ANOMALOUS BEHAVIORS IN HIGH-TEMPERATURE SUPERCONDUCTORS - LATTICE EFFECT AND D-ELECTRON DELOCALIZATION EFFECT OF THE NORMAL-STATE ON THE BI, TL, AND Y-SYSTEM SUPERCONDUCTORS

The dynamic studies of the hyperfine interactions and the lattice vibr ational behavior are performed by means of temperature-dependent Mossb auer spectroscopy on the Bi-, Tl-, and Y-based superconductors, respec tively. The temperature-dependent Mossbauer recoil-free factor f show that, above, but relatively close to, the transition temperature, ther e is an anomalous lattice effect which is related to the softening of phonon vibrational modes for Bi-2223, Tl-1223, and Y-123 superconducto rs. Moreover, for such three systems, the anomalous decrease of the Mo ssbauer isomer shift above Tc reveal the delocalization effect of d-el ectrons. Since the lattice effect is accompanied by d-electron delocal ization effect at the almost same temperature region, it is believed t hat the structural instability involved in phonon softening is strongl y interrelated to the change of the electronic states, and the phase s eparation behavior.