Recent development in sintered and bonded rare earth magnets

The paper concentrates on the development in NdFeB-type magnets. There has been a rapid growth in the production of sintered magnets based on the ferromagnetic phase Nd₂Fe₁₄B and spectacular growth for the bonded magnets based on the melt-spun material. The paper describes the production methods required to manufacture the high (BH)max magnets. The bonded NdFeB magnet market has been dominated by the MagneQuench melt-spun ribbon material and this is still a vital ingredient in the production of these magnets. The worrying feature however is that this raw material is still "singly sourced". However, there may now be an alternative in the form of the HDDR-type powder which can be either isotropic or anisotropic. The production of this material is described and its characteristics are compared with those of the MQ-powder