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要旨:
The layered compound EuFe 2 As 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 2â x Co x As 2(0.1 ⩽ x ⩽ 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 2â x Co x As 2 layers.
