Anomalous Manifestation of Pauli Paramagnetism and Coulomb Blockade of Spin Exchange upon the Compensation of Doped Semiconductors

Abstract

The effects of the influence that is exerted by compensating acceptor impurities on the spin exchange and on the transformation of Pauli paramagnetism into Curie paramagnetism in a metal–insulator phase transition in a doped semiconductor are studied for Ge:As. The behaviors of paramagnetic susceptibility and spin density in the temperature range of 2–80 K are investigated via the electron spin resonance method. At zero compensation, this transformation is accompanied by the manifestation of the effect of antiferromagnetic coupling from localized spins at low temperatures. An increase in the acceptor concentration results in Pauli paramagnetism being observed deep in the insulator state at sufficiently high temperatures of T ≥ 4–8 K. However, it is transformed at lower temperatures of T ≤ 3–5 K into Curie paramagnetism without indications of an antiferromagnetic coupling. In the suggested model, negatively charged acceptors destroy the exchange‐coupled pairs of spins and block the involvement of electron states of the closest positively charged donors in the spin exchange. A narrow Coulomb gap appears at the Fermi level in the metallized impurity band of a compensated semiconductor. This gap is manifested at low temperatures and hinders the observation of Pauli paramagnetism.