Electron Paramagnetic Resonance of Gd3+ Ions in the Pb1 – x – yGdxCuyS Narrow-Gap Semiconductor: Effects of Resonance Transitions on Conductivity

Crystals of the narrow-band semiconductor Pb1 – x – yGdxCuyS (x = 1.1 × 10–3, y = 2.5 × 10–3) at temperatures T = 5–300 K demonstrated unusual dependences of the shape of the lines of the electron paramagnetic resonance (EPR) spectra of paramagnetic centers of Gd3+ on temperature and microwave power in the resonator of EPR spectrometer. Analysis of the shape parameters of the resonance lines recorded in the X band showed that one of the causes of the unusual changes in the observed EPR spectra of Gd3+ centers is a nonuniform distribution of the acceptor impurity of copper with the formation of regions with different concentrations of free charge carriers. Apparently, in these regions, resonance transitions between the spin states of Gd3+ centers differently affect the kinetic characteristics of free charge carriers, which lead to different contributions to the quasi-resonant absorption of microwave power.