Measurement and interpretation of AC susceptibility and loss in high-temperature superconductors

Intrinsic and hysteretic AC losses were investigated in high-temperature superconductors. A quantum design physical property measurement system magnetometer was used to measure AC susceptibility as a function of magnetic field, frequency, temperature and field history. Three types of loss mechanisms were observed and each associated with a different loss peak on the imaginary component of the AC susceptibility: the intrinsic, the intergranular and the intragranular peaks. The peaks were observed to change systematically with temperature and magnetic field, either in polycrystalline or single crystals. YBCO polycrystalline samples were prepared by three different techniques: solid-state synthesis, melt-process melt-growth and freeze-dried and studied both as bulk and powder samples. LSCO and BSCCO-2223 single crystals were studied and compared to polycrystalline samples.