Single domain growth and charge ordering of epitaxial YbFe₂O₄films

YbFe₂O₄is a charge-ordered ferroelectric that exhibits coupling between magnetization and electric polarization near room temperature and crystallizes in a rhombohedral structure (R3̄m). This study presents an attempt to fabricate stoichiometric and epitaxial YbFe₂O_4−δfilms with a nearly single-domain structure using an RF magnetron sputtering method. The (0001)-oriented epitaxial films of YbFe₂O_4−δon YSZ (111) substratesviareactive 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 YbFe₂O_4−δwas improved by controlling an oxygen partial pressure (P_O2) during the deposition. The films showed a sharp ferrimagnetic transition, and the transition temperature (T_N) increased linearly to approximately 245 K with decreasingP_O2. 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.