KCrF_3: Electronic Structure, Magnetic and Orbital Ordering from First Principles

TL;DR

This study uses first-principles calculations to explore the electronic, magnetic, and orbital properties of KCrF_3 across different phases, revealing Mott insulating behavior, orbital order, and potential for charge carrier mobility.

Contribution

It provides a comprehensive first-principles analysis of KCrF_3's phases, detailing their electronic structure, magnetic order, and orbital configurations, which was previously not fully characterized.

Findings

Cubic phase is metallic in LSDA but Mott insulator in LSDA+U with a 1.72 eV gap.

Tetragonal and monoclinic phases exhibit Jahn-Teller distortions and orbital order.

These phases show A-type magnetic order with a bandgap of 2.48 eV.

Abstract

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 is metallic within the LSDA, but at the LSDA+U level it is a Mott insulator with a gap of 1.72 eV. 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 of 2.1 eV, 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.