Novel ferromagnetic chromium dioxide and rhodium dioxide material and

Abstract

Process for making a novel ferromagnetic chromium dioxide and rhodium dioxide material in the form of a solid solution Cr.sub.1-x Rh.sub.x O.sub.2 where x is a number between 0 and 0.5. It essentially comprises oxidation, under suitable conditions of temperature and pressure, of hydrated or anhydrous Cr.sub.2 O.sub.3 or of a precursor of Cr.sub.2 O.sub.3, in the presence of (1) an appropriate amount of a compound of rhodium III able to give RhO.sub.2 under reaction conditions and (2) of an oxidizing agent consisting of an oxygenated compound free from metallic cations other than chromium and having, under the reaction conditions, a partial oxygen pressure at least equal to that corresponding, under the same conditions of temperature and pressure, to the equilibria Cr.sub.2 O.sub.3 +1/2O.sub.2 .revreaction.2CrO.sub.2 and Rh.sub.2 O.sub.3 +1/2O.sub.2 .revreaction.2RhO.sub.2 as well as eventually (3) of dilution water and/or of at least an additional doping agent acting as buffer in the reaction medium and/or a conventional modifying agent. The invention is useful for the manufacture of a ferromagnetic material possessing improved magnetic characteristics.