Transport, optical and electronic properties of the half metal CrO2

The half metal ferromagnet CrO2 has interesting and unusual electronic properties. As in many other cases when kinetic properties are not easily described by the conventional Bloch-Boltzmann theory, strong correlation effects of the Hubbard type were called for explanation of the electronic properties of CrO2. Here we report detailed analysis of the electronic structure and related properties of CrO2, based on state-of-the-art density functional calculations. We conclude that (1) the most current experimental data do not indicate an anomalously large mass renormalization, (2) temperature dependence of the resistivity is due mainly to the scattering by spin fluctuations, (3) coupling between charge (electrons) and spin (magnons) degrees of freedom is anomalously strong, (4) recent optical measurements can be reasonably interpreted within the quasi-one-electron density functional calculations, and (5) their deviation from the experiment is opposite to that expected in the Hubbard model, and agrees with a physical picture of electrons dressed by spin fluctuations. (C) 1999 The American Physical Society. [S0556-2821(99)03904-1].