EN
Two sets of Fe_{52-x}Co_{x}Pt_{28}B_{20} (x=0-26 at.%) and Fe_{60-x}Co_{x}Pt_{25}B_{15} (x=0-40 at.%) alloys were prepared in the form of ribbons by the rapid quenching technique. Structure of the samples was characterized by Mössbauer spectroscopy and X-ray diffraction. In the as-quenched alloys the amorphous phase coexisted with the fcc-(Fe,Co)Pt disordered solid solution. Differential scanning calorimetry measurements performed in the range 50-720 °C revealed one or two exothermal peaks. The magnetically hard ordered L1_{0} (Fe,Co)Pt and magnetically soft (Fe,Co)_{2}B nanocrystalline phases were formed due to thermal treatment of the alloys. The influence of Co content on the structure of the as-quenched and heated alloys was studied.