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Abstract: Effect of elemental substitution of M (M=C, Cu, Ga, Al and Si) for Zr on the magnetic properties, phase evolution, and microstructure of melt spun Co80Zr18−x M x B2 (x=0–2) ribbons have been investigated. The x-ray diffraction (XRD) and thermal magnetic analysis (TMA) results showed that two magnetically soft phases, namely fcc-Co and Co23Zr6, coexisted with hard phase Co5Zr in Co80Zr17M1B2 ribbons with M=Cu, Ga, Al and Si, while an extra unknown magnetic phase was present in ribbons with M=C. The ribbons with M=C and Si were found to improve the remanence (σ r) of the Co80Zr17M1B2 ribbons. However, only M=Si could improve the whole magnetic properties, including B r, intrinsic coercivity (i H c) and energy product ((BH)max) of the above ribbons. The optimal magnetic properties of B r=5.2kG, i H c=4.5kOe, and (BH)max=5.3MGOe were obtained in Co80Zr17Si1B2 ribbons, which possessed Co5Zr and minor fcc-Co phases with much finer grain size (10–30nm) in comparison with its counterpart Co80Zr18B2 (20–60nm). [Copyright &y& Elsevier]

Magnetic properties, crystal structure, and microstructure of La 1-x Y x Co 4.7-y Fe y C 0.3 alloys (x = 0–1; y = 0–0.5) prepared by melt spinning are reported. Very low coercivity (i H c) of 0.2 kOe is found for LaCo 4.7 C 0.3 ribbon due to the existence of large amount of magnetically soft LaCo 13 (1:13) and La 2 Co 7 (2:7) phases. Interestingly, Y substitution for La was found effective in suppressing the formation of impurity phases and stabilizing 1:5 phase. Y entrance into 1:5 phase increases the Curie temperature and improves saturation magnetization (4πM s) and magnetocrystalline anisotropy field (H a), simultaneously. Fine microstructure observed for all studied samples due to C-doping contributes to high i H c and good squareness of demagnetization curve. The stabilized 1:5 phase and increased 4πM s with Y substitution for La and fine microstructure due to C-doping give rise to significant improvement of the permanent magnetic properties. The magnetic properties of LaCo 4.7 C 0.3 ribbons can be enhanced to remanence (B r) = 4.2–5.4 kG, i H c = 8.0–14.5 kOe, (BH) max = 3.6–6.6 MGOe for x = 0.25–1. Finally, for alloy with x = 0.5, Fe-doping could further improve magnetization and (BH) max of La 0.5 Y 0.5 Co 4.7-y Fe y C 0.3 ribbons, from B r = 4.4 kG and (BH) max = 4.4 MGOe for y = 0 to B r = 4.7–4.8 kG and (BH) max = 5.0–5.1 MGOe for y = 0.3–0.4, respectively. The result of this study provides a significant way to largely improve magnetic performance of isotropic LaCo 5 -based nanocomposites. • Magnetic properties and microstructure of LaCo 5 -based alloy prepared by melt spinning are reported for the first time. • A significant modification in phase constitutions with Y substitution for La remarkably improves the permanent magnetic properties of LaCo 4.7 C 0.3 ribbons. • Fe substitution for Co could further improve (BH) max of La 0.5 Y 0.5 Co 4.7 C 0.3 ribbon. • The improved (BH) max is related to strong exchange coupling effect between 1:5 and 1:13 phases due to fine grains. • The result suggests a useful way to improve the magnetic performance of isotropic LaCo 5 -based nanocomposites. [ABSTRACT FROM AUTHOR]