MAGNETOSTRICTION OF POLYCRYSTALLINE CO-PD ALLOYS

Magnetostriction of polycrystalline Co100-xPdx alloys was measured by the strain gauge method from 4 to 300 K. The saturation magnetostricti on L/L)parallel-to(S)-(DELTAL/L)perpendicular-to(S)], where (DELTAL/L) parallel-to(S) and (DELTAL/L)perpendicular-to(S) are the saturated val ues (when H(E) > 5 kG) of DELTAL/L in fields parallel and perpendicula r to sample's length (L). Lambda(s) at 4 K is found to change sign fro m positive to negative value as x is increased from below x0 = 50 at. % Pd to above. This phenomenon can be understood from the split-band t heory for Co-Pd alloy. However, since some experimental facts indicate that unquenched orbital moments may exist in the x > 50 at. % Pd allo ys it is necessary to consider lambda(s) = lambda(s)band + lambda(s)io n, where lambda(s)band is due to the split-band theory and lambda(s)io n is from the one-ion mechanism. Under this proposal, it is possible t o explain why lambda(s)(4 K) is not antisymmetric with respect to x0. Finally, two different origins of temperature dependence of lambda(s) are discussed.