower than that of the conventional one. is preferably added within 5 weight nt%.

The magnetic material according to the present invention is (1-FegOa 1 (1-
Fine iron oxide or iron oxyhydroxide powder such as Fe00H with a particle size of 1 μm or less is dispersed in an aqueous solution containing cobalt salt, and an aqueous alkaline solution such as NaOH or KOH is added to the iron oxide or iron oxyhydroxide powder. It can be easily produced by precipitating cobalt hydroxide on the surface of the compound and then reducing it by heating in a reducing atmosphere such as in hydrogen.

Further, the magnetic material according to the present invention is effective as a recording element of a magnetic recording medium, but when used as this recording element, a needle-like material with a grain size of 1 μ or less and an axial ratio of 2 or less is usually used as follows. This is suitable for obtaining desired electromagnetic conversion characteristics.

Examples of the present invention will be described below.

Example 1 After dissolving a cobalt salt corresponding to the amount of Co shown in Table 1 in the aqueous solution of 11 for Fe of α-Felon,
α-Fo*O* 150 f is dispersed, and NaO
Add KOII aqueous solution and age at 40 to 90° to form a cobalt hydroxide film on the surface of α-Fezes. In order to prevent the magnetic material from deforming or sintering during hydrogen reduction, perform the following operations: FJII α-Fe*O treated with k
s is dispersed, and a NaOH or KOH aqueous solution is added to the solution to make the pH higher than 11, and the Si hydroxide is deposited on the surface of the α-Fezes treated above. After that, it is thoroughly washed with water and dried at 121) °C. After drying, put it in a quartz boat and keep it at a temperature of 350 to 500℃, and keep it at a temperature of 0.2 to 0.5
Reducing in a tube furnace while aerating hydrogen at a flow rate of 17 minutes◇
After reduction, the toluene solvent was slowly cooled, air was blown into the toluene solvent for 10 minutes, and the mixture was air-dried.

Table 1 Comparative Examples 1 and 5 cobalt salt loading amounts How much cobalt oxide was added so as to contain 5% by weight in terms of Co to the Fe in the sulfur-free ferrous water bath solution of 5 wol/l, NaO, I) H12-13 using H aqueous solution
About 5 Co atoms were obtained by air oxidation at a temperature of 50°C and an air flow rate of 451/min.
Acicular crystals α-Feα) If containing uniformly 600
C. to form α-Fee's. Next, silicate was added to Fe (7 to 3 times), α-1i”etOs was dispersed in an aqueous solution of I”c 11, Na(M[a) or KO)l water bath solution was added, and pI (11, II on top, S
In order to settle the hydroxide of i, wash thoroughly with water and add 120
Dry at 0°C. Place this in a quartz boat and heat at 350-50°C.
0 temperature and reduce while passing hydrogen at a flow rate of 0.2 to 0.51/fJ- ◇ After the reduction, the sample is slowly cooled, and then immersed in a toluene solvent for 10 minutes while blowing air and air-dried.

The magnetic materials obtained in the above Examples and Comparative Examples were measured for pieces containing Co atoms and Fe atoms by atomic absorption spectrometry,
In addition, the magnetic materials obtained in the above Examples and Comparative Examples were analyzed using X-ray TLT molecular spectroscopy with a diameter of 1Q mm, a height of Q, and a height of 5 m.
The intensity ratio of Coxp electrons and F911P electrons within a depth of about 2 mtn from the surface of a sample molded into a disk of m was measured.

Corrosion resistance is #S immediately after manufacture and 80%RH for one week after manufacture.
The σ8 after storage at 60°C was measured, and the deterioration rate from 118 immediately after production was calculated.90 From the above results, the comparative example containing Co atoms uniformly had good corrosion resistance but had a low d8. In comparison, samples 2 to 4 of implementation row 1 according to the present invention have high IFB
It is clear that the material maintains good puncture resistance and exhibits good puncture resistance.

Applicant: Hitachi Maxell, Ltd. Representative Atsushi Nagai

Claims (1)

[Claims] The content of Co atoms is 5% or less with respect to Fe, and the ratio of Co2p electron intensity to Fe2p electron intensity by X-ray photoelectron spectroscopy is in the range of 0.1 to 0.5.
Metallic iron magnetic material containing atoms◎