Effect of boron content on the magnetic properties, phase evolution, and microstructure of Pr/sub 9/Fe/sub 88.5-x/Ti/sub 2.5/B/sub x/ (x=7-15) nanocomposites

Abstract

The magnetic properties, phase evolution, and microstructure of melt-spun Pr/sub 9/Fe/sub 88.5-x/Ti/sub 2.5/B/sub x/(x=7 to 15) nanocomposites have been investigated. From thermal magnetic analysis (TMA), the volume fraction of Pr/sub 2/Fe/sub 14/B phase increases and /spl alpha/-Fe phase decreases with increasing x, giving rise to the increment of /sub i/H/sub c/ and the decrement of B/sub 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/sub r/=9.5 kG, /sub i/H/sub c/=10.8 kOe, and (BH)/sub max/=17.8 MGOe can be achieved in Pr/sub 9/Fe/sub bal./Ti/sub 2.5/B/sub 11/. In addition, further substituting Co for Fe in Pr/sub 9/Fe/sub 77.5-y/Co/sub y/Ti/sub 2.5/B/sub 11/ ribbons not only increases the Curie temperature of magnetic phases 2:14:1 and /spl alpha/-Fe, but also improves the thermal stability of the ribbons. Higher magnetic properties of B/sub r/=9.7 kG, /sub i/H/sub c/=11.3 kOe, and (BH)/sub max/=18.5 MGOe are obtained in Pr/sub 9/Fe/sub 67.5/Co/sub 10/Ti/sub 2.5/B/sub 11/ ribbons.