Cooperative Jahn-Teller Distortion,Phase Transitions,and Weak Ferromagnetism in the KCrF_3 Perovskite

摘要

The chemistry of transition-metal oxides has been full of surprises and intriguing structural,electronic,and magnetic phenomena.One of the key ingredients at the origin of these effects is the availability of degenerate electronic orbitals.Whether such orbital degrees-of-freedom actually occur in a material depends on the nature of the atomic ions and the surrounding crystallographic structure.Prominent examples of ions that display active orbital degrees-of-freedom include the Jahn-Teller (JT) Mn~(3+) (d~4) and Cu~(2+) (d~9) ions.