Ab initio modelling of magnetic anisotropy in Sr3NiPtO6

Abstract

First principles calculations in the framework of Density Functional Theory (DFT) and wavefunction-based correlated methods have been performed to investigate in detail the magnetic anisotropy in Sr₃NiPtO₆. This material is known for the easy-plane anisotropy with a large anisotropy constant of about 7.5–9.3 meV. We find that by properly choosing the onsite Coulomb repulsion and exchange parameters, DFT can correctly explain the easy-plane magnetocrystalline anisotropy of the material, but the magnitude of the anisotropy constant is underestimated. On the other hand, a quantitative agreement with respect to experiments, both in the magnitude and direction of the magnetic anisotropy, can be recovered by using the wavefunction-based approach which is able to fully describe the multiplet physics. We also show that the presence of structural distortions of the local NiO₆ coordination is crucial for stabilizing the magnetic anisotropy in this compound.