Anisotropy and FOMP in (SmxPr1-x)(3)Fe27.5Ti1.5(x=0-1) and Pr-3(Fe1-yCoy)(27.5)Ti-1.5(y=0-0.4) compounds

Alloys of composition (SmxPr1-x)(3)Fe27.5Ti1.5 (x = 0-1) and Pr-3 (Fe1-y Co -y)(27.5)Ti-1.5 (y = 0-0.4) were synthesized and characterized in the tempe rature range of 10-1273 K in fields up to 5 T. The magnetization curves alo ng the hard direction clearly indicate the presence of a Type II FOMP (firs t order magnetization processes) below 200 K. The critical fields H-cr at w hich FOMP is observed, have been determined from the occurrence of a maximu m in dM/dH as a function of H. For (SmxPr1-x)(3)Fe27.5Ti1.5 compounds, H-cr is the largest (4.4 T at 5-10 K) for the x = 0 composition, and the lowest (1.4 T at 5-10 K) for the x = 0.5 composition. For the Pr-3(Fe1-yCoy)(27.5 )Ti-1.5 compounds, the H-cr are about 3.6 T at 5-10 K for y = 0 and 0.1 whe reas, H-cr is seen to decrease monotonically for higher Co contents. The FO MP exhibits a strong monotonically decreasing temperature dependence for bo th systems. The effects of the R sublattice (Sm and Pr) and the 3d sublatti ce (Fe and Co) on the anisotropy and FOMP are reported.