晶粒尺寸对Bi_(0.2)Ca_(0.8)MnO_3电荷有序的影响

Grain size effect of charge ordering of Bi_(0.2)Ca_(0.8)MnO_3

利用溶胶-凝胶法制备了平均晶粒尺寸在38—1500 nm的系列Bi0.2Ca0.8MnO3多晶样品,研究了它们的结构、电输运性质和磁性.研究结果表明,随着晶粒尺寸的减小,电荷有序逐渐消失、最后被完全压制,导致低温下出现自旋玻璃态.利用马氏体相变图像和表面效应解释了相关现象.

A series of Bi0.2Ca0.8MnO3 samples with average grain size ranging from 38 to 1500 nm have been prepared by the sol-gel method and their structure,electrical transport,and magnetic properties were investigated.It is found that with the reduction of the grain size,the charge ordered phase gradually diminishes till it is completely suppressed,leading to appearance of the spinglass state at low temperature.These behaviors are discussed in terms of the martensitic transformation and surface effect.