Stabilization of charge ordering in La1/3Sr2/3FeO3-δ by magnetic exchange

The magnetic exchange energies in charge ordered La1/3Sr2/3FeO3-delta (LSFO) and its parent compound LaFeO3 (LFO) have been determined by inelastic neutron scattering. In LSFO, the measured ratio of ferromagnetic exchange between Fe3+-Fe5+ pairs (J(F)) and antiferromagnetic exchange between Fe3+-Fe3+ pairs (J(AF)) fulfills the criterion for charge ordering driven by magnetic interactions (|J(F)/J(AF)|> 1). The 30% reduction of J(AF) as compared to LFO indicates that doped holes are delocalized, and charge ordering occurs without a dominant influence from Coulomb interactions.