Increase of TC in UFe2+x synthesized by ultrafast cooling

The uranium Laves phase UFe2 was prepared by ultrafast cooling, which allows to incorporate excessive Fe of about 0.3 Fe/f.u. into the nanocrystalline Laves phase structure. 57Fe Mössbauer spectroscopy reveals that such Fe atoms occupy the U sites. Stronger magnetic hyperfine field points to larger Fe moments of such antistructure Fe. Higher Fe excess leads to its segregation in the form of α-Fe. The Curie temperature of the UFe2+x phase increases to the limit value 230–240 K.