Orbital correlations in the ferromagnetic half-metal CrO₂

We deduce a model relevant for the description of the ferromagnetic half-metal chromium dioxide (CrO₂), widely used in magnetic recording technology. The model describes the effect of dynamical, local orbital correlations arising from local quantum chemistry of the material. A finite-temperature solution of the model in d=∞ provides a natural explanation of the optical response, photoemission, resistivity, and the large Woods-Saxon ratio observed in experiments. Our study confirms the important role of many-body dynamical correlation effects for a proper understanding of the metallic phase of CrO₂.