Elemental effect on the TbCu_7-type melt spun Sm(Co, M)_7 (M= Hf, V, Nb, Ta, Cr, Mo, Al, Si, Ge, and Sn) ribbons have been investigated systematically. SmCo_(7-x)M_x (M=Hf, V, Nb, Ta, Al, Si, Ge and Sn) ribbons spun at a high wheel speed of 40 m/s crystallize in the TbCu_7-type structure. The XRD results, analyzed by the Rietveld refinement method, show that Hf, V, Nb, Ta, Cr, Mo, Ge, and Sn prefer to occupy the 2e site in the TbCu_7-type structure, whereas Al and Si prefer to occupy the 3g site in the TbCu_7-type structure. The grain size of the above ribbons is almost unchanged with a slight elemental substitution, the increase of coercivity is mainly resulted from the magnetocrystalline anisotropy enhancement. Nevertheless, for the ribbons with M=V, Cr, Mo, Si and Sn, further increase of the substituted element content x, grain size refinement could also contribute the increase of coercivity. The highest_iH_c of 19 kOe can be attained for SmCo_(6.5)Hf_(0.5), while the optimal magnetic properties of B_r= 6.4 kG,_iH_c≈7.3 kOe and (BH)_(max)=8.7 MGOe are obtained for SmCo_(6.9)Hf_(0.1) alloy ribbons.
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