The effect of neutron irradiation on Nd-Fe-B and Sm/sub 2/Co/sub 17/-based high-temperature magnets

Results from the neutron irradiation experiments show that the radiation tolerance is very high for Sm/sub 2/Co/sub 17/-type magnets and is fairly low for Nd-Fe-B-type magnets. The analyses show that the major radiation damage in permanent magnets is caused by a radiation-induced thermal spike accompanied by a localized temperature T/sub L/, and the radiation tolerance of a magnet is determined mainly by its thermal stability. The T/sub L/ value depends on the radiation intensity and the magnet composition. The thermal stability of a magnet at temperature below its Curie temperature is related to its intrinsic coercivity H/sub ci/ and its shape.