Partitioning of Co upon nanocrystallization of soft magnetic FeCo(Zr, Nb)B alloys - a 59Co NMR study.

59Co NMR spectroscopy has been used to monitor structural modifications of (Fe0.5Co0.5)89Zr7B4 and (Fe0.25Co0.75)81Nb7B12 amorphous ribbons subject to different heat treatments. The characteristic features of 59Co NMR spectra in the as-cast samples indicate a compositional modulation of (Fe0.25Co0.75)81Nb7B12, whereas (Fe0.5Co0.5)89Zr7B4 ribbon is more homogenous, indicating, however, a slight preference to form Co78Zr22-like environments. Upon heat treatment, a precipitation of an ordered (B2) CoFe crystalline phase is observed in both systems.