Mn_5Ge_(3-x)Cu_x系列化合物的结构和二级相变特性

Structure and Second Order Phase Transition of Mn_5Ge_(3-x)Cu_x(x=0.0-0.2)Series Compounds

采用流动氩气电弧熔炼和高温退火法,制备了Mn5Ge3-xCux(x=0.0-0.2)化合物,并用粉末X-射线衍射研究了该系列化合物的晶体结构.结果表明:这些化合物都具有Mn5Si3型六角结构,空间群为P63/mcm;Cu对Ge的替代不改变化合物的晶体结构;晶格常数a和晶胞体积V随着Cu含量的增加而增加,而晶格常数c略微减小.用Lakeshore 7407型振动样品磁强计对每个化合物在低场(0.05T)下进行热磁测量,确定了居里温度和磁相变.结果表明,随着Cu含量的增加,化合物的居里温度几乎不变,其磁相变属于铁磁-顺磁二级相变.

The Mn5 Ge3-xCux（x=0.0-0.2）compounds are prepared by means of flowing arc melting and high temperature quenching.The Crystal structure of the compounds has been investigated by means of X—ray diffractometer.The random power X—ray diffraction patterns show that all samples of the com—pounds crystallize in the Mn5 Ge3 type hexagonal structure with space group P63/mcm.Substitution of Cu for Ge does not lead to a change for crystal structure.The lattice parameter a and unit—cell volume monot—onously increases slightly with increasing Cu content,while the lattice parameter c decrease slightly.The magnetic measurement performed with Lakeshore 7407 type vibrating sample magnetomer.The results of the curves show that the Curie temperature TC have no change increasing with Cu content,and show that the magnetic phase transition belongs to second order transition.