Single domain growth and charge ordering of epitaxial YbFe2O4 films

YbFe2O4 is a charge-ordered ferroelectric that exhibits coupling between magnetization and electric polarization near room temperature and crystallizes in a rhombohedral structure (R3¯m). This study presents an attempt to fabricate stoichiometric and epitaxial YbFe2O4-δ films with a nearly single-domain structure using an RF magnetron sputtering method. The (0001)-oriented epitaxial films of YbFe2O4-δ on YSZ (111) substrates via reactive sputtering method exhibited clear three-fold symmetry normal to the substrate without the formation of twin domains rotated by 60°. The oxygen stoichiometry of the epitaxial YbFe2O4-δ was improved by controlling an oxygen partial pressure (PO2) during the deposition. The films showed a sharp ferrimagnetic transition, and the transition temperature (TN) increased linearly to approximately 245 K with decreasing PO2. The magnitude of magnetization of the obtained films was comparable to that of bulk single crystals. Further, the electron diffraction pattern of the stoichiometric films confirmed the presence of three-dimensional charge order, which is consistent with the behavior of the bulk crystals as well.