The exchange coupling of dilute and in Cr alloys: Formation of local magnetic clustersO. Beutler1, 2, R. Kirsch1, 2, M. J. Prandolini1, 2, W. D. Brewer1, J. Kapoor2, P. J. Jensen1, S. Frota-Pessôa3 and D. Riegel2
1 Fachbereich Physik, Freie Universität Berlin - 14195 Berlin, Germany
2 Hahn-Meitner-Institut Berlin GmbH - 14109 Berlin, Germany
3 Instituto de Física da USP - CP 66318, 05315-970 São Paulo, S.P., Brazil
received 3 January 2005; accepted in final form 29 March 2005
published online 27 April 2005
We have used the atomic specificity and sensitivity of the in-beam perturbed -ray angular distribution method to investigate the magnetic behaviour of very dilute implanted into 1-xx spin-glass alloys. Distinct magnetic responses due to the different configurations of and nearest neighbours were observed. A single nearest neighbour results in a notable decrease of the magnitude and reversal of the sign of the Curie constant of the paramagnetic implanted . We interpret this as the result of strong antiferromagnetic coupling between adjacent and local moments, leading to the formation of a local magnetic cluster, which remains stable up to the highest temperatures of the measurements (400). 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.
75.20.Hr - Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions.
71.15.Mb - Density functional theory, local density approximation, gradient and other corrections.
76.80.+y - Mössbauer effect; other -ray spectroscopy.
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