Magnetic Properties of Rare Earth Bonded Magnets

Abstract

There have been 3 types of powders for Rare Earth bonded magnets. They are 1/5 Sm-Co, 2/17 Sm-Co and Nd-Fe-B powders. The Nd-Fe-B bonded magnets are isotropic. For higher energy products anisotropic bonded magnets are required.
Examining the process parameters and evaluating additional elements, Nd₁₄Fe₇₉.₂₅B₆Ga_0.75 die upset magnet was developed as a starting material for anisotropic bonded magnets. The coercivity of die upset magnets after pulverizing is almost independent on the particle size. Anisotropic bonded magnets made from pulverized die upset magnets were developed. (BH).max values of 10 and 15 MGOe were obtained for injection and compression molded magnets, respectively. These magnets have enough thermal stability with irreversible losses under 5 % after exposure to 120°C(Pc=2).