Frustrated Ising chains on the triangular lattice in Sr$_3$NiIrO$_6$

TL;DR

This study investigates the magnetic excitations in Sr$_3$NiIrO$_6$, revealing quasi-1D Ising-like chains with frustrated triangular lattice interactions, and demonstrates the persistence of magnetic excitations well above the ordering temperature.

Contribution

It provides a detailed inelastic neutron scattering analysis and a microscopic model explaining magnetic excitations and frustration in Sr$_3$NiIrO$_6$, supported by ab initio calculations.

Findings

Magnetic excitations are gapped and survive above the ordering temperature.

Strongly coupled Ising-like chains are identified along the c-axis.

The microscopic model explains the observed spin flip fields.

Abstract

Inelastic neutron scattering study on the spin-chain compound Sr$_3$NiIrO$_6$ reveals gapped quasi-1D magnetic excitations. The observed one-magnon band between 29.5 and 39 meV consists of magnon modes of the Ni$^{2+}$ ions. The fitting of the spin wave spectrum reveals strongly coupled Ising-like chains along the $c$-axis that are weakly coupled into a frustrated triangular lattice in the $ab$-plane. The magnetic excitations survive up to 200 K well above the magnetic ordering temperature of $T_N \sim 75$ K, also indicating a quasi-1D nature of the magnetic interactions in Sr$_3$NiIrO$_6$. Our microscopic model is in good agreement with ab initio electronic structure calculations and explains the giant spin flip field observed in bulk magnetization measurements.