Study of Electron Spin Resonance on single crystals $EuFe_{2-x}Co_{x}As_2$

TL;DR

This study investigates the temperature-dependent electron spin resonance (ESR) in EuFe_{2-x}Co_{x}As_2 single crystals, revealing interactions between conduction electrons and Eu^{2+} ions, and identifying anomalies at the spin-density-wave transition.

Contribution

It provides new insights into ESR behavior and Fermi surface nesting effects in EuFe_{2-x}Co_{x}As_2, highlighting the relationship between linewidth, SDW transition, and Fermi surface properties.

Findings

ESR g factor and linewidth depend strongly on temperature.

Linewidth exhibits Korringa behavior, indicating exchange coupling.

Anomalies at the SDW transition suggest gap opening and Fermi surface nesting.

Abstract

The temperature dependence of electron spin resonance (ESR) was studied in $EuFe_{2-x}Co_{x}As_2 $ (x = 0.0, 0.067, 0.1, 0.2, 0.25, 0.285, 0.35, 0.4 and 0.5). The ESR spectrum of all the samples indicates that the g factor and peak-to-peak linewidth strongly depend on the temperature. Moreover, the peak-to-peak linewidth shows the Korringa behavior, indicating an exchange coupling between the conduction electrons and the $Eu^{2+}$ions. The linewidth, g factor and the integrate ESR intensity show anomalies at the temperature of the spin-density-wave (SDW). The linewidth below the SDW transition does not rely on the temperature. This gives the evidence of the gap opening at the $T_{SDW}$. The slope of the linewidth is closely associated to $T_{SDW}$and $T_C$. This exotic behavior may be related to the nesting of the Fermi surface.