Temperature dependent exchange bias effect in polycrystalline BiFeO3/FM (FM = NiFe, Co) bilayers Xiaobo Xue, Xueyong Yuan, Wenbin Rui, Qingyu Xu, Biao You, Wei Zhang, Shiming Zhou and Jun Du Eur. Phys. J. B, 86 4 (2013) 121 Published online: 27 March 2013 DOI: 10.1140/epjb/e2013-31003-y