Theoretical investigation of the spin Hamiltonian parameters and local structure and their concentration dependences for Cd1−xMnxS quantum dots

Abstract

The spin Hamiltonian parameters (zero-field splitting D, g factors and hyperfine structure constants) and local structure as well as their concentration dependences for Cd1−xMnxS quantum dots are theoretically investigated from the perturbation formulae of these parameters for a 3d5 ion under trigonally distorted tetrahedra. The impurity Mn2+ is found not to occupy exactly the host Cd2+ site in the CdS quantum dots but to experience an inward displacement 0.041 Å towards the ligand triangle along the C3-axis because of the size mismatching substitution and the internal stress. As compared with bulk CdS:Mn2+, the larger impurity displacement and stronger Mn2+ 3d–3s orbital admixture in the Cd1−xMnxS quantum dots suitably account for the higher zero-field splitting and hyperfine structure constant, respectively. The impurity axial displacement and the Mn2+ 3d–3s orbital admixture in the Cd1−xMnxS quantum dots may exhibit an approximately cubic increase with increasing the Mn concentration x from 0.001 to 0.15.