Charge ordering of multiferroic LuFe_2O_4: influence of doping and electric field

摘要

A charge ordering of nonstoichiometric LuFe_2O_(4+δ) is discussed. Properties of triangular bilayer are investigated via mean field theory with Coulomb interaction between sites. It is shown that low temperature state of bilayer has a dipole moment essentially under any doping parameter. Correlation between sites in neighboring layers is estimated and dimer partially disordered antiferroelectric phase is extended for the case of nonstoichiometric samples. Competition of correlation effect with bilayer interaction and external electric field is discussed. Phase diagrams for doped specimen are presented. The results of investigation are used to clarify a significant surface impact.