Magnetic recording material of chromium di:oxide type - having iron oxide coating obtd. by oxidn. of ferrous hydroxide pptd. under reducing conditions

Magnetic recording material has a non-magnetic substrate with a firmly adhering magnetic coating of acicular ferromagnetic CrO2 finely dispersed in an organic polymeric binder and additives. Before incorporation in the binder, the CrO2 is suspended in an aq. soln. of the Fe(II) salt and a reducing agent, the Fe)II) ions are pptd. on the CrO2 as Fe(OH)2 by addn. of water-soluble hydroxide or carbonate and this Fe(OH)2 is then converted to an oxide deposit contg. Fe(III) by treatment with a gaseous or water-miscible oxidant. The oxide deposit pref. consists of goethite and/or lepidocrocite or magnetite. The Fe oxide deposit improves the stability and mechanical properties of the CrO2 under unfavourable climatic conditions.