Investigation of the U(Fe 10−xCo x)Si 2 ternary system with 0 ≤ x ≤ 10 by X-ray powder diffraction, magnetic and 57Fe Mössbauer studies

Abstract

The UFe 10Si 2 and UCO 10Si 2 silicides crystallize in the tetragonal ThMn 12-type structure but with different silicon distributions in the crystallographic sites. The Rietveld X-ray diffraction study indicates that in both compounds the silicon is distributed between the 8f and 8j sites in different proportions: (i) for UFe 10Si 2, 75% of the silicon atoms are in 8f site and 25% in the 8j site; (ii) for UCo 10Si 2, nearly all the silicon atoms (>90%) are in the 8f site. These silicides exhibit a ferromagnetic ordering below (640±10) K (UFe 10Si 2) and (510±10) K (UCo 10Si 2). For the U(Fe 10− x Co x )Si 2 solid solution, the Curie temperature increases progressively and goes through a maximum for x ≈ 5 ( T C = (750±10) K) with rising cobalt content. The 57Fe Mössbauer spectroscopy study indicates that the cobalt, substituted for iron, is not randomly distributed in the 8f, 8i and 8j sites.