Pressure and grain-size dependences of the chiral-glass transition in superconductive ceramics of YBa2Cu3O7-y

Abstract

Ceramic high-T c superconductors may be viewed as a weakly coupled random Josephson network containing π-junctions, and a chiral-glass transition is predicted to be occurred. Grain-size and pressure dependences of the chiral-glass transition have been investigated on YBa 2 Cu 3 O 7-y ceramics. With decreasing temperature, a superconducting order occurs at first inside each grain at T c1 and furthermore among the grains at T c2 (< T c1 ). The increase in T c2 with increase of synthesis temperature is considered as the change of strength of inter-grain Josephson coupling accompanying the growth of grain size. The T c2 also increases with increase of pressure, however, the sharpness of the transition at T c2 does not change. In spite of difference in T c2 's, the increasing rates of t c2 by pressure are nearly the same.