铋系超导体超精细相互作用研究

HYPERFINE INTERACTION STUDY ON Bi-BASED SUPERCONDUCTOR

利用变温穆斯堡尔谱研究了铋系高Ｔ＿ｃ氧化物超导体在正常态上及正常态－超导态转变过程中晶格振动的性质。穆斯堡尔谱无反冲因子的测量结果表明，在超导转变温度以上的１２０Ｋ和２００Ｋ附近的两个温区上，分别出现了明显的铜－氧层晶格软化效应。这种晶格振动的异常行为，是超导转变的前驱效应。同质异能移位和无反冲因子得到德拜温Θ＿Ｄ为３１０－３５０Ｋ。测量同质异能移位、四极劈裂和谱线线宽也观察到超导转变前晶格的反常变化行为和ｄ电子的离域效应。

The dynamic studys of the lattice vibrational behaviors and hyperfine interacti-ons on the Bi-based high-T_c superconductors are conducted by means of Mossbauermeasurement.The recoilless fractors show that there is a significant lattice softeni-ng on Cu-O layers,above superconducting temperature,around 126 and 260K respe-ctively.Such anomalous behavior is thought to be a precursor effect of supercondu-ctivity. The recoilless fractors and the isomer shifts show that the Debye tempera-ture Θ_D=310-350K。 Based on the measurement of isomer shift,quatrupole spli-ting and spectroscopy width. it can be seen that both softening of lattice vibrationalmodes and delocalization effect on d-electron orbits exsist.