Abstract
Recent low-temperature studies on La5/8-yPryCa3/8MnO3 (y=3/8) have shown that the occurrence of the first-order transition in these family of perovskites manifests itself in the form of magnetic and electric avalanches. In this paper we report on the detection of such avalanches performing microwave experiments with coaxial resonators (low frequency ∼3 GHz) and cavities (high frequency ∼50 GHz) at different temperatures and magnetic fields. Short measuring times enabled us to detect the rapid variation in the energy absorption and/or cavity perturbation of the microwaves due to the occurrence of these phase transitions.