Coupling of localized moments and itinerant electrons in EuFe2As2 single crystals studied by Electron Spin Resonance

TL;DR

This study uses Electron Spin Resonance to investigate the magnetic interactions in EuFe2As2 single crystals, revealing how electron coupling and spin relaxation change across the spin-density wave transition, indicating electron confinement.

Contribution

It provides new insights into the coupling between localized moments and itinerant electrons in EuFe2As2 through ESR measurements across the SDW transition.

Findings

Above T_SDW, isotropic spectra with Korringa-like linewidth increase.

Below T_SDW, anisotropic spectra with dominant dipolar and crystal-field interactions.

Conduction electrons are spatially confined to FeAs layers in the SDW state.

Abstract

Electron spin resonance measurements in EuFe2As2 single crystals revealed an absorption spectrum of a single resonance with Dysonian lineshape. Above the spin-density wave transition at T_SDW = 190 K the spectra are isotropic and the spin relaxation is strongly coupled to the CEs resulting in a Korringa-like increase of the linewidth. Below T_SDW, a distinct anisotropy develops and the relaxation behavior of the Eu spins changes drastically into one with characteristic properties of a magnetic insulating system, where dipolar and crystal-field interactions dominate. This indicates a spatial confinement of the conduction electrons to the FeAs layers in the SDW state.