Parameters of the magnetic polaron state in diluted magnetic semiconductors Cd-Mn-Te with low manganese concentration.

Abstract

A method for the determination of magnetic polaron parameters is suggested for diluted magnetic semiconductors with low manganese concentration x, when the magnetic polaron shift of the exciton energy cannot be observed in practice. We show that the average exchange field, created by the localized exciton, and the magnetic polaron energy can be determined from the experimentally measured magnetic-field dependences of the circular polarization of the luminescence and Zeeman splitting of the free exciton. Theoretical dependences of the circular polarization on the magnetic field have been calculated in the two-dimensional case for different temperatures. Results of the calculations are in good agreement with our experimental data for CdTe/Cd12xMnxTe quantum wells with x50.117 and 0.13. @S0163-1829~96!06731-8# In semimagnetic semiconductors the strong exchange interaction between the charge carriers and electrons in the deep magnetic shell of magnetic ions manifests itself in the giant Zeeman splitting of the valence- and conduction-band states, the large Faraday rotation, and the formation of magnetic polarons ~MP’s !. 1,2 The magnetic polaron represents a small region in the crystal with strongly correlated spins of magnetic ions and carriers localized in this region. This spin ordering results in a decrease of the carrier energy, which is usually detected in optical experiments as a Stokes shift between the maximum of the photoluminescence line and the maximum of the photoluminescence excitation spectrum. 3‐5 Magnetic polaron states of localized excitons have been studied in the semimagnetic semiconductors Cd12xMnxTe with considerable magnetic-ion concentrations ~x>0.2!. 6,7 Three-dimensional polaron dynamics have been studied