Recent progress in the development of nanophase rare earth magnets

Nanocrystalline melt-spun rare earth - iron - boron alloys based on Pr and on Nd-Pr mixtures have been studied. Their magnetic properties are compared with those of corresponding alloy ribbons based on Nd. The Pr containing alloys have gener-ally higher coercivity than their Nd counterparts because of the higher anisotropy constant of the Pr2Fe14B phase. Co substitution for Fe increases the Curie tem-perature for both the Pr and Nd-Pr nanophase alloys. excellent magnetic property combinations were achieved for single phase Pr12(Fe100-xCox)82B6 (x = 0 - 20) alloys, processed by overquenching and devitrification annealing. Addition of 1 at % Zr as a grain refiner resulted in increased coercivity and maximum energy product of NdPrFeB alloys for the whole range of RE contents studied (8 - 12 at %).