Magnetic hardening of melt-spun nanocomposite Nd₂Fe₁₄B/Fe magnets

Authors

I. Panagiotopoulos, Department of Physics and Astronomy, University of Delaware, Newark, Delaware
L. Withanawasam, Department of Physics and Astronomy, University of Delaware, Newark, Delaware
A.S. Murthy, Department of Physics and Astronomy, University of Delaware, Newark, Delaware
George C. Hadjipanayis, University of DelawareFollow
E.W. Singleton, University of Nebraska - Lincoln
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

4-15-1996

Comments

Published by American Institute of Physics. J. Applied Physics 79, 4827 (1996). ©1996 American Institute of Physics. Permission to use. http://jap.aip.org/jap/.

Abstract

Coercivity optimization studies were done on melt-spun nanocomposite Nd₄R₂Fe_87-xNbT_xB₆ (R=Nd,Y,Dy; T=Ag,Cu) isotropic ribbon samples. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties [H_c=3.9 kOe, (BH) _max=10 MGOe] were obtained by annealing at 750–775 °C for a few minutes. Optimization by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted grain size for optimum coupling between the hard and the soft phase. With the annealing conditions used, Nd₄Dy₂Fe₈₇NbB₆ samples gave moderate coercivities and in Nd₄Dy₂Fe₈₇NbB₆ samples the coercivity was reduced more than the expected reduction in the anisotropy field due to the presence of Y.