Field dependence of the Eu2+ spin relaxation in EuFe(2-x)CoxAs2

TL;DR

This study investigates how Eu2+ spin relaxation in EuFe2-xCoxAs2 varies with magnetic field, revealing the influence of Fe2-xCoxAs2 layer fluctuations on local Eu2+ spin dynamics through ESR and susceptibility measurements.

Contribution

It provides new insights into the field dependence of Eu2+ spin relaxation and the weak coupling between local Eu2+ spins and itinerant electrons in EuFe2-xCoxAs2.

Findings

Spin relaxation is explained by exchange coupling among Eu2+ spins.

Field dependence shows magnetic fluctuations influence Eu2+ spin dynamics.

Weak coupling between local Eu2+ spins and itinerant electrons is confirmed.

Abstract

The layered compound EuFe2As2 is an interesting model system to investigate the effects of well defined local Eu2+ 4f states on the itinerant electronic and magnetic properties of the FeAs layers. To address this subject, we investigated the series EuFe2-xCoxAs2 (0.1 <= x <=0.75) by electron spin resonance (ESR) of Eu2+ to probe the spin dynamics of the itinerant subsystem. We relate the results to dc-susceptibility measurements and band structure calculations. As a consequence of the weak coupling between the local and itinerant subsystems we found that the spin relaxation is well understood in terms of the exchange coupling among the local Eu2+ spins. A pronounced field dependence of the Eu2+ spin relaxation demonstrates the direct influence of magnetic fluctuations at the Fe2-xCoxAs2 layers.