Controllable Ground Magnetic States and Exchange Bias in LaMnO₃ Thin Films by the Design of Stoichiometry Offset

Stoichiometry offset provides a promising platform for achieving multifunctionality in perovskite transition metal oxide. In this work, the electric transport and magnetic properties of LaMnO₃ (LMO) films featured with varied stoichiometry offset are systematically investigated. By applying a postannealing process with various annealing oxygen pressures, the concentration ratio of the cation and anion can be tuned, and the magnetic ground states such as ferromagnetic (FM) metal and FM or antiferromagnetic (AFM) insulator of LMO can be obtained. Additionally, a large exchange bias was also observed by an appropriate stoichiometry control. These phenomena can be understood by the regulable magnetic coupling of the Mn³⁺/Mn⁴⁺ and the magnetic phase separation. Our results provide a simple way for achieving stoichiometry offset and a reference for the fundamental understanding of the multiphase coexistence of manganese oxide thin films.