Non‐Resonant Microwave Absorption in N = 3 Phase of BiPbSrCaCuO High‐Temperature Superconductor

Abstract

AbstractA detailed study is made of the temperature and magnetic field dependent properties of the non‐resonant microwave absorption in granular composites of the N = 3 phase (Tc = 110 K) of the high‐temperature supercondutor Bi2−xPbxSr2CaN−1CuNO4 + 2N using an EPR spectrometer. The magnetic field value of the center of the line and the width of the line depend on the magnitude of the previously applied dc magnetic field and the direction of sweep of the field. The position and width also change with temperature. It is shown that the theory of Xia and Stroud for the electromagnetic response of superconducting current loop in an increasing magnetic field, assuming a Boltzmann distribution of loop areas in the granular composite, can account for the shape of the derivate and the temperature dependence of the intensity of the derivative of the absorption. The change of the magnetic field position and linewidth with temperature and field can not be accounted for by the theory. These effects are argued to be a result of the flux trapping behavior of the sample.