Structure and magnetic and magnetostrictive properties of (Tb/sub 0.7/Dy/sub 0.3/)/sub 0.7/Pr/sub 0.3/(Fe/sub 1-x/Co/sub x/)/sub 1.85/ (0/spl les//spl times//spl les/0.6)

Measurements of the structure, magnetic properties, and magnetostriction were made on arc-melted polycrystalline (Tb/sub 0.7/Dy/sub 0.3/)/sub 0.7/Pr/sub 0.3/(Fe/sub 1-x/Co/sub x/)/sub 1.85/ (0/spl les//spl times//spl les/0.6) alloys by X-ray diffraction, initial susceptibility, vibrating sample magnetometry, and standard strain gauge techniques. The measurements showed that the matrix of (Tb/sub 0.7/Dy/sub 0.3/)/sub 0.7/Pr/sub 0.3/(Fe/sub 1-x/Co/sub x/)/sub 1.85/ predominantly consists of the MgCu/sub 2/-type cubic Laves phase, with a small amount of PuNi/sub 3/-type and rare-earth rich phases. The amount of (Tb,Dy,Pr)(Fe,Co)/sub 2/ in (Tb/sub 0.7/Dy/sub 0.3/)/sub 0.7/Pr/sub 0.3/(Fe/sub 1-x/Co/sub x/)/sub 1.85/ increases with increasing Co concentration and becomes almost the only phase present when x/spl ges/0.4. The lattice parameter decreases approximately linearly with increasing x from 0.7357 nm when x=0 to 0.7300 nm when x=0.6. The Curie temperature increases with increasing x from 640 K when x=0 to 677 K when x=0.3, and then decreases to 572 K when x=0.6. The saturation magnetization M/sub s/ exhibits a minimum near x=0.3. The polycrystalline magnetostriction of (Tb/sub 0.7/Dy/sub 0.3/)/sub 0.7/Pr/sub 0.3/(Fe/sub 1-x/Co/sub x/)/sub 1.85/ decreases monotonically with increasing x. There is no evidence of an anomalously large /spl lambda//sub 100/ value as is the case for other R(Fe/sub 1-x/Co/sub x/)/sub 2/ compounds.