SmFeAsO材料的正电子寿命研究

Positron annihilation lifetime study of SmFeAsO superconductor

首次用正电子湮灭寿命谱仪(PALS)测量SmFeAsO多晶样品常温下的寿命谱,得到两个寿命成分151.6ps和290.3ps,根据捕获模型得到正电子在SmFeAsO中湮灭的体寿命为187.0ps,与理论计算(广义梯度近似)得到的SmFeAsO单晶中的正电子体寿命173ps符合较好.基于中性原子叠加模型-有限差分方法(SNA-FD)的理论计算得到正电子与单晶SmFeAsO中各个原子价电子的总湮灭率是其与各个原子核心内层电子总湮灭率的10.6倍,正电子与Fe,As,Sm,O原子的电子湮灭的概率之比是1∶1.3∶1.2∶1.

Positron annihilation lifetime spectroscopy（PALS） measurements of SmFeAsO polycrystalline sample were first carried out at 298 K.Two lifetime components of 151.6 ps and 290.3 ps were obtained.According to two-state capture model,the free annihilation lifetime in polycrystalline SmFeAsO is 187.0 ps,which agrees well with the calculated value（in general gradient approximation） of 173 ps in SmFeAsO single crystal.Superposed-neutral-atom model and the finite-difference method（SNA-FD） were used to calculate the positron annihilation information in single-crystal SmFeAsO.The results show that the ratio of annihilation rate with valence electrons to annihilation rate with core electrons is 10.6,while the ratio of annihilation rate with electrons from Fe,As,Sm,and O atoms are 1：1.3：1.2：1.