Stabilization of Charge Ordering by Magnetic Exchange

The magnetic exchange energies in charge ordered La$_{1/3}$Sr$_{2/3}$FeO$_{3}$ (LSFO) and its parent compound LaFeO$_{3}$ (LFO) have been determined by inelastic neutron scattering. In LSFO, the measured ratio of ferromagnetic exchange between Fe$^{3+}$-Fe$^{5+}$ pairs ($J_{F})$ and antiferromagnetic exchange between Fe$^{3+}$-Fe$^{3+}$ pairs ($J_{AF})$ fulfills the criterion for charge ordering driven by magnetic interactions ($J_{F}/J_{AF} \quad >$ 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.