Measurement of the Derivatives of the Magnetization of a Superconducting Network

Measurements are reported of the derivatives d M /d H and d M /d T of the magnetization of a superconducting network near the superconducting transition temperature in a weak transverse magnetic field. The a.c. susceptibility d M /d H exhibits sharp peaks at integer and fractional number of flux quanta per cell as expected from the phase diagram ( H, T ) of the network. In contrast, the d M /d T measurements reveal distinct features, characteristic of the equilibrium state below the superconducting transition. These results are compared to recent theoretical predictions for the mixed state of a superconducting network.