Excitonic Zeeman effect in the zinc-blende II-VI diluted magnetic semiconductors Cd_1-xY_xTe (Y=Mn, Co, and Fe)

Abstract

The sp-d exchange constants (N₀α and N₀β ) of the zinc-blende diluted magnetic semiconductors Cd_1-xMn_xTe, Cd_1-xCo_xTe, and Cd_1-xFe_xTe are deduced from the huge excitonic Zeeman effect observed in wavelength-modulated reflectivity spectra, supplemented with magnetization measurements with a superconducting quantum interference device magnetometer. The Zeeman spectra recorded in magnetic fields (H) up to 60 kG, and temperatures (T) down to 1.8 K clearly reveal the Van Vleck paramagnetism of Cd_1-xFe_xTe; in contrast, Cd_1-xMn_xTe and Cd_1-xCo_xTe display a Brillouin-function-like (H/T) dependence of their excitonic Zeeman components associated with spin 5/2 and 3/2 ground states of Mn²⁺ and Co²⁺, respectively. The antiferromagnetic d-d interaction between the magnetic ions, displayed in the Zeeman data, is mainly limited to nearest-neighbor Mn²⁺ ions, whereas it is significantly stronger for Co²⁺ than for Mn²⁺ and extends to more distant neighbors.