MAGNETIC-FIELD DEPENDENCE OF THE DIELECTRIC-CONSTANT IN CD1-XMNXTE - IN ON APPROACHING THE INSULATOR-TO-METAL TRANSITION

This study presents the frequency, temperature and magnetic field dependence of the capacitance in the dilute magnetic semiconductor Cd0.9Mn0.1Te:In near the insulator-to-metal transition. By exploiting the persistent photoconductivity effect or the large magnetic coupling between carriers and the localized (Mn2+) spins, it is possible to tune the transition in one sample either by optically changing the carrier concentration n or by applying a magnetic field H. The results indicate at least two contributions to the capacitance: a hopping term which is temperature and frequency dependent, and a term which varies only with n and H and is related to the polarizability of the bound charge carriers. This latter term is most evident at high frequencies and low temperatures and diverges as the transition is approached from the insulating side. The application of a magnetic field shifts the onset of the divergence to lower carrier concentrations, lending credence to earlier transport results which imply that the bound state delocalizes in the presence of magnetic order.