Negative Divergence of Nonlinear Susceptibility at the Intergrain Phase Ordering Transitionin a Superconductive Ceramic of YBa₂Cu₄O₈

Abstract

The characteristic of intergrain phase ordering transition in a superconductive ceramic of YBa 2 Cu 4 O 8 is examined at zero external DC field by AC magnetic measurements. From the nonlinear response at the weak AC field limit, a negative divergence of nonlinear susceptibility χ 2 is concluded at the intergrain transition temperature T c2 but no remarkable anomaly is found at the intragrain one T c1 . This critical phenomenon may suggest the onset of chiral glass ordering at T c2 and necessarily a frustration in the intergrain Josephson type coupling network.