Surface morphology driven non-uniform magnetism in epitaxial BiMnO3

Abstract

Thin films of BiMnO3 were grown on (001) SrTiO3 substrates by fine tuning the growth conditions. The films are epitaxial and impurity-free, but show island growth mode. From detailed magnetization measurements and surface analysis, we found evidence of morphology driven non-uniform magnetism. The non-uniform magnetism resulted in reduced saturation magnetization, reduced Curie temperature (TC), and nonlinear Arrott plots. In spite of non-uniform magnetism, the temperature dependence of magnetization showed conventional mean field behavior near TC. Our data suggest that non-uniform strain leads to coexistence of separate ferromagnetic and ferroelectric regions in BiMnO3 films which is not observed in bulk samples.