Ab initio investigation of magnetic ordering in the double perovskite Sr$_{2}$NiWO$_{6}$

TL;DR

This study uses ab initio calculations and Monte Carlo simulations to model magnetic interactions in Sr$_{2}$NiWO$_{6}$, revealing dominant next-nearest neighbor exchanges, small anisotropy, and bi-quadratic interactions that stabilize its antiferromagnetic order.

Contribution

It introduces a detailed spin Hamiltonian for Sr$_{2}$NiWO$_{6}$ based on ab initio data, highlighting the importance of next-nearest neighbor interactions and anisotropies.

Findings

Next-nearest neighbor exchange interactions are significantly stronger than nearest neighbor ones.

The Hamiltonian accurately reproduces finite temperature magnetic properties.

Small magnetic anisotropy and bi-quadratic interactions are crucial for ground state stabilization.

Abstract

{\it Ab initio} calculations, GGA/GGA+$U$, are used to propose a spin Hamiltonian for the B-site ordered double perovskite, Sr$_{2}$NiWO$_{6}$. Our results show that the exchange interaction constants between the next nearest neighbors in both intra- and inter- $ab$ plane ($J_2$ and $J_{2c}$) are an order of magnitude larger than the ones between the nearest neighbors ($J_1$ and $J_{1c}$). Employing the Monte Carlo simulation, we show that the obtained Hamiltonian properly describes the finite temperature properties of Sr$_{2}$NiWO$_{6}$. Our {\it ab initio} calculations also reveal a small magnetic anisotropy and non-trivial bi-quadratic interaction between the nearest inter-$ab$ plane neighbors, which play essential roles in stabilizing the type-II anti-ferromagnetic ground state of Sr$_{2}$NiWO$_{6}$.