Type-II antiferromagnetic ordering in double perovskite oxide Sr_2NiWO_6

Magnetic double perovskite compounds provide a fertile playground to explore interesting electronic and magnetic properties. By complementary macroscopic characterizations, neutron powder diffraction measurements and first-principles calculations, we have performed comprehensive studies on the magnetic ordering in the double perovskite compound Sr_2NiWO_6. It is found by neutron diffraction to order magnetically in a collinear type-II antiferromagnetic structure in a tetragonal lattice with k = (0.5, 0, 0.5) below T_N = 56 K. In the ground state, the ordered moment of the spin-1 Ni^2+ ions is determined to be 1.9(2) μ_B, indicating a significant quenching of the orbital moment. The Ni^2+ moments in Sr_2NiWO_6 are revealed to cant off the c axis by 29.2^∘, which is well supported by the first-principles magnetic anisotropy energy calculations. Furthermore, the in-plane and out-of-plane next-nearest-neighbor superexchange couplings (J_2 and J_2c) are found to play a dominant role in the spin Hamiltonian of Sr_2NiWO_6, which accounts for the stabilization of the type-II AFM structure as its magnetic ground state.