Defect engineering of EuTiO₃ epitaxial thin films

Controlling the atomistic defect in perovskite transition metal oxides facilitates tailoring of their emergent functionality, especially in terms of opto-electromagnetic and energy properties. Pulsed laser epitaxy (PLE) offers a deliberate control of the formation of defects in perovskite oxides, leading to a modulation of the charge, spin, lattice, and orbital degrees of freedom, sometimes separately, and in other times collectively. Perovskite EuTiO₃ (ETO) is a promising candidate for studying the strong coupling between the lattice, electronic, and magnetic ground state by introducing defect and/or epitaxial strain, because it exhibits a magneto-electric phase transition from a paraelectric (PE) antiferromagnetic (AFM) to a ferroelectric (FE) ferromagnetic (FM) phase. Here, we systematically induced defects in ETO thin films using PLE. The lattice unit cell (u.c.) volume was modulated by defect engineering, which was closely related to the FM ordering in the thin film. The change in the electronic structure further supported the FM phase with weaken Eu-Ti-Eu superexchange interaction.