Magnetic susceptibility and compositional dependence of the energy gap in Cd_1-xCo_xTe

Abstract

Single crystals of the diluted magnetic semiconductor Cd_1-xCo_xTe grown by the vertical Bridgman technique are characterized by wavelength-modulated reflectivity and magnetization measurements. Low− temperature magnetization and high-temperature magnetic susceptibility analysis were used to extract the exchange integrals for up to third-neighbour Co²⁺pairs in the CdTe host: J₁/k_B = -25pm7 K, J₂/k_B= -3.0pm1.5 K, and J₃/kB = -1.3pm0.3 K. These values correspond well to the values obtained for other Co-based II-VI diluted magnetic semiconductors and are a clear manifestation of the unusually large Co²⁺-Co²⁺ antiferromagnetic interaction. The excitonic energy gap Eg(x) of Cd_1-xCo_xTe in the wavelength-modulated reflectivity shows a linear monotonic increase with increasing x in the composition range studied.