Transport, optical and electronic properties of the half metal CrO2

TL;DR

This paper analyzes the electronic, optical, and transport properties of CrO2, revealing moderate many-body effects, deviations from Drude behavior, and the influence of spin fluctuations, with implications for understanding half-metallic ferromagnets.

Contribution

It provides a comprehensive comparison of experimental data with LSDA and GGA calculations, highlighting the sensitivity of mass renormalization to the exchange-correlation functional used.

Findings

Moderate many-body effects observed

Deviations from Drude behavior in optical conductivity

Electron-magnon scattering affects resistivity and spectra

Abstract

The electronic structure of CrO_2 is critically discussed in terms of the relation of existing experimental data and well converged LSDA and GGA calculations of the electronic structure and transport properties of this half metal magnet, with a particular emphasis on optical properties. We find only moderate manifestations of many body effects. Renormalization of the density of states is not large and is in the typical for transition metals range. We find substantial deviations from Drude behavior in the far-infrared optical conductivity. These appear because of the unusually low energy of interband optical transitions. The calculated mass renormalization is found to be rather sensitive to the exchange-correlation functional used and varies from 10% (LSDA) to 90% (GGA), using the latest specific heat data. We also find that dressing of the electrons by spin fluctuations, because of their high energy, renormalizes the interband optical transition at as high as 4 eV by about 20%. Although we find no clear indications of strong correlations of the Hubbard type, strong electron-magnon scattering related to the half metallic band structure is present and this leads to a nontrivial temperature dependence of the resistivity and some renormalization of the electron spectra.