Spin dynamics in triangular lattice antiferromagnets CuCr$_{1-x}$Mg$_x$O$_2$

TL;DR

This study uses ESR spectroscopy to explore spin dynamics and antiferromagnetic fluctuations in CuCrO2 and Mg-doped variants, revealing doping-dependent suppression of AFM spin fluctuations above the Néel temperature.

Contribution

It provides new insights into how Mg doping influences antiferromagnetic spin fluctuations in triangular lattice CuCrO2, a previously less understood aspect.

Findings

Strong AFM spin fluctuations observed above T_N in undoped CuCrO2.

Mg doping suppresses AFM spin fluctuations above T_N.

Different temperature evolution of ESR intensity in doped and undoped samples.

Abstract

The electron spin resonance (ESR) spectroscopy was employed to investigate the spin dynamics in triangular lattice antiferromagnets CuCr$_{1-x}$Mg$_{x}$O$_2$ with $x =$ 0 and 0.02. All spectra can be well fitted by a single Lorentzian lineshape. The analysis of the $g$ factor, the linewidth $\bigtriangleup H$, and the ESR intensity $I$ as a function of temperature suggests the development of significant antiferromagnetic (AFM) spin fluctuations at temperature well above $T_N$ in both samples. However, the evolution of the AFM spin fluctuations is different for each sample. For undoped sample the ESR intensity $I$ is almost temperature independent between $\sim$ 100 K and 50 K and then drops rapidly below 50 K. But for $x =$ 0.02, the $I$ monotonously increases with cooling and reduces rapidly only below $T_N$. These results indicate that the AFM spin fluctuations are extremely strong in the undoped sample and appear to be suppressed upon Mg doping.