59Co NMR study of nanocrystallization process in Co-rich HITPERM (Fe0.25Co0.75)Nb7B12 alloy

59Co NMR spectroscopy has been used to monitor structural modification of (Fe_0.25Co_0.75)₈₁Nb₇B₁₂ amorphous ribbon subjected to heat treatment at 450C. The characteristic features of 59Co NMR spectra in the as-cast samples indicate a compositional modulation of (Fe_0.25Co_0.75)₈₁Nb₇B₁₂. Upon heat treatment, a precipitation of an ordered CoFe crystalline phase (deriving from B2 order) is observed. A strong tendency for higher Fe content in the nanocrystalline phase than the nominal composition of the amorphous precursor has been observed.