Search

We present an improved ac method to measure the thermal diffusivity in an extended range of temperatures (15–330 K) and magnetic fields (0–8 T). We solder wires of a selected material directly on the sample: so, the thermal sensor is the junction between the sample and the wire. We have verified that this fast thermocouple works at frequencies high enough to neglect thermal losses also at the highest temperatures. Moreover, the soldered wires allow a concurrent four-wire resistivity measurement on the sample itself.

Magnetization measurements were performed with a SQUID magnetometer on apressed Ag-sheathed BSCCO (2223) tape. The hysteresis loops, analyzed in the framework of the “Critical State model” show clear anomalies. The results are explained invoking granularity of the sample, as confirmed by the analysis of the reverse leg of the magnetization. The irreversibility line, measured in the orientations B//c and B⊥c, is also presented.