Crystal structure and magnetic properties of americium laves phases

An investigation was made of a series of binary americium alloys with AB2 stoichiometry (B = Al, Co, Fe, Rh and Ru) prepared from the 243Am isotope. The C-15 (MgCu2-type) structure appears in AmAl2, AmCo2, AmFe2, and AmRh2, whereas AmRu2 is isostructural with AmOs2 which has the C-14 (MgZn2-type) structure. The magnetic properties of the cubic americium laves phases were studied by means of magnetization and nuclear gamna-ray resonance (Moessbauer effect) measurements between 2.5 and 3000K. All the cubic Laves phases studied, except AmFe2, exhibit almost temperature-independent paramagnetism. The AmFe2 sample is ferromagnetic with an estimated Curie temperature of approximately 4000K. The hyperfine field at the Am site in all the compounds is small. The bulk magnetic moment of AmFe2 (approximately 3 μ/sub B//F.U.) is thus associated only with the Fe atoms. The magnetic properties of the compounds are consistent with the assumption that the Am ion is in the +3 state (5f6)