The structural and magnetic properties of nanocomposite melt-spun Sm(Co{sub}(0.74-x)Fe{sub}0.1Cu{sub}0.12Zr{sub}0.04B{sub}x){sub}7.5 magnets have been investigated as a function of boron content (x = 0.005 -0.05), wheel speed and annealing conditions. The as-spun ribbons are nanocrystalline with fine microstructure and average grain size of 60-100 nm. X-ray diffraction indicates that the as-spun samples have the metastable hexagonal TbCu{sub}7 -type structure phase and fcc-Co as a secondary soft phase. Magnetization at nonsaturating 5 T field is 45-72 emu/g and the reduced remanence (Mr/Ms) is above 0.8. The loop shape exhibits a characteristic step due to the soft magnetic phase. At room temperature, He values of 20-28 kOe are obtained for as spun samples, with a record value of 38.5 kOe for x = 0.04. At 380 ℃ He, values higher than 5 kOe are observed. Coercivity and loop shape are strongly dependent on annealing conditions.
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