Anisotropic Nd-Fe-B melt-spun magnets

The effect of quench rate in terms of the circumferential wheel speed and temperature of the melt when ejected on crystallographic orientation were studied for Nd-Fe-B melt-spun magnets. It was found that the temperature of the melt (T_m) is the dominant parameter affecting the preferred orientation of the tetragonal Nd₂Fe₁₄B compounds. When T_m was increased up to 1400°C, it was confirmed by X-ray diffractometry that the c-axis was oriented normal to the ribbon plane on the free surface. The c-axis orientation was also available on the directly quenched wheel surface by increasing the T_m up to 1600°C. Both surfaces of these ribbons exhibited maze domain patterns due to c-axis orientation. Magnetic measurements revealed that the remanence measured in the direction normal to the ribbon plane was small compared to expected values, which is presumably because of the coarse grain size due to the high T_m