Manipulating multiple order parameters via oxygen vacancies: The case of Eu0.5Ba0.5TiO3-δ

Controlling functionalities, such as magnetism or ferroelectricity, by means of oxygen vacancies (V-O) is a key issue for the future development of transition-metal oxides. Progress in this field is currently addressed through V-O variations and their impact on mainly one order parameter. Here we reveal a mechanism for tuning bothmagnetism and ferroelectricity simultaneously by using V-O. Combining experimental and density-functional theory studies of Eu0.5Ba0.5TiO3-delta , we demonstrate that oxygen vacancies create Ti3+ 3d(1) defect states, mediating the ferromagnetic coupling between the localized Eu 4f(7) spins, and increase an off-center displacement of Ti ions, enhancing the ferroelectric Curie temperature. The dual function of Ti sites also promises a magnetoelectric coupling in the Eu0.5Ba0.5TiO3-delta.