Magnetic Properties and Crystal Structures of Nd-Fe-Co-B System Permanent Magnets

Several experimental studies have been carried out recently on the magnetic properties of Nd-Fe-B alloys. In this paper, we report on the effects of partial substitution of cobalt for iron in the Nd-Fe-B system. The samples prepared by powder metallurgical methods were of the composition Nd23-yFe77-2xCO2xBy, where x = 0 to 10 and y = 5 to 10. We have obtained significant improvement in the Curie temperature by increasing the cobalt content in the alloy system. The temperature coefficient ¿r of the Nd16Fe66Co11B7 is about -0.02 percent/°C, in the temperature range 20 to 100°C, compared with -0.03 percent/°C for Nd-Fe-B samples. We developed a magnet in the Nd-Fe-Co-B system with a maximum energy product of 41 MGOe.