Abstract: Particulate magnetic oxide compositions based on iron oxide (III) and oxide of at least one bivalent metal selected among cobalt, iron, copper, zinc, magnesium, nickel, manganese and cadmium, characterized in that said compositions contain additionally in the form of an oxide from 0.2 to 5% by weight calculated on the total weight at least one additive or substituent selected among alkali metals, alkaline-earth metals, boron, the elements of columns 3, 4 and 5 of the periodical classification of elements having a molecular mass higher than 26, the transition metals 3d and 4d other than those already mentioned, and the rare earths, with the proviso that when an alkali metal or tin is present, at least another additive or substituent is also present, and in that said compositions have a structure of the lanucar spinel type; the preparation and application thereof are also disclosed.

Abstract: The disclosed particulate composition of simple or mixed oxalate of ferromagnetic metals is characterized in that it is provided in the form of needle-shaped particles having a length comprised between 0.05 and 0.5 micrometer, with a proportion higher than 60% of particles having a length equal to the average length .+-.0.1 .mu.m. and an acicular ratio higher than 3, said average length being comprised between 0.15 and 0.35 .mu.m; its preparation and its application are also disclosed.