Non-acicular modified high coercivity iron oxides for high densi

Details Non-acicular modified high coercivity iron oxides for high densi Non-acicular modified high coercivity iron oxides for high densi

1991-12-04

1996-01-30

Kilman, L.

Stock material or miscellaneous articles

Composite

Of inorganic material

428694BA, 428694BM, 428900, 423633, 423636, 252 6251, 252 6256, G11B 566, C04B 3500, C01G 4902

Patent

active

054879540

ABSTRACT:
The non-acicular modified maghemite and magnetite have high coercivity of, for the maghemite, up to 2200 Oe, saturation and residual magnetization of 63-85 emu/g and 43-52 emu/g, respectively; for the magnetite, the corresponding values are 800-1600 Oe, 82-87 emu/g, and 44-51 emu/g, respectively; while retaining same squareness ratio and same chemistry with conventional iron oxides, fine particle size of around 50 nm, easier dispersion and coating, invaried properties after curing, and low value of temperature coefficient of coercivity (0.24-0.37%/.degree. C. for the maghemite and 0.20-0.33%/.degree. C. for the magnetite), have been invented. They are thus especially suitable for high density recording. The modified maghemite and magnetite are prepared by precipitating from aqueous solution containing Fe, Mn, Co and Zn ions at proper ratio using an organic alkali as precipitant, followed by specific heat treatment sequences.

REFERENCES:
patent: 3928709 (1975-12-01), Audran et al.
patent: 4015030 (1977-03-01), Sasazawa
patent: 4178387 (1973-12-01), Sasazawa
patent: 4255492 (1981-03-01), Audran et al.
patent: 4323621 (1982-04-01), Kober et al.
C. D. Mee et al. in Magnetic Recording vol. 1, Technology Mc.Graw-Hill, 1987.

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