Anisotropy and FOMP in (Sm/sub x/Pr/sub 1-x/)/sub 3/Fe/sub 27.5/Ti/sub 1.5/ (x=0-1) and Pr/sub 3/(Fe/sub 1-y/Co/sub y/)/sub 27.5/Ti/sub 1.5/ (y=0-0.4) compounds

Alloys of composition (Sm/sub x/Pr/sub 1-x/)/sub 3/Fe/sub 27.5/Ti/sub 1.5/ (x=0-1) and Pr/sub 3/(Fe/sub 1-y/Co/sub y/)/sub 27.5/Ti/sub 1.5/ (y=0-0.4) were synthesized and characterized in the temperature range of 10-1273 K in fields up to 5 T. The magnetization curves along the hard direction clearly indicate the presence of a type II FOMP (first order magnetization processes) below 200 K. The critical fields H/sub cr/ at which FOMP is observed, have been determined from the occurrence of a maximum in dM/dH as a function of H. For (Sm/sub x/Pr/sub 1-x/)/sub 3/Fe/sub 27.5/Ti/sub 1.5/ compounds, H/sub 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/sub 3/(Fe/sub 1-y/Co/sub y/)/sub 27.5/Ti/sub 1.5/ compounds, the H/sub cr/ are about 3.6 T at 5-10 K for y=0 and 0.1 whereas, H/sub cr/ is seen to decrease monotonically for higher Co contents. The FOMP exhibits a strong monotonically decreasing temperature dependence for both systems. The effects of the R sublattice (Sm and Pr) and the 3d sublattice (Fe and Co) on the anisotropy and FOMP are reported.