The addition of 1 at.% of Zr to (Pr,Dy)_x(Fe,Co)_80-xB₂₀ type alloys (x up to 4.5 at.%) led to significant improvement of their glass forming abilities, so that amorphous 1mm dia. rods and thin walled tubes having outer diameters up to 4 mm could be produced. Subsequent annealing of the amorphous samples resulted in formation of a nanocrystalline structure containing soft magnetic Fe₃B, and the hard magnetic (Pr,Dy)₂(Fe,Co)₁₄B phases. However, the low concentration of the RE elements, together with the detrimental effect of Zr on the magnetic properties, resulted in relatively low values of coercivity _JH_c and of (BH)_max for the alloys investigated. Recently, for as-cast Nd-Fe-B-type ribbon samples with Nd contents of ~9 at. % and high boron contents of ~15 at. %, significant coercivities were demonstrated. This has stimulated the present investigation of the processing of hard magnetic nanocrystalline bulk samples with improved magnetic properties. Nanocrystalline Fe-Co-Pr-B-Ti-Zr alloy rods of diameter 1 mm and tubes of outer diameter 3 mm, were produced by die casting. Good enhancement of remanence J_r to values>0.6J_s, in combination with unusually high μ_{0 J}H_c of ~0.65T, were achieved for samples in the as-cast state. Subsequent annealing of the samples at various temperatures led to even better hard magnetic properties (i.e.μ_{0 J}H_c increased to ~1T for samples annealed at 300^oC for 30 min).

Work supported by Polish Scientific Research Committee (KBN)(projects no. 3T08A 063 27 and 3T08C 008 28) and by the U.K. Engineering and Physical Sciences Research Council.

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