本文系统地研究了具有电荷有序(CO)和C型反铁磁(AFM)磁结构的钙钛矿锰氧化物Bi0.5Ca0.5-xBaxMnO3(x=0,0.03,0.05,0.07 and 0.10)的结构、磁性和电输运性质.系统晶格对称性保持Pnma空间群正交结构不变.随着Ba掺杂浓度的提高,电荷有序转变温度和反铁磁转变温度明显降低,表明掺杂导致的带宽增大使得电荷有序减弱.在电荷有序转变之前,所有样品的电输运行为服从小极化子传导(SPC)机制,而在电荷有序转变之后,则服从Mott可变程跃迁(VRH)机制.
Structure, magnetic and transport properties of Bi0. 5Ca0. 5-xBaxMnO3 (x=0,0.03, 0.05, 0.07 and 0.10) samples with charge ordering (CO) state and C-type antiferromagnetic (AFM) magnetic structure have been studied systematically. All samples have the orthorhombic structure with Pnma space group. With increasing Ba doping level, both CO transition temperature Tco and AFM transition temperature TN shift to lower temperatures,which means that CO weakens due to increasing bandwidth. For all the samples the adiabatic small polaronic conduction (SPC) mechanism is responsible for the transport behavior above CO transition, whereas Mott's variable range hopping mechanism dominates below the CO transition.
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