Production of magnetic powder

Claim 1

Acicular iron particles having improved properties for magnetic recording which contain at least one metal selected from the group consisting of zinc, chromium and copper, produced in accordance with the process comprising (a) treating a finely divided starting material in the form of acicular micro-particles selected from the group consisting of (i) iron oxyhydroxide, (ii) iron oxhydroxide containing a doping component selected from Co, Mn, Ni, Ti, Bi, Mo, Ag, Cr, Zn, Si, Al and mixtures thereof, (iii) iron oxides and (iv) iron oxides containing a doping component selected from Co, Mn, Ti, Bi, Mo, Ag, Cr, Zn, Si, Al and mixtures thereof, with an aqueous (1) solution or (2) suspension of an applied metal compound selected from the group consisting of zinc, chromium and copper compounds and mixtures thereof or a mixture of said aqueous solution and said aqueous suspension so that said applied metal compound is applied to said starting material, (b) filtering the thus treated material off the liquid medium to form a cake and drying said cake, and (c) reducing said dry cake in a reducing gas stream at a temperature up to about 600° C. whereby the individual particles are not sintered and the initial shape of the micro-particles of the starting material is retained and to form an acicular magnetic iron particle consisting essentially of iron and said applied metal selected from the group consisting of zinc, chromium and copper and mixtures thereof.