铋系超导体的^(57)Fe穆斯堡尔谱效应

^( 57)Fe Mossbauer Effect on Bi-Based Superconductors

对铋系超导体的正常态和超导态之间的转换进行了与温度相关的穆斯堡尔谱、X—射线衍射、磁化系数 ac和电阻率的测量 .铋系超导体的穆斯堡尔谱测量显示出两个通常的四极劈裂峰值 ,表明材料的组成成分是 2 2 2 3相 .57Fe占位的讨论采用点电荷模型 .与温度相关的 57Fe穆斯堡尔谱和 X—射线衍射研究晶格振动的动力学信息都是从 77K到室温的范围 .实验结果表明在 12 0 K和 2 0 0 K附近时 ,Cu- O层中出现了晶格软化 .在 Tc 以上温度出现晶格软化是超导转变的先驱效应 .

Normal state and normal-superconducting transition of Bi-system superconductors were studied by T-dependent Mossbauer spectroscopy, X-ray diffraction, magnatic ac susceotibility and resistance measurements. Mossbauer measurements usually show two quadrupole components arisen from the 2223 phase in the Bi-based superconductor. The site assignment of 57 Fe is discussed in terms of point-charge-model. Dynamical information for lattice vibration obtained from temperature dependent 57 Fe Mossbauer spectroscopy and X-ray diffraction studies within temperature region 77K to room temperature. The experimental results reveal evidence of lattice softening locaized in Cu-O layers at about 120K and 200K. The lattice softening above Tc are can be regarded as a precursor effect of superconductivity.