Antisymmetric double exchange in valence-delocalized [Fe 2.5+ Fe 2.5+] cluster

Abstract

The model of antisymmetric double exchange (DE) interaction is considered for the valence-delocalized [Fe 2.5+ Fe 2.5+] clusters, in which strong Anderson–Hasegawa DE and Heisenberg exchange form the DE states and results in isotropic delocalized ground state Φ − 0( S=9/2) with maximal total spin S. Antisymmetric DE interaction originates from the combined effect of the spin–orbit coupling and DE between the excited and ground states of the Fe ions. The antisymmetric DE coupling admixes the excited DE states Φ + 0(9/2) and Φ − 0(7/2) to the ground delocalized Φ − 0(9/2) state. In the valence-delocalized cluster, the antisymmetric DE coupling is stronger than the Dzialoshinsky–Moriya antisymmetric exchange. The admixture of the excited DE states to the ground delocalized state by the antisymmetric DE coupling and Dzialoshinsky–Moriya exchange results in the spin canting, anisotropy of the hyperfine fields on the Fe nuclei and hyperfine constants, contributes to ZFS.