Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

[1]  E. Choi,et al.  Change of the equilibrium state of ferromagnetic MnBi by high magnetic fields , 2011 .

[2]  Tie Liu,et al.  Effects of a high magnetic field on the coarsening of MnBi grains solidified from isothermal annealed semi-solid melt , 2010 .

[3]  Jiuxing Zhang,et al.  Microstructure and magnetic properties of isotropic bulk NdxFe94−xB6 (x=6,8,10) nanocomposite magnets prepared by spark plasma sintering , 2006 .

[4]  Samit Roy,et al.  Structure and magnetic properties of the MnBi low temperature phase , 2002 .

[5]  B. Slusarek,et al.  Application of permanent magnets made from NdFeB powder and from mixtures of powders in DC motors , 2002 .

[6]  A. Bollero,et al.  Magnetic properties of the MnBi intermetallic compound , 2001 .

[7]  S. Simizu,et al.  Magnetic properties of MnBi1−xRx (R=rare earth) systems , 2000 .

[8]  John Ormerod,et al.  Bonded permanent magnets: Current status and future opportunities (invited) , 1997 .

[9]  J. Schneider,et al.  Bonded hybrid magnets , 1996 .

[10]  Guo,et al.  Magnetic properties of MnBi prepared by rapid solidification. , 1992, Physical review. B, Condensed matter.

[11]  A. Załuska,et al.  The formation of single-phase equiatomic MnBi by rapid solidification , 1990 .

[12]  M. Kishimoto,et al.  Temperature Dependence of Coercivity of MnBi Particles , 1975 .

[13]  W. Stutius,et al.  The phase transformation and physical properties of the MnBi and Mn 1.08 Bi compounds , 1974 .

[14]  T. Chen.  Contribution to the equilibrium phase diagram of the Mn–Bi system near MnBi , 1974 .

[15]  H. Zijlstra,et al.  Structural and Magnetic Properties of a Bi–MnBi Composite , 1968 .

[16]  L. Ehrenberg,et al.  The Magnetic and Crystallographic Properties of MnBi Studied by Neutron Diffraction. , 1967 .

[17]  B. W. Roberts.  Neutron Diffraction Study of the Structures and Magnetic Properties of Manganese Bismuthide , 1956 .

[18]  W. Hubbard,et al.  A New Permanent Magnet from Powdered Manganese Bismuthide , 1952 .

[19]  Charles Guillaud.  Les rotations dans l'aimantation (aimantation initiale, champ coercitif) , 1951 .