Electron spin resonance in the vicinity of metal-insulator transition in compensated n-Ge : As

Electron spin resonance (ESR) is investigated in the vicinity of metal-insu lator transition in compensated n-Ge:As. It is found that the 10-GHz signal is observed from both sides of the transition up to a temperature of 100 K . ESR spectrum in metallic samples looks like a single line of the Dyson ty pe, with the line shape varying with temperature. The Dyson line in the ins ulating samples transforms into the Lorentz line which splits into two line s at temperatures below 4.1 K. One line has an ordinary shape, the other ha s an anomalous step-like shape in the magnetic field, increasing with decre asing temperature. This effect has not been satisfactorily explained so far . Two mechanisms are proposed for the spin relaxation observed, one of whic h is related to donor-acceptor pairs and the other, to phonons. The Pauli a nd Curie paramagnetism is found in metallic and insulator samples, respecti vely. (C) 2000 MAIK "Nauka/Interperiodica".