Rhenium oxyhalides: a showcase for anisotropic-triangular-lattice quantum antiferromagnets

TL;DR

This paper introduces rhenium oxyhalides as versatile experimental platforms for studying anisotropic triangular lattice quantum antiferromagnets, enabling exploration of diverse magnetic behaviors through chemical substitution.

Contribution

It reports the synthesis and characterization of seven new compounds with tunable anisotropic triangular lattice parameters, advancing experimental access to exotic quantum magnetic states.

Findings

Achieved chemical substitution in Re-based layered structures.

Measured anisotropy ratios J'/J from 0.25 to 0.45.

Demonstrated these materials' suitability for studying diverse spin Hamiltonians.

Abstract

The spin-1/2 Heisenberg antiferromagnet on an anisotropic triangular lattice (ATL) is an archetypal spin system hosting exotic quantum magnetism and dimensional crossover. However, the progress in experimental research on this field has been limited due to the scarcity of ideal model materials. Here, we show that rhenium oxyhalides $A_{3}$ReO$_{5}X_{2}$, where spin-1/2 Re$^{6+}$ ions form a layered structure of ATLs, allow for flexible chemical substitution in both cation $A^{2+}$ ($A$ = Ca, Sr, Ba, Pb) and anion $X^{-}$ ($X$ = Cl, Br) sites, leading to seven synthesizable compounds. By combining magnetic susceptibility and high-field magnetization measurements with theoretical calculations using the orthogonalized finite-temperature Lanczos method, we find that the anisotropy $J'/J$ ranges from 0.25 to 0.45 depending on the chemical composition. Our findings demonstrate that $A_{3}$ReO$_{5}X_{2}$ is an excellent platform for realizing diverse effective spin Hamiltonians that differ in the strength of the anisotropy $J'/J$ as well as the relevance of perturbation terms such as the Dzyaloshinskii-Moriya interaction and interlayer exchange coupling.