Publication Date:
2014-11-13
Description:
Hard magnetic property enhancement of melt spun Co 88 Hf 12 ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH) max ) of 2.6 MGOe and intrinsic coercivity ( i H c ) of 1.5 kOe for B-free Co 88 Hf 12 ribbons to (BH) max = 7.7 MGOe and i H c = 3.1 kOe for Co 85 Hf 12 B 3 ribbons but also improve the Curie temperature (T C ) of 7:1 phase. The (BH) max value achieved in Co 85 Hf 12 B 3 ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher than that of Co 11 Hf 2 B ribbons spun at 16 m/s [M. A. McGuire, O. Rios, N. J. Ghimire, and M. Koehler, Appl. Phys. Lett. 101 , 202401 (2012)]. The structural analysis confirms that B enters the orthorhombic Co 7 Hf (7:1) crystal structure as interstitial atoms, forming Co 7 HfB x , in the as-spun state. Yet B may diffuse out from the 7:1 phase after post-annealing, leading to the reduction of Curie temperature and the magnetic properties. The uniformly refined microstructure with B-doping results in high remanence (B r ) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co 7 HfB x phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co 7 Hf-based ribbons.
Print ISSN:
0003-6951
Electronic ISSN:
1077-3118
Topics:
Physics
