Charge order and the origin of giant magnetocapacitance in LuFe2O4

The nature of the charge order in the charge frustrated compound LuFe2O4 and its effect on magnetocapacitance were examined on the basis of first-principles electronic structure calculations and Monte Carlo simulations of electrostatic energy. Our work shows that two different types of charge order of almost equal stability (i.e., root 3 x root 3 and chain types) occur in the Fe2O4 layers of LuFe2O4, and that the ground state of LuFe2O4 has a ferrielectric arrangement of the Fe2O4 layers with root 3 x root 3 charge order. The giant magnetocapacitance effect of LuFe2O4 at room temperature is accounted for in terms of charge fluctuations arising from the interconversion between the two types of charge order, that becomes hindered by an applied magnetic field.