The chemical and physical properties of CrO2and tetravalent chromium oxide derivatives

The oxide of chromium (IV), Cr02, is a highly interesting compound for materials investigation in that it is ferromagnetic at room temperature and a good electrical conductor. The Curie temperature is 118°C, and the material can readily be demagnetized with little energy input. The electrical conductivity of this black compound is quite high for an oxide; it even rivals some of the metal conductors such as Mn and Gd at roomtemperature. Thls review describes procedures for preparing Cr02, presents its chemical and physical properties including the modifications observed with metal-ion substitutions, and discusses the reactions of Cr02 with other metal oxides together with the physical properties of the ternary products containing tetravalent chromium.