Magnetic behaviour of rapidly quenched Nd-Dy-Fe-B alloys

The effects of wheel speed on the magnetic properties of melt-spun Nd/sub 13.5/Dy/sub 3.7/Fe/sub 75/B/sub 7.8/ alloys are investigated. Structural characterization is carried out by X-ray diffraction and scanning electron microscopy. Thermal demagnetization is studied by thermomagnetic analysis. The as-quenched samples show the Curie temperature of an amorphous phase around 460 K besides the T/sub c/ of the Nd/sub 2/Fe/sub 14/B/sub 1/ phase at T/sub c/=589 K. Hysteresis loops are measured with a vibrating sample magnetometer (VSM) with applied fields up to 2 T at room temperature. A dip in the second quadrant of the hysteresis loops confirms the presence of an amorphous phase in the samples quenched at high speeds. After annealing the samples at 875 K for 4 minutes, the coercivity for the sample spun at 23 m/s increases from 0.5 T to 1.55 T.