Tuning the polarization and magnetism in BiCoO3 by strain and oxygen vacancy effect: A first-principle study

Abstract

The tensile strain and oxygen vacancy effects on the electronic and magnetic properties of multiferroic material BiCoO3 have been studied by density functional theory + U calculations. It is found that the oxygen vacancy at the top of the pyramid structure along the 〈001〉 direction (denoted as O1) can be stabilized at 1+ and 2+ charge states, which significantly changes the local magnetic moment of Co ions and possibly provides net magnetic moments to the BiCoO3 system. While the tensile strain degrades the polarization of BiCoO3 about 20 μC/cm2, the formation of oxygen vacancies becomes easier as the strain increases up to 5%. It indicates that the polarization and magnetic property of BiCoO3 could be tuned by the strain and oxygen vacancies, though the polarization of BiCoO3 is slightly degraded by the oxygen vacancies. Meanwhile, the change of electronic structure and magnetic property introduced by oxygen vacancy is illustrated according to the crystal field theory.