Effect of boron content on the magnetic properties, phase evolution, and microstructure of Pr9Fe88.5-xTi2.5Bx (x=7-15) nanocomposites

The magnetic properties, phase evolution, and microstructure of melt-spun Pr₉Fe_88.5-xTi_2.5B_x(x=7 to 15) nanocomposites have been investigated. From thermal magnetic analysis (TMA), the volume fraction of Pr₂Fe₁₄B phase increases and α-Fe phase decreases with increasing x, giving rise to the increment of _iH_c and the decrement of B_r. But the average grain size of the ribbons is slightly decreased with the increment of boron content x, from 15-30 nm for x=7 to 10--20 nm for x=15. As a result, the optimum magnetic properties of B_r=9.5 kG, _iH_c=10.8 kOe, and (BH)_max=17.8 MGOe can be achieved in Pr₉Fe_bal.Ti_2.5B₁₁. In addition, further substituting Co for Fe in Pr₉Fe_77.5-yCo_yTi_2.5B₁₁ ribbons not only increases the Curie temperature of magnetic phases 2:14:1 and α-Fe, but also improves the thermal stability of the ribbons. Higher magnetic properties of B_r=9.7 kG, _iH_c=11.3 kOe, and (BH)_max=18.5 MGOe are obtained in Pr₉Fe_67.5Co₁₀Ti_2.5B₁₁ ribbons.