Nickel-Titanium double perovskite: A three-dimensional spin-1 Heisenberg antiferromagnet

TL;DR

This paper identifies La2NiTiO6 as a three-dimensional spin-1 Heisenberg antiferromagnet with a Mott insulating phase driven by strong coupling physics, providing insights into correlated topological states.

Contribution

It demonstrates through DFT and many-body calculations that La2NiTiO6 is a high-spin S=1 quantum magnet with a persistent Mott phase due to strong coupling, not frustration.

Findings

La2NiTiO6 is a high-spin S=1 quantum magnet.

The Mott phase persists down to 25K without frustration.

Magnetic ordering involves a kinetic energy gain.

Abstract

The double perovskite ${\rm La}_2{\rm NiTiO}_6$ is identified as a three-dimensional $S=1$ quantum magnet. By means of Density Functional Theory we demonstrate that this material is a high-spin $d$-electron system deep in the Heisenberg limit and establish that its paramagnetic Mott phase persists down to low temperatures ($T_{\rm N}$=25K) not because of frustration effects but rather for the extreme strong coupling physics. Our many-body calculations on an $ab$ $initio$-derived multi-orbital basis predict indeed a kinetic energy gain when entering the magnetically ordered phase. ${\rm La}_2{\rm NiTiO}_6$ emerges thus as a paradigmatic realization of a spin-triplet Mott insulator. Its peculiar properties may turn out to be instrumental in the ongoing chase after correlated topological states of matter.