New NdFeB-based bulk "exchange spring"-type permanent magnets. Experimental and micromagnetic FORC analysis

Summary form only given. This paper focuses on the possibility of direct casting miniature NdFeB-based bulk permanent magnets in different three-dimensional shapes for various applications, with amorphous structure followed by subsequent optimal annealing. Nd
₃
Dy
₁
Fe
₆₆
Co
₁₀
B
₂₀
bulk nanocomposite permanent magnets in form of rods with diameters ranging from 0.5 to 0.8 mm have been prepared by devitrification annealing of amorphous and partly-amorphous precursors produced by injection die-casting. A fully amorphous structure was obtained for rods with the diameter as large as 0.6 mm. The best-achieved magnetic properties have been obtained for the optimum devitrification (15 min at 630degC) samples with 0.6 mm diameter, and are: H
_C,5T
= 316 kA/m, mu
₀
M
_r,6T
= 1.04 T, M
_r
/M
_max,6T
=0.68 and (BH)
_max,6T
=98 kJ/m
³
. The samples were characterized using the first-order reversal curve diagram (FORC). The micromagnetic simulation reproduced the experimental results.