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The doping effects of C and Sn on the magnetic properties, structure, and microstructure of melt spun YCo 5-x M x (M = C and Sn; x = 0–0.3) ribbons are studied. The permanent magnetic properties of B r  = 5.7 kG, i H c  = 1.8 kOe, and (BH) max  = 2.1 MGOe are obtained for the binary YCo 5 ribbon, and they are largely increased to B r  = 5.6–5.7 kG, i H c  = 7.0–14.7 kOe, (BH) max  = 5.3–6.5 MGOe for C-doping ribbons and B r  = 5.5–5.6 kG, i H c  = 5.2–14.4 kOe, (BH) max  = 3.8–6.2 MGOe for Sn-doping ribbons, respectively. All studied ribbons mainly consist of hexagonal 1:5 phase with space group of P6/mmm. The entrance of C or Sn into the crystal structure of 1:5 phase modifies lattice constants and increases Curie temperature. The microstructure is effectively refined from 100 to 300 nm for binary ribbons to 10–50 nm for C-doping and 60–100 nm for Sn-doping ribbons, respectively. For high Sn-content YCo 4.7 Sn 0.3 ribbon, Y 5 Sn 3 precipitates with 10–20 nm in diameter form in the matrix, and these nonmagnetic phase may act as a pinning site to impede magnetization reversal and thus contribute to enhance coercivity. Magnetic property enhancement with C-doping is attributed to the formation of Y(Co, C) 5 phase and microstructure refinement, while one with Sn-doping is related to the formation of Y(Co, Sn) 5 phase, microstructure refinement, and the induction of nonmagnetic Y 5 Sn 3 precipitates. [ABSTRACT FROM AUTHOR]

Magnetic properties of melt spun Co 86.5 Hf 10.5 MB 2 ribbons with refractory elements substitution (M=Cr, Nb, Ti, Zr) have been studied. For ternary Co 86.5 Hf 11.5 B 2 ribbon, permanent magnetic properties of B r =0.71 T, i H c =192 kA/m, and (BH) max =34.4 kJ/m 3 are obtained, and they are significantly improved to B r =0.73–0.76 T, i H c =136–216 kA/m and (BH) max =38.4–52.8 kJ/m 3 with M substitution. Summarized with the results of x-ray diffraction refinement, thermal magnetic analysis, and transmission electron microscopy, the Co 86.5 Hf 10.5 MB 2 nanocomposites following the optimal crystallization treatment mainly consist of orthorhombic 7:1 and face-center-cubic Co phases. Fine microstructure with average grain size in the range of 12.5−19.6 nm promotes exchange coupling effect between magnetic grains, thus improving permanent magnetic properties. The magnetic field dependence of coercivity reveals that coercivity of the studied Co 86.5 Hf 10.5 MB 2 nonocomposites is mainly governed by the reverse domain nucleation mechanism. [ABSTRACT FROM AUTHOR]

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]

The magnetic properties, phase evolution, microstructure, and magnetic domain structure of melt-spun PrCo 5- x C x and PrCo 5 C y (x = 0–0.4 and y = 0–0.4) flakes are compared. Binary PrCo 5 flakes exhibit low intrinsic coercivity (i H c) of 3.2 kOe and thus a low magnetic energy product ((BH) max) of 4.4 MGOe, which is attributed to the coarse grains. By doping with proper amounts of C, the well-modified phase composition and uniformly refined microstructure and magnetic domains enhance the magnetic properties remarkably. Different phase compositions found for two approaches for doping PrCo 5 with C dominate the magnetic properties in addition to the fine microstructure. In PrCo 5- x C x (x = 0–0.4) flakes, the 2:17 phase suppressed by doping with C contributes to coercivity increase, and the largest i H c of 13.5 kOe with (BH) max = 8.8 MGOe is obtained for PrCo 4.9 C 0.1 flakes. For higher x , the formation of the 5:19 phase slightly reduces i H c to 7.2–8.8 kOe and (BH) max to 7.2–8.0 MGOe. In contrast, in the PrCo 5 C y (y = 0–0.4) series flakes, the increased amount of the 2:17 phase and the strengthened exchange coupling effect resulting from the refined microstructure caused by doping with a proper amount of C result in large (BH) max of 11.8 MGOe with i H c of 5.0 kOe for PrCo 5 C 0.3 flakes. • C doping significantly improves the magnetic properties of melt-spun PrCo 5 flakes. • C doping refines the sizes of the grains and magnetic domains. • Different phase compositions for two approaches for C doping dominate the magnetic properties. • In PrCo 5- x C x , the suppressed 2:17 phase resulting from doping with C contributes to high intrinsic coercivity. • In PrCo 5 C y flakes, the 2:17 phase well coupled with the 1:5 phase results in high (BH) max. [ABSTRACT FROM AUTHOR]