The effect of Tb doping on the magnetic properties and microstructure of a TbNdFeCoB/Fe7Co3 nanocomposite permanent magnet

Abstract

Abstract Melt-spun NdFeB-type nanocomposite magnetic materials are important in a number of applications, including electromagnetic sensors, magnetic resonance imaging, and voice coil motors. Herein we investigated the magnetic properties and microstructures of melt-spun Tb x Nd10−x Fe80Co4B6/Fe7Co3 (x = 0.1, 0.2, and 0.3) ribbons by means of x-ray diffractometry, scanning electron microscopy, and magnetization experiments. Tb doping resulted in the formation of a 2:14:1 phase with a higher anisotropy field, which suppressed the separation of Fe7Co3 branch crystals and improved the magnetic properties of the material. Optimum magnetic properties that include a remanence (J r ) of 0.62 T, a coercivity (H ci ) of 612.0 kA m−1, and a maximum magnetic energy product ((BH)max) of 94.9 kJ m−3 were obtained for the annealed Tb0.3Nd9.7Fe80Co4B6/Fe7Co3 ribbon. Furthermore, the effective anisotropy constant, K e f f , and the saturation magnetization, M s , in the nanocomposite were determined by the LATS (law of approach to saturation) method. In this study, the values of K e f f and M s were found to lie between those of hard and soft magnetic phases, consistent with the exchange-coupling concept.