Substitutional site preference in a quasicrystal.

Iron has been successfully incorporated in the quasicrystal i-Al sub (74) Si sub 6 Mn sub (20-x) Fe sub x up to a concentration x = 7. A combination of magnetic susceptibility and Mossbauer study establishes the fact that there are at least two 'classes' of Mn sites and the FE substitutes for only one of them. High field Mossbauer measurements at 4.2K show that the substituted iron carries no local moment, while low temperature susceptibility data indicate that its presence does not perturb the Curie- Weiss amplitude of the sample. The inference is that both magnetic and non-magnetic Mn sites be present in the quasicrystal and that iron can substitute only from among the latter. The simplest interpretation would be in terms of two 'classes' of Mn sites (one supporting a local moment, one not) although the possibility of there being more than one class of non- magnetic site cannot yet be excluded.