A permanent magnet with good thermal stability has a compsn. given by the general formula R(Fe1-x-y-zCoxByGaz)A, where R is Nd alone or one or more rare earth elements, pref. Nd, Pr, or Ce, 0~x~0.7, 0.02~y~0.3, 0.001~z~0.15, and 4.0~A~7.5. Most pref., the amt. of Co is 0.05 to 0.25, the amt. of Ga is 0.005 to 0.05, the amt. of B is 0.04 to 0.015, and A is in the range 5.0 to 6.8. In addn. the permanent magnet may contain one or more elements selected from Nb, W, V, Ta, and Mo. A permanent magnet of the invention is conveniently made by known methods of powder metallurgy, rapid quenching, or resin bonding.
USE/ADVANTAGE -Addn. of Ga or a combination of Ga and Co provides rare earth-iron-boron permanent magnets with high coercive force together with high Curie temp. and thus highly improved thermal stability compared with known magnets in the rare earth-iron-boron system.
