KCrF3: Electronic structure and magnetic and orbital ordering from first principles

The electronic, magnetic and orbital structures of KCrF3 are determined in all its recently identified crystallographic phases (cubic, tetragonal, and monoclinic) with a set of ab initio local spin density approximation (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 KCrF3 exhibit cooperative Jahn-Teller distortions concomitant with staggered 3x2−r2/3y2−r2 orbital order. We find that the energy gains due to the Jahn-Teller distortion are 82 and 104 meV per chromium ion in the tetragonal and monoclinic phases, respectively. These phases show A-type magnetic ordering and have a band gap of 2.48 eV. In this Mott insulating state, KCrF3 has a substantial conduction bandwidth leading to the possibility for the kinetic energy of charge carriers in electron- or hole-doped derivatives of KCrF3 to overcome the polaron localization at low temperatures, in analogy with the situation encountered in the colossal magnetoresistive manganites.