Magnetic properties of isolated Re ion and Re-Re complex in ZnO studied by GGA +U approach

Abstract

Magnetic properties of Re substituting for the divalent Zn ions and impurity pairs in wurtzite and zinc blende ZnO are analyzed by employing the Generalized Gradient Approximation with the +U corrections. The +U term applied to d(Zn), p(O), and d(Re) orbitals stabilizes spin polarization of Re. Re impurity introduces a defect level located in the band gap, and Re2+ generates the local spin 5/2 in both wurtzite and zinc blende structures. Magnetic coupling of Re-Re pairs as a function of distance between the defects, their relative orientation, and the charge state was calculated. All magnetic coupling between impurities is antiferromagnetic and due to an intermediate O atom via strong d(Re)-p(O) hybridization between Re and O states. The defect states and magnetic moments come from d(Re) with a contribution of p(O) orbitals of the O nearest neighbors of Re. The results show that the Re-doped wurtzite ZnO may be a new type of magneto-optical materials with a great promise.