Superconductivity and paramagnetism in ErBa2Cu3O7−y

We report detailed magnetic susceptibility and magnetization studies for the high Tc oxide superconductor ErBa2Cu3O7−y. The magnetic susceptibility χ of ErBa2Cu3O7−y follows a Curie–Weiss law both above and below Tc with the magnetic moment Peff=9.2μB, which is close to that of 9.58μB deduced from the ground state of Er3+ ion. Magnetization data at various temperatures have revealed a very large magnetic hysteresis. By analyzing the hysteretic magnetization data, we obtain the critical current density Jc(H) and the reversible magnetization Me(H) at 4.2 K. The saturation of Me in high fields at low temperature can be explained by the standard theory of paramagnetism with a Brillouin function. We find that superconductivity and paramagnetism in ErBa2Cu3O7−y exist largely independently of one another.