Abstract
Anisotropic Nd-(Fe, Co)-B-M(M=Ga, Hf, Zr, Al, Zn, Nb, Ta, Dy and Fe) magnets were prepared by melt-spinning and hot deformation (die-upsetting). Intrinsic coercivity and irreversible loss are dramatically improved when Ga is added. Ga is condensed in a boundary phase (1 nm in thickness) and a Nd-rich phase. Ga seems to strengthen the pinning force of domain walls at grain boundaries. Addition of Ga and substitution of Co improved the coefficient of remanence and the irreversible loss.
Permanent magnet properties obtained for Nd14FebalCo15B6Ga0.75 are as follows: Br=1.20 T, iHc=1.66 MA/m, bHc=0.92 MA/m, (BH)max=274 kJ/m3. Temperature coefficient of Br is −0.067%/K (average value between 298 and 423 K) and an irreversible loss after exposure up to 453 K is 3.2% (B⁄H=−2).
