Magnetism and critical fields in the high-Tc superconductors YBa2Cu3O7−xSx(x=0, 1): An ESR study

Abstract

We have used an ESR spectrometer to study magnetism and superconductivity in $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-x}{\mathrm{S}}_x (x=0, 1)$. All samples exhibited an ESR signal. All the superconducting samples showed a low-field signal due to transition from the Meissner state to the mixed state. We demonstrated a reverse relation between magnetism (ESR intensity) and superconductivity. The temperature dependence of the critical field $H_{c1\mathrm{}}$ is anomalous.