Abstract
Employing the time differential perturbed angular distribution (TDPAD) technique we have investigated the local magnetism of single Fe impurity in nanocrystalline Pb matrices, by measuring the local susceptibility and spin relaxation rate of 54Fe nuclei. Compared to the nonmagnetic behavior of Fe in bulk Pb host, characterized by independent local susceptibility χloc(T), the magnetic response of Fe in the nanocrystalline samples with particle size of 10 nm and below exhibit Curie-Weiss like χloc(T) with positive slope, indicating the presence of large orbital magnetic moment on the Fe impurity. The orbital moment of Fe has been estimated to be ∼ 1 µB for 6 nm nano-Pb. Further investigations are being carried out to understand the emergence of orbital magnetism of Fe in nano-Pb.
Highlights
An isolated transition metal atom in its ground state possesses both spin and orbital magnetic moments in accordance with the Hund’s rules
Transition metals like Fe, Co and Ni when embedded in large volume sp-metal hosts like alkali and earth alkali metals hosts have been found to exhibit large orbital moments.[1,2,3,4]
Further experimental studies are necessary to search for the occurrence of orbital magnetism for Fe impurity in different hosts
Summary
An isolated transition metal atom in its ground state possesses both spin and orbital magnetic moments in accordance with the Hund’s rules. Transition metals like Fe, Co and Ni when embedded in large volume sp-metal hosts like alkali and earth alkali metals hosts have been found to exhibit large orbital moments.[1,2,3,4] In contrast, Fe in dband metals exhibit spin dominated magnetism with negligible orbital contribution, consistent with itinerant picture. The recoiling 54Fe nuclei were implanted deep (∼1 μm) inside the hosts at concentrations well below 1 ppm.[6,9] Measurements were performed within a time window of 10 ns to 2 μs immediately after implantation These experimental conditions ensure negligible impurity-impurity interaction and the results reflect the magnetic response of a truly isolated impurity. From the background subtracted normalize counts recorded for the detectors, the spin rotation spectra R(t) were constructed using the ratio function
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