Ca 掺杂对 SmCoAsO 磁性的影响

摘要

为了探究 SmCoAsO 体系中 Sm 在其磁性中的作用，用 Ca 在 Sm 位进行掺杂。采用固相反应法制备 Sm1-x Cax CoAsO（x＝0，0．05，0．1，0．2），通过 X 射线衍射仪、超导量子干涉仪等对其结构和磁性进行表征。结果表明，制得的 Sm1-x Cax CoAsO 单相性较好，具有四方 ZrCuSiAs 型晶体结构，且 Ca 掺杂对晶格参数的影响很小。Sm1-x Cax CoAsO 在低温下发生了反铁磁、铁磁及亚铁磁多重磁转变，而且在反铁磁转变温度以下，观察到了磁场导致的变磁性转变，且变磁场随温度的升高而降低。Ca 在 Sm位掺杂抑制了 SmCoAsO 的亚铁磁转变，当掺杂量为0．2时，亚铁磁转变温度降低了23 K。因此，在 SmCoAsO 中，Co 的磁矩决定铁磁和反铁磁性，而 Sm 经由在 c 方向上的 Sm-O 层与 Co-As 层之间的相互作用决定亚铁磁性。%In order to investigate the contribution of Sm in SmCoAsO magnetism,Ca-doped SmCoAsO compounds (Sm1-x Cax-CoAsO,x=0,0.05,0.1,0.2)were synthesized by solid-state reaction.The crystal structure was studied by powder X-ray dif-fraction.DC magnetization was measured by a superconducting quantum interference device magnetometer.All samples showed a single phase and can be indexed as a tetragonal ZrCuSiAs type structure,and Ca doping did not change the cell parameters.Com-plicated magnetism consists of antiferromagnetism,ferromagnetism,and ferrimagnetism at low tempertures were found in Sm1-x Cax CoAsO.Magnetic field resulted in metamagnetic transition was observed in Sm1-x Cax CoAsO below antiferromagnetic transi-tion temperature,and metamagnetic transition field decreased with increasing temperature.Ca doping limited ferrimagnetic transi-tion of SmCoAsO.The ferrimagnetic transition temperature of Sm0.8 Ca0.2 CoAsO sample was 23 K lower than that of SmCoAsO. The magnetic moment of Co influences the ferromagnetism and antiferromagnetism in SmCoAsO,and Sm decides ferrimagnetism by the interaction between Sm-O layer and Co-As layer along the c-axis.