Fe1.01Se0.4Te0.6单晶的超导电性研究

本文采用自助溶剂法生长得到Fe1.01Se0.4Te0.6单晶样品,超导零电阻温度Tczero=11.0 K,部分样品经400℃进行48小时退火之后,超导零电阻温度变为Tczero=7.0K.分析表明退火后样品的Fe含量变大,超导电性被部分抑制.通过磁场下电阻率-温度曲线的实验测量,用WHH(Werthamer-Helfand-Hohenberg)方法估算得到退火前后样品在0K附近的上临界场分别为83.2T和61.3T.上临界场μ0Hc2(T)随温度变化曲线在0T附近向高温方向上翘,说明样品具有"二流体"行为.直流磁化曲线在40K和120K分别出现向下弯曲,40K处的变化可能对应于过量Fe的自旋冻结.应变测量结果显示样品在117K时应变值发生一个突变,变化量约为晶格参数的0.06%,显示样品发生一个结构相变.因此,120K处的磁化下降对应于样品从四方相到正交相的结构转变.

SUPERCONDUCTIVITY IN Fe_(1.01)Se_(0.4)Te_(0.6) SINGLE CRYSTAL

Fe1.01Se0.4Te0.6 single crystal with zero resistant temperature Tzeroc=11.0K was grown by using self-flux method.After annealing at 400℃ for 48 h for part of the sample,superconductivity was suppressed with Tzeroc~7.0K,which may resulted from excess Fe in the annealed sample.The upper critical field at zero temperature was estimated to be 83.2 T before annealing and 61.3 T after annealing using WHH(Werthamer-Helfand-Hohenberg) theory.All μ0Hc2(T)values for both samples show upturns near 0T indicating a ’two component’ response.DC magnetism shows two decreases at 40K and 120K.The decrease at 40K may be related to the spin freezing of the excess Fe.Strain measurement for the sample shows a mutation at 117K,about 0.06% of the lattice parameter,indicating a structural transition.The decrease at 120K is corresponding to a structural transition from tetragonal to triclinic.