Dzyaloshinsky-Moriya interaction and the ground state in S=3/2 perfect kagome lattice antiferromagnet $\mathbf{KCr_3(OH)_6(SO_4)_2}$ (Cr-jarosite) studied by X-band and high-frequency ESR

TL;DR

This study uses ESR techniques to analyze the magnetic interactions and ground state of the S=3/2 kagome antiferromagnet Cr-jarosite, revealing Dzyaloshinsky-Moriya interactions and confirming its two-dimensional magnetic behavior.

Contribution

First ESR study to determine Dzyaloshinsky-Moriya interactions and ground state properties of Cr-jarosite, linking experimental results with theoretical models.

Findings

Determined g-values for in-plane and out-of-plane directions.

Observed antiferromagnetic resonance with a 120 GHz gap below T_N.

Estimated Dzyaloshinsky-Moriya interaction components and confirmed 2D antiferromagnetic behavior.

Abstract

A single crystal S=3/2 perfect kagome lattice antiferromagnet $\mathrm{KCr_3(OH)_6(SO_4)_2}$ (Cr-jarosite) has been studied by X-band and high-frequency electron spin resonance (ESR). The g-values perpendicular to the kagome plane (c-axis) and in the plane are determined to be $g_c=1.9704 \pm 0.0002$ and $g_\xi=1.9720 \pm 0.0003$, respectively, by high-frequency ESR observed at 265 K. Antiferromagnetic resonances (AFMR) with the antiferromagnetic gap of 120 GHz are observed at 1.9 K, which is below $T_N$=4.5 K. The analysis of AFMR modes by the conventional molecular field theory shows $d_p=0.27$ K and $d_z=0.07$ K, where $d_p$ and $d_z$ are in-plane and out-of-plane components of DM d vector, respectively. From these results and the estimated exchange interaction J=6.15 K by Okuta et al., the ground state of Cr-jarosite is discussed in connection with the Monte Carlo simulations result with classical Heisenberg spins on the kagome lattice by Elhajal et al. Finally, the angular dependence of linewidth and the lineshape observed at 296 K by X-band ESR show typical behavior of a two-dimensional Heisenberg antiferromagnet, suggesting a good two-dimensionality of Cr-jarosite.