Orientation, temperature, and frequency dependence of nonresonant microwave absorption in HTSC powders

Hysteresis in the microwave-power absorption of HTSC powders was studied as a function of temperature (T), field-sweep amplitude (Hmax), and orientation between the dc field (Hdc) and the wave vector of the microwaves (k). It was found that (i) the sizable low-temperature hysteresis effects occur only if Hdc∥k, (ii) the temperature and frequency dependence of the hysteresis is strongly affected by Hmax, (iii) the high- and low-temperature virgin curves are quite different, and (iv) the minimum of the absorption signal increases with Hmax and T. The low-temperature hysteresis loops were found to be similar to loops obtained from nonlinear equations describing cusp catastrophes.