Evolution of magnetic properties and microstructure of Hf{sub 2}Co{sub 11}B alloys

Journal Article · Sat Feb 07 00:00:00 EST 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4907575· OSTI ID:22413044

Rios, Orlando ^[1]

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1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

Amorphous Hf{sub 2}Co{sub 11}B alloys produced by melt-spinning have been crystallized by annealing at 500–800 °C, and the products have been investigated using magnetization measurements, x-ray diffraction, and scanning electron microscopy. The results reveal the evolution of the phase fractions, microstructure, and magnetic properties with both annealing temperature and time. Crystallization of the phase denoted HfCo{sub 7}, which is associated with the development of coercivity, occurs slowly at 500 °C. Annealing at intermediate temperatures produces mixed phase samples containing some of the HfCo{sub 7} phase with the highest values of remanent magnetization and coercivity. The equilibrium structure at 800 °C contains HfCo{sub 3}B{sub 2}, Hf{sub 6}Co{sub 23}, and Co, and displays soft ferromagnetism. Maximum values for the remanent magnetization, intrinsic coercivity, and magnetic energy product among the samples are approximately 5.2 kG, 2.0 kOe, and 3.1 MGOe, respectively, which indicates that the significantly higher values observed in crystalline, melt-spun Hf{sub 2}Co{sub 11}B ribbons are a consequence of the non-equilibrium solidification during the melt-spinning process. Application of high magnetic fields during annealing is observed to strongly affect the microstructural evolution, which may provide access to higher performance materials in Zr/Hf-Co hard ferromagnets. The crystal structure of HfCo{sub 7} and the related Zr analogues is unknown, and without knowledge of atomic positions powder diffraction cannot distinguish among proposed unit cells and symmetries found in the literature.

• OSTI ID: 22413044
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMORPHOUS STATE
ANNEALING
APPROXIMATIONS
BORON ADDITIONS
COBALT BASE ALLOYS
COERCIVE FORCE
CRYSTAL STRUCTURE
CRYSTALLIZATION
FERROMAGNETISM
HAFNIUM ALLOYS
MAGNETIC FIELDS
MAGNETIC PROPERTIES
MAGNETIZATION
MICROSTRUCTURE
POWDERS
SCANNING ELECTRON MICROSCOPY
SOLIDIFICATION
X-RAY DIFFRACTION