Pb–0.5 at. % Fe and Yb–0.5 at. % Fe vapor-quenched films: Location and magnetization of the Fe impurities

Abstract

By combining vapor quenching technique at low temperature and in situ M\"ossbauer spectroscopy, we have studied the site occupation and magnetism of Fe in Pb and Yb films, as well as their stability with temperature. ${}^{57}\mathrm{Fe}$ M\"ossbauer spectra at 7 K, for as-prepared Pb--0.5 at. % Fe and Yb--0.5 at. % Fe films, have two paramagnetic components: a singlet, which is attributed to Fe at interstitial sites, and a doublet, assumed to be due to Fe atoms at ``substitutional'' sites, with at least one Fe near neighbor. M\"ossbauer measurements under an external magnetic field have been performed in as-prepared films and revealed that Fe atoms, associated with the doublet, have a magnetic moment in both systems, while those Fe atoms located at interstitial sites have magnetic moments only in the case of Yb films. These results confirm theoretical calculations predicting magnetic moments for interstitial Fe atoms in divalent hosts (Yb) and negligible probability of magnetic Fe atoms in tetravalent hosts (Pb).