LOCAL MOMENT FORMATION AT INTERSTITIAL IMPURITY SITES IN METALS

We have calculated the electronic structure and related properties aro und an interstitial impurity in several metallic hosts. This was done using the real-space linear muffin tin orbital scheme (RS-LMTO-ASA), a first-principles, self-consistent approach implemented directly in re al space. We show that interstitial Fe does not develop a local moment in trivalent and tetravalent Sc, Y, Ti and Zr hosts. In divalent Ba, Ca, Sr and Yb we find that the appearance of local moment is extremely dependent on nearest neighbor relaxation, while in alkali metals such as K, we expect the interstitial Fe impurity to be magnetic. We show that these trends can be qualitatively understood using simple ideas b ased on the Wolff model and the Stoner criterium. We also consider Fe impurities in Gd, a trivalent magnetic host. We find an unusually larg e induced local moment at the interstitial Fe site and discuss the ori gin of this effect. Finally, we compare our results with TDPAD and in beam Mossbauer experiments in these systems.