Glassy vortex behavior in superconducting SrPd2Ge2 single crystals

Abstract

In this study we report the vortex-glass behavior of superconducting ternary germanide SrPd2Ge2 single crystals with a ThCr2Si2-type structure. We observed flux trapping and its nonexponential decay with time after the magnetic field was turned off at T = 2 K. In addition, we found that the diamagnetism in the zero field cooling (ZFC) mode below T-c was irreversible, depending on the temperature and field history, whereas the diamagnetism in the field-cooled warming (FCW) mode was reversible if the applied magnetic field was parallel to the c-axis. An irreversibility line T-r(H) was determined by the ZFC and FCW measurements at various magnetic fields, and the temperature dependence of T-r(H) was found to agree with the de Almeida-Thouless relation, H = H-0[1 - T-r(H)/T-c(0)](gamma), where gamma = 3/2. Including these vortex-glass behaviors, we discuss the critical current density, J(c)(T), determined from isothermal magnetization measurements at various temperatures, and the pinning potential, determined from the slope of an Arrhenius plot, ln R(T, B) versus 1/T.