KCrF$_3$: Electronic structure and magnetic and orbital ordering from first principles
Gianluca Giovannetti, Serena Margadonna, and Jeroen van den Brink

The electronic, magnetic and orbital structures of KCrF$_3$ are determined in all its recently identified crystallographic phases (cubic, tetragonal, and monoclinic) with a set of {\it ab initio} LSDA and LSDA+U calculations. The high-temperature undistorted cubic phase appears as a metal from LSDA, but it is a Mott insulator with a gap of 1.72 eV at the LSDA+U level. The tetragonal and monoclinic phases of KCrF$_3$ exhibit cooperative Jahn-Teller distortions concomitant with staggered $3x^2-r^2$/$3y^2-r^2$ orbital order. We find that the energy gain due to the Jahn-Teller distortion is 82/104 meV per chromium ion in the tetragonal/monoclinic phase, respectively. These phases show A-type magnetic ordering and have a bandgap of 2.48 eV. In this Mott insulating state KCrF$_3$ has a substantial conduction bandwidth leading to the possibility for the kinetic energy of charge carriers in electron- or hole-doped derivatives of KCrF$_3$ to overcome the polaron localization at low temperatures, in analogy with the situation encountered in the colossal magnetoresistive manganites.

© 2008 The American Physical Society.