An effective spin–orbital Hamiltonian for Sr2FeWO6

Abstract We have developed a superexchange theory for the insulating double-perovskite compound Sr 2 FeWO 6 . The theory has been implemented in an effective spin–orbital Hamiltonian formulated in terms of spin ( S =2) and orbital pseudo-spin ( τ =1) degrees of freedom of the iron ion only, while W-sites have been integrated out by means of a fourth-order perturbative expansion. We have shown that for realistic values of the model parameters the ground state is antiferromagnetic, as experimentally observed.