The surface barrier on YBa2Cu3O7−δ grains has been studied in dynamic regime by performing measurements of the two components of the “Wide-Band” Susceptibility, χa and χr, as function of the applied AC field amplitude at different temperatures and frequencies. The best fit of the measured curves was obtained with the analytical expression of χa and χr calculated from a model in which the magnetic behaviour of the sample is supposed to be governed by the intergrain shielding current and by a surface barrier on the grains of the sample. From the fitting results, the height of the surface barrier on the grains has been valued independently for each measured curve, allowing us to determine the temperature dependence of the surface barrier using an AC technique at different frequencies. The result is a barrier which decreases with increasing temperatures, but its temperature dependence at low (up to about 10 kHz) frequencies of the applied AC field is different respect to the dependencies obtained at higher frequencies.
Temperature dependence of the surface barrier on YBa2Cu3O7−δ grains detected by AC susceptibility measurements
POLICHETTI, Massimiliano;
1997-01-01
Abstract
The surface barrier on YBa2Cu3O7−δ grains has been studied in dynamic regime by performing measurements of the two components of the “Wide-Band” Susceptibility, χa and χr, as function of the applied AC field amplitude at different temperatures and frequencies. The best fit of the measured curves was obtained with the analytical expression of χa and χr calculated from a model in which the magnetic behaviour of the sample is supposed to be governed by the intergrain shielding current and by a surface barrier on the grains of the sample. From the fitting results, the height of the surface barrier on the grains has been valued independently for each measured curve, allowing us to determine the temperature dependence of the surface barrier using an AC technique at different frequencies. The result is a barrier which decreases with increasing temperatures, but its temperature dependence at low (up to about 10 kHz) frequencies of the applied AC field is different respect to the dependencies obtained at higher frequencies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
