Rfeb-based magnet production method, rfeb-based magnet, and coating material for grain boundary diffusion process

The present invention addresses the problem of providing an RFeB-based magnet production method that enables coercivity to be increased, without a coating material peeling from substrate surfaces during a grain boundary diffusion process. This method for producing an RL 2Fe14B-based magnet, which is a sintered magnet or a hot plastic-worked magnet containing a light rare earth element (RL) comprising neodymium and/or praseodymium as a main rare earth element, involves applying, to the surfaces of a substrate (M) of the RL 2Fe14B-based magnet, a coating material (10) obtained by mixing a silicone grease (11) and an RH-containing powder (14), which contains a heavy rare-earth element (RH) comprising at least one of dysprosium, terbium and holmium, and heating the substrate (M) for each coating material (10) layer. Since silicone has a siloxane bond, the coating material (10) can be prevented from peeling from the surfaces of the substrate (M) during heating. Furthermore, the adhesion of the coating material (10) to the substrate (M) increases, allowing the RH to easily move to the grain boundaries of the substrate (M), thus enabling coercivity to be increased.