Properties of stress-induced super tetragonal phase in epitaxial BiFeO_3 thin film

摘要

Stress-induced structural phase transitions in multiferroic BiFeO_3 thin films have attracted much attention for both fundamental research and promising applications in electronic devices. In this work, with the assistance of spherical aberration-corrected transmission electron microscopy, a tetragonal phase with the super large tetragonality (c/α ~ 1.53) was found in the epitaxial BiFeO_3 thin film on a LaAlO_3/Si substrate. Analyses of atom positions showed that displacements of an Fe atom in this super tetragonal phase are much smaller than that in a regular tetragonal phase. First-principles calculations revealed that the structural phase transition occurs with the increasing lattice tetragonality cla, accompanied by transitions in the atomic coordination and magnetic order.