The intergrain ordering in a superconductive ceramic of YBa 2 Cu 4 O 8 at zero external magnetic field is investigated by AC resistivity measurements. The third harmonic in-phase voltage component V ' 3ω to a weak AC current shows a distinct negative peak across the intergrain transition temperature T C2 , but not across the intragrain one T C1 ( T C2 < T C1 ). A divergence of the nonlinear resistivity ρ 2 is concluded at T C2 in the limit of vanishing AC current, while the linear resistivity ρ 0 remains finite even at and below T C2 . Such characteristic critical behaviors of the intergrain ordering of the present superconductive ceramic strongly suggest a chiral glass ordering recently predicted to occur in high- T C superconductive ceramics.
T. Yamao, M. Hagiwara, K. Koyama
Journal of the Physical Society of Japan