Exchange bias in BiFeO_3/La_(0.67)Sr_(0.33)MnO_3 bilayers

摘要

The exchange bias in BiFeO_3/La_(0.67)Si_(0.33)MnO_3 (BFO/LSMO) bilayers has been investigated. Exchange bias field with blocking temperature of about 150 K and enhanced coercivity at room temperature has been observed in (001) BFO/LSMO bilayers. The blocking temperature coincides well with the emerging temperature of the vertical magnetization shift due to the blocking of the possible interfacial spin glass. Only enhanced coercivity without exchange bias field down to 10 K has been observed in (111) BFO/LSMO bilayers. The piezoelectric force microscopy images show that the domain size of (111) BFO is 2 orders larger than that of the (001) BFO, indicating the much higher domain wall density in (001) BFO. Our results demonstrate that the exchange coupling with interfacial spin glass at the domain walls contributes to the exchange bias field with blocking temperature of about 150 K, while the exchange coupling with the domains contributes to the enhanced coercivity up to room temperature.