SEM images of the two sample surfaces (sample 1, sintered YBCO pellet, and sample 2, granular YBCO pellet). The two samples show different microstructures caused by the different preparation techniques.
Temperature-dependent ac loss of sample 1 (sintered YBCO pellet) at zero field. The applied rf is . The inset shows both the forward and reverse scans of the magnetic-field-dependent loss of sample 1 at in between and .
Temperature-dependent ac loss of sample 2 (granular YBCO pellet) at zero field. The applied rf is . The solid curve is the corresponding Ambegaokar-Baratoff fit with the temperature-dependent gap parameter given by the BCS theory. We interpret that the increase in ac losses with lowering of the temperature is due to the increase of the JJ critical current of the junctions. The inset shows the magnetic-field-dependent loss for both forward and reverse scans for the sample at in the field range from .
ac loss of sample 2 at zero field below . The results are for three different frequencies, 10, 15, and . The solid curves are the corresponding Ambegaokar-Baratoff fits. The inset shows the frequency dependence of the ac losses for the two samples at and . The solid curve is linear fit with different slopes.
Description of power absorption due to JJ decoupling. is the critical current of the Josephson junction. The rectangular box is the voltage-time area where the JJ exists. The arrow indicates the position at which JJ decoupling and formation occur. Energy equal to is absorbed by the Josephson junction at point a and the same amount of energy is released at point b. The energy released at point b dissipates to the sample in the form of heat energy. This occurs twice every cycle of the ac. One full cycle of ac has two decoupling and two creations of the Josephson junction. The axis shows the ac voltage applied to the sample. The figure presents the result for but is applicable for other frequencies.
Article metrics loading...
Full text loading...