Influence of aluminum additions on exchange interaction and magnetostriction of Sm/sub 0.9/Pr/sub 0.1/Fe/sub 2/

Abstract

Structure, exchange interaction, magnetic properties and magnetostriction of series of cubic C15 MgCu/sub 2/-type rare-earth transition-metal (R-T) compounds of Sm/sub 0.9/Pr/sub 0.1/(Fe/sub 1-x/Al/sub x/)/sub 2/ (0/spl les/x/spl les/0.2) have been studied by X-ray diffraction, AC initial susceptibility, vibrating samples magnetometer and standard strain technology. The substitution of Al for Fe leads to an expansion of the lattice parameter /spl alpha/ by 5.1%. Curie temperature T/sub c/ is reduced continuously by replacing Fe with Al, which is ascribed to the decrease of the R-T coupling strength. The intersublattice coupling constant J/sub RT/, molecular field coefficient n/sub RT/, and exchange field B/sup ex/, are evaluated by a molecular field model. The decrease of J/sub RT/ with increasing Al content is related to the decrease of the number of (Sm,Pr)-Fe interacting pairs. Both the magnetostriction constant /spl lambda//sub 111/ and the polycrystalline saturation magnetostriction /spl lambda//sub s/ at room temperature decrease with the Al addition, which can be ascribed to the decrease of the coupling strength.