Using the high specificity and sensitivity of the in-beam perturbed γ-ray angular distribution method, we have investigated the magnetic behavior of very dilute 54 Fe probes in Ag1−xAux alloys. The nuclear damping time and local susceptibility of Fe are found to depend strongly on its local environment, showing inhomogeneous line broadening as well as discrete magnetic responses due to the different configurations of Ag/Au nearest neighbors. The results can be understood with the aid of ab initio calculations of electronic structure, magnetic moments and hyperfine fields. They underline the central importance of orbital magnetism for understanding the experimental results.

We have used the atomic specificity and sensitivity of the in-beam perturbed γ-ray angular distribution method to investigate the magnetic behaviour of very dilute 54 Fe implanted into Au1−xCrx spin-glass alloys. Distinct magnetic responses due to the different configurations of Au and Cr nearest neighbours were observed. A single Cr nearest neighbour results in a notable decrease of the magnitude and reversal of the sign of the Curie constant of the paramagnetic implanted Fe. We interpret this as the result of strong antiferromagnetic coupling between adjacent Fe and Cr local moments, leading to the formation of a local magnetic cluster, which remains stable up to the highest temperatures of the measurements (400 K). A heuristic model using as input data the results of ab initio calculations of coupling constants, magnetic moments and hyperfine fields strongly supports this interpretation.

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