Broadening Mechanism of Resistive Transition under Magnetic Field in Single Crystalline (La_1-xSr_x)₂CuO₄

Abstract

The resistive transitions near the superconducting critical temperature were measured under magnetic field up to 5 T on a FZ-grown high-quality single crystal (La 0.93 Sr 0.07 ) 2 CuO 4 ( T c =37.5 K) The crystal was sufficiently large along the c -axis that the dc four-probe method could be applied along this axis as well as along the usual a-b plane. It was found that the width of the temperature region over which the resistive transition is broadened depends only on the relative orientation between the magnetic field and the crystalline c -axis, but not on that between the field and the current. It indicates that the mechanisms based on the fluxoid motion, such as the flux creep model, the Kosterlitz-Thouless transition model and the superconducting glassy state model, are unlikely to explain the broadening of the resistive transition under magnetic fields in (La 1- x Sr x ) 2 CuO 4 .