Anomalous Variation of the Recoil-Free Fraction of 151Eu Nucleus in Euba2Cu3O7−x around the Superconducting Transition Temperature

Mossbauer spectra of the superconductor EuBn 2 Cu 3 O 7-x are measured at various temperatures (83 to 120 K) and the effective absorber thickness is calculated from the experimental spectra. The temperature variation of the recoil-free fraction of the 151 Eu nucleus in EuBa 2 Cu 3 O 7-x is obtained. An anomaly in the temperature dependence of the recoil-free fraction of the 151 Eu nucleus in the superconductor EuBa 2 Cu 3 O 7-x is found around the superconductinp transition temperature. This may provide evidence of softening of lattice vibrations about the Eu atom in the crystal in the normal state-superconducting state transition process of the Eu-Ba-Cu-O system