Gd^(3+)掺杂对Sr_2FeMoO_6结构及电磁性能的影响

Effect of Gd^(3+) doping on phase structure,magnetic and electrical properties of double perovskite Sr_2FeMoO_6

采用微波固相烧结法合成了双钙钛矿Sr2-xGdxFeMoO6(x=0.0、0.1、0.2、0.3)。用XRD和VSM对样品的物相结构和电磁性能进行了研究。结果表明所得Sr2FeMoO6为四方晶系结构,空间群为I4/mmm,随Gd3+掺杂量的增加,Fe、Mo排列的有序度逐渐降低,同时伴有少量Gd2O3杂相生成。样品Sr2-xGdxFeMoO6均表现为铁磁性,磁转变温度均高于室温,Gd3+掺杂使得样品的室温饱和磁化强度降低,但适量Gd3+的掺杂(x=0.3)可明显提高样品的室温磁电阻变化率。样品Sr2-xGdxFeMoO6均呈现典型的半导体行为,当x=0.0、0.1、0.2时,在100～300K,其电输运行为服从小极化子变程跃迁导电机制;当x=0.3时,在150～300K,服从小极化子变程跃迁导电机制;在100～150K,则属于绝热小极化子导电机制。

Double perovskite Sr2-xGdxFeMoO6（x=0.0,0.1,0.2,0.3） were synthesized by microwave sintering method.The phase structure,magnetic and electrical properties of all the samples were investigated by X-ray powder diffraction（XRD） and vibrating-sample magnetometer（VSM） respectively.The results show that the as-synthesized sample is Sr2FeMoO6 with tetragonal crystal structure and I4/mmm space group.With the increase of doped Gd3＋,the ordering degree of the Fe and Mo cations decreases gradually,accompanied by a small amount of impurity phase Gd2O3.The samples Sr2-xGdxFeMoO6 are ferromagnetic,and the magnetic transition temperature is above room temperature.The saturation magnetization is decreased with the doping of Gd3＋ at room temperature,but magnetoresistance ratio can be improved significantly when the doping concernt of Gd3＋ x=0.3.The samples Sr2-xGdxFeMoO6 exhibit typical semiconductor behavior.When x=0.0,0.1,0.2,the electrical transport behavior follows the small polaron variable-range transition model in the range of 100-300K.When x=0.3,it follows the small polaron variable-range transition model in the range of 150-300K;but it is ascribed to the adiabatic small polaron conduction mechanism in the range of 100-150K.