Diamagnetic transition in disordered CuCl

Abstract

Recent work has discussed high-$T_c$ superconductivity in terms of various excitonic high-density states and how the band structure of CuCl makes it a good candidate material. We have measured the magnetic state of disordered CuCl in the temperature range from 77 to 280 K using an ac mutual inductance technique at 17 Hz, and we have observed anomalous increases in diamagnetism at temperatures between 120 and 230 K. We believe that our observations provide totally independent corroborative evidence of the diamagnetic phase transition reported by Brandt et al. and Chu et al. Analyses of the data (on cooling and heating) in light of observations in inhomogeneously heated (radioactive) superconductors lends credence to the conclusion that the observed anomalies are a special form of superconductivity.