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The effect of titanium addition on the structure and magnetic properties was studied for the nanocomposite Nd 7 Fe 79-x B 14 Ti x and Nd 8 Fe 78-x B 14 Ti x systems. The alloys were rapidly solidified by melt-spinning with the roll speed 20 m/s. The overquenched, amorphous ribbons were subsequently crystallization annealed for 20 min at 953-973 K. It was found that the addition of 2 and 4 at% of Ti leads to a substantial increase of the coercivity and maximum energy product of the nanocomposite magnets while maintaining the remanence unchanged. The highest properties were obtained for the alloys containing 4 at% of Ti. The maximum energy product of 143 kJ/ m 3 was achieved for the Nd 8 Fe 74 B 14 Ti 4 alloy. The TEM studies showed substantial differences in the morphology of the alloys. The ternary alloys contain grains of various sizes of approximately 300 nm. The alloys containing 4 at% of Ti exhibit more homogeneous structure with the crystal sizes up to 30 and 50 nm for the Nd 8 Fe 74 B 14 Ti 4 and Nd 7 Fe 75 B 14 Ti 4 alloys, respectively. More detailed information on the phase constitution was obtained from the Mössbauer spectroscopy. Comparison of the Ti-free and 4 at% Ti alloys revealed that the amount of the hard magnetic Nd 2 Fe 14 B phase decreases from 84.53 to 69.88% for the Nd 7 Fe 79-x B 14 Ti x system and increased from 66.60 to 82.48% for Nd 8 Fe 78-x B 14 Ti x system.

The influence of Nb doping was studied on ribbons of nominal composition Nd Fe B Nb . The alloys were prepared by melt-spinning and then annealed at 973 K for 20 minutes. The magnetic characterization revealed that niobium addition improves substantially the magnetic properties of the studied alloys. The structural characterization showed that, in most alloys, the magnetically hard phase Nd Fe B precipitated as the main phase. This was not the case for the ternaries and for the Nd Fe B Nb alloys. Furthermore, the addition of Nb inhibited the precipitation of -Fe, independently of the Nd content. From the complete set of samples studied in this work, we found that the sample with nominal composition Nd Fe B Nb exhibited the highest coercive field kA/m while Nd Fe B Nb showed the highest maximum energy product, kJ/m .