Contrasting effects of mismatch strain on the magnetic behavior of undoped and doped BaFeO3-δ thin films

Abstract

We investigate the effects of biaxial compressive and tensile strain on the magnetic and structural properties of BaFeO3-δ (BFO), BaFe0.9Ti0.1O3-δ (BFTO) and BaFe0.9Ru0.1O3-δ (BFRO) thin films fabricated on SrTiO3 (001) (STO) and MgO (001). The magnetization measurements show a long range ferromagnetic ordering in compressive strained BFO thin film while an antiferromagnetic ordering with weak ferromagnetism appears in tensile strained BFO thin film. This behavior is ascribed to the difference in oxygen stoichiometry under the two strain states in the BFO thin films. Ti4+ (3d0) and Ru4+ (4d5) ion substitutions at B-site cause an increase in unit cell volume irrespective of the strain type resulting in relaxation of tensile strain and enhancement of compressive strain. This B-site disorder leads to collapse of long range ferromagnetic ordering in BFTO and BFRO thin films grown on STO but an increased ferromagnetic ordering comes along in BFTO and BFTRO thin films on MgO. The contrasting results portray that tensile strain suppresses the effect of cation disorder evident under compressive strain, on the magnetic and structural properties of BFO, BFTO and BFRO thin films.