Improvement on the magnetic properties of Pr8.5Fe81.5B10 nanocomposites by refractory elements substitution

The magnetic properties and phase evolution of Pr-lean and boron-enriched Pr_8.5Fe_79.5M₂B₁₀ (M = Cr, Nb, V, Ti, and Zr) melt-spun ribbons have been studied. Based on thermal magnetic analysis (TMA), a slight substitution of the selected refractory elements (Cr, Nb, V, Ti, and Zr) for Fe in Pr_8.5Fe_79.5M₂B₁₀ not only suppresses the formation of metastable Pr₂Fe₂₃B₃ and Fe₃B phases but also leads to the presence of large amount of Pr₂Fe₁₄B and α-Fe phases of fine grain size (<30 nm). Exchange coupling effect is found to exist in all nanocomposites, which is attributed to their finer grain size if suitable crystallization treatment is employed. As a result, the magnetic properties of the ribbons are improved remarkably. The optimum magnetic properties of B_r=9.6 kG, _iH_c=8.5 kOe, and (BH)_max=17.8 MGOe are achieved in Pr_8.5Fe_79.5Ti₂B₁₀, while the highest coercivity of _iH_c=9.9 kOe (B_r=9.2 kG and (BH)_max=16.9 MGOe) is obtained in Pr_8.5Fe_79.5Nb₂B₁₀.