JPS6350289B

1. Thermally stabilized ferrimagnetic iron oxides with coercive field strengths of 2.78-3.98 x 10**4 A/M which, upon incorporation into a magnetic tape show an improvement of at least 6 dB in the ratio of the recording level at a frequency of 10 K c/s to background noise according to DIN 45405 in relation to the reference tape according to DIN 45513, section 6/1976, obtainable by dehydrating, tempering and reducing needle-shaped alpha-FeOOH, which has been obtained, at a pH value of below 7, by precipitation from iron (II) salt solutions and oxidation, to iron oxide, the oxidation being terminated on reaching a pH value below 4, characterized in that the alpha-FeOOH has a crystallite size of from 12-22 mm before dehydration and is protected against sintering by chemical stabilization, and in that it contains 0.1-5 % by weight of Cd, Pb, Ca, Mg, Zn, Al, Cr, W, P (expressed as P2 O5 ) and/or B (expressed as B2 O3 ), based on Fe3 O4 .