Controlling the properties of high energy density permanent magnetic materials by different processing routes

This article addresses the most recent developments in the processing of high-performance magnets based on rare earth-transition metal (R-T) compounds. It gives an overview of the relevant classes of R-T compounds together with a description of the appropriate manufacturing route and an assessment of their potential for application. The paper pays particular attention to state-of-the-art maximum energy density and high-temperature magnets as well as to the synthesis of nanostructured materials using non-equilibrium techniques and reversible hydrogen-induced phase transformations. The possibilities of increasing the energy density of the nanocrystalline magnets by remanence enhancement utilizing intergranular exchange coupling, by texturation via hot deformation or by hydrogenation disproportionation desorption and recombination to produce anisotropic powders are discussed.