First principles based investigation of magnetic dilution effect on spin ordering in spinel Ni1−xZnxFe2O4 crystal

Incorporation of diamagnetic Zn at the tetrahedral sublattice in spinel Ni 1-x Zn x Fe 2 O 4 has been established to increase occupancy of magnetic Fe at the octahedral sublattice while diluting magnetic superexchange interaction between the two sublattices. Herein, a first principles based computational study was performed to predict the ground-state spin configuration and saturation magnetization as a function of Zn content for quantitative elaboration of magnetic dilution effect in Ni 1-x Zn x Fe 2 O 4 . Specifically, twenty-three superexchange constants were derived from a dataset containing the energies and magnetic moments predicted from density functional theory and used in a greedy-search algorithm to identify the ground-state spin ordering of spinel crystal at an atomic scale. The predicted saturation magnetization of Ni 1-x Zn x Fe 2 O 4 exhibited an increase with increasing Zn content up to 0.594, at which a maximum value of 6.18 μ B /f.u is achieved, and then a decrease with further increased Zn content. More importantly, computational results reveal in Ni 1-x Zn x Fe 2 O 4 that the antiferromagnetic interaction within the octahedral sublattice could be stronger than that across the two sublattices if Zn content is higher than 0.65, resulting in a collapse in ferrimagnetic spin ordering, with possibility of misalignment depending strongly on the number of Zn neighbors surrounding those magnetic cations at the octahedral sublattice.