Field dependence of the Eu 2+ spin relaxation in EuFe 2?xCo xAs 2

Abstract

The layered compound EuFe 2As 2 is an interesting model system to investigate the effects of well-defined local Eu 2+ 4f states on the itinerant electronic and magnetic properties of the FeAs layers. To address this subject, we investigated the series EuFe 2?xCo xAs 2 (0.1≤6 x≤6 0.75) by electron spin resonance (ESR) of Eu 2+ 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 Eu 2+ spins. A pronounced field dependence of the Eu 2+ spin relaxation demonstrates the direct influence of magnetic fluctuations at the Fe 2?xCo xAs 2 layers. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.