LAUSR

A series of perovskite materials (BaMnO3−δ and Ba1−xSrxMnO3) were synthesized by a solid-state reaction method. The content of oxygen vacancy can be controlled by verifying the sintering temperature and atmosphere. Two obvious divarications between zero-field-cooling curves and field-cooling curves were observed in a high-temperature region of 250–300 K and at a low temperature of 40 K, respectively. It is found that the different oxygen vacancy contents in BaMnO3−δ cause the change of crystalline structure and variation of the divarication temperature at a high-temperature region. The factor that controls the negative magnetic susceptibility was discussed. The superexchange interaction between Mn ions can give rise to the coexistence of the ferromagnetic phase and antiferromagnetic phase in the system. We further performed the study of magnetocaloric effect in Sr-doped BaMnO3. However, the values of magnetic entropy change and refrigeration coefficient are much smaller than those of rare-earth manganites due to the weak magnetocrystalline anisotropy in Ba1−xSrxMnO3.