Spin dynamics of $Yb Rh_2 Si_2$ observed by Electron Spin Resonance

TL;DR

This paper reports the observation of electron spin resonance (ESR) in the heavy fermion metal YbRh₂Si₂ below the Kondo temperature, revealing anisotropic spin dynamics characteristic of the Kondo-ion Yb³⁺.

Contribution

It demonstrates ESR detection of Yb³⁺ ions below T_K in YbRh₂Si₂, showing anisotropic spin relaxation properties not previously observed in similar systems.

Findings

ESR spectra show Yb³⁺ characteristics below T_K

Spin relaxation is spatially anisotropic at zero temperature

YbRh₂Si₂ exhibits unique ESR behavior among Kondo systems

Abstract

Below the Kondo temperature $T_{\rm K}$ electron spin resonance (ESR) usually is not observable from the Kondo-ion itself because the characteristic spin fluctuation energy results in a huge width of the ESR line. The heavy fermion metal YbRh$_{2}$Si$_{2}$ seems to be an exceptional case where definite ESR spectra show characteristic properties of the Kondo-ion Yb$^{3+}$ well \textit{below} $T_{\rm K}$. We found that the spin dynamics of YbRh$_{2}$Si$_{2}$, as determined by its ESR relaxation, is spatially characterized by an anisotropy of the zero temperature residual relaxation only.