Oxygen vacancy effects on double perovskite Bi2FeMnO6: A first-principles study Ayana Ghosh, Towfiq Ahmed, Dzmitry A. Yarotski, Serge M. Nakhmanson and Jian-Xin Zhu EPL, 116 5 (2016) 57002 Published online: 20 January 2017 DOI: 10.1209/0295-5075/116/57002