Abstract: A process for the preparation of cobalt-containing isotropic magnetic iron oxides which are based on gamma-iron(III) oxide, contain from 2 to 7% by weight of cobalt(II) ions and less than 2% by weight of Fe(II) ions, the percentages in each case being based on the iron oxide, and have a particle length of from 0.08 to 0.30 .mu.m, a length/width ratio of from 1.5 to 3.5:1 and a specific remanent magnetization after saturation of not less than 60 nTm.sup.3 /g.

Abstract: A process for the preparation of finely divided ferrites of the general formulaMeFe.sub.2 O.sub.4 (I)where Me=aMn+bNi+cZn+dCo+eFe(II), and the atomic weight ratios a, b, c, d and e are each from 0 to 1 and their sum is 1, orM.sub.2.sup.1 Me.sub.2.sup.1 Fe.sub.12 O.sub.22 (II)where M.sup.1 is barium, strontium, calcium and/or lead, and Me.sup.1 is divalent manganese, copper, iron, cobalt, nickel, zinc, magnesium and/or equimolar amounts of lithium and trivalent iron, orM.sup.2 (Me.sup.2 Ti).sub.x Fe.sub.12-2x O.sub.19 (III)where M.sup.2 is barium or strontium, Me.sup.2 is zinc, nickel and/or cobalt and x is from 0 to 1.5, wherein the aqueous solutions of the salts required for the particular composition are reacted with an aqueous solution of sodium carbonate and/or potassium carbonate, the water is removed, the dry salt mixture is heated at from 800.degree. to 1200.degree. C., and the resulting finely divided ferrite of the predetermined composition is isolated by leaching with water.

Abstract: Magnetic recording media possess, on a dimensionally stable base which may or may not be provided with a non-magnetic lower layer, a thin ferromagnetic metal layer on which a protective layer consisting of a silicon monoxide/chromium dual coating is applied.