CRO2 - A SELF-DOPED DOUBLE EXCHANGE FERROMAGNET

With the help of band structure calculations (LSDA + U) a clear pictur e of the physics behind the metallic ferromagnetic properties of CrO2 is revealed. It is concluded that CrO2 is a negative charge transfer g ap material which leads to self-doping and explains why it is a metal in spite of the large Coulomb interactions. We find that there exist i n CrO2 both localized and itinerant d electrons, resulting in ferromag netic ordering due to double exchange similar to colossal magnetoresis tance manganates.