Temperature dependences of structure and coercivity for melt-spun MnBi compound

• Published in: Journal of magnetism and magnetic materials Vol. 330; pp. 106 - 110
• Main Authors: Yang, Y.B., Chen, X.G., Guo, S., Yan, A.R., Huang, Q.Z., Wu, M.M., Chen, D.F., Yang, Y.C., Yang, J.B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2013; Elsevier
• Subjects: Anisotropy; Coercive force; Coercivity; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Lattice constant; Lattice parameters; Magnetic anisotropy; Magnetic moment; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Magnetization; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Melt spinning; MnBi; Physics; Ribbons; Temperature dependence; Lattice constant; MnBi; Coercivity; Magnetic moment; Particle size; Annealing; Magnetization; Phase transformations; Magnetic moments; Melt spinning; Magnetic hysteresis; XRD; Lattice parameters; Magnetic anisotropy; Coercive force; Manganese alloys; Bismuth alloys; Chemical composition; Transition element alloys
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2012.10.046

Low temperature phase MnBi compound was prepared by annealing the melt-spun amorphous MnBi ribbons. Temperature dependences of structure, magnetization and coercivity were investigated using neutron/X-ray powder diffraction and magnetic measurements. It is found that the lattice parameter c/a ratio of the MnBi increases with the increasing temperature and finally reaches a maximum of 1.433 around 600K. No structural phase transition is observed at 633K. Especially, the lattice constants of MnBi at 700K are a=b=4.30919Å, and c=6.17521Å, which are not in accordance with the previous data for bulk MnBi. Magnetic moment of Mn atom tends to lie in the ab-plane at 10K, and turns to align along c-axis around 90K. The growth of LTP MnBi grains is observed above 500K, which increases the content of MnBi. The coercivity of MnBi shows a positive temperature coefficient, reaches a maximum of 2.5T at 540K, and decreases to 1.8T at 610K. The temperature dependence of the coercivity is related to the change of magnetocrystalline anisotropy, and shows strong dependence on the sizes of MnBi particles. ► MnBi compound was investigated by neutron/X-ray powder diffraction and magnetic measurements. ► c/a lattice parameter ratio of the MnBi increases with the increasing temperature. ► No structural phase transition is observed for nanoscale MnBi at 633K. ► Temperature dependence of the coercivity is studied.