Effect of Ga substitution on the structure and magnetic properties of melt-spun Pr3(Fe,Co,Ti)29 system

Melt-spun alloys of Pr-3(Fe0.7Co0.3)(27.5)Ti-1.5, Pr-3(Fe0.6Co0.4)(27.5)Ti-1.5, and Pr-3(Fe0.5Ga0.1Co0.4)(27.5)Ti-1.5 prepared at linear wheel speeds of 20, 30, and 40 m/s were found to contain nanocrystalline, a mixture of nanocrystalline and amorphous, and mostly amorphous phases, respectively. Grain sizes of < 10 nm were observed for the crystalline phases. Annealed alloys showed an increase in grain size to 15-20 nm. The Curie temperature (T-C) values observed in melt-spun alloys were lower than those observed in fully crystalline alloys. A reduction of similar to 55 degrees C in T-C was observed for the Pr-3(Fe0.7Co0.3)(27.5)Ti-1.5 composition compared to similar to 15 degrees C for Pr-3(Fe0.6Co0.4)(27.5)Ti-1.5. For the Ga substituted alloy with Co=0.4, a large difference of similar to 50 degrees C in T-C was noted. M-S values of 41 and 35 emu/g were observed in alloys with Co=0.4 and Ga=0.1, and Co=0.4, respectively, at room temperature. Ga substitution increased the anisotropy field value, H-A, but lowered the intrinsic coercivity value, H-ci. In the alloys with Co=0.4 and Ga=0.1, and Co=0.4, spin reorientation transitions (T-SR) were observed at 220 and 140 K respectively. The low values of H-ci observed in melt-spun ribbons are attributed to large amounts of a soft alpha-Fe phase. (c) 2007 American Institute of Physics.