Critical role of Fock exchange in characterizing dopant geometry and magnetic interaction in magnetic semiconductors

We demonstrate the significance of the Fock exchange in accurately describing dopant geometry on the superexchange interaction between the magnetic ions in doped semiconductors. The result emphasizes the important role of the Coulombic and electronic contributions to the Hellmann-Feynman forces, which have been overlooked in methods using generalized gradient approximation and local density approximation functionals. Using hydrogen-doped ZnO:Co as an example, we show that the hybrid functional can result in a new geometry of hydrogenic complex, which mediates ferromagnetic interaction through a combination of double exchange and Jahn-Teller effect.