Single domain growth and charge ordering of epitaxial YbFe2O4 films

YbFe<INF>2</INF>O<INF>4</INF> is a charge-ordered ferroelectric that exhibits coupling between magnetization and electric polarization near room temperature and crystallizes in a rhombohedral structure (R3m). This study presents an attempt to fabricate stoichiometric and epitaxial YbFe<INF>2</INF>O<INF>4-delta</INF> films with a nearly single-domain structure using an RF magnetron sputtering method. The (0001)-oriented epitaxial films of YbFe<INF>2</INF>O<INF>4-delta</INF> 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 degrees. The oxygen stoichiometry of the epitaxial YbFe<INF>2</INF>O<INF>4-delta</INF> was improved by controlling an oxygen partial pressure (P<INF>O<INF>2</INF></INF>) during the deposition. The films showed a sharp ferrimagnetic transition, and the transition temperature (T<INF>N</INF>) increased linearly to approximately 245 K with decreasing P<INF>O<INF>2</INF></INF>. 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.