EFFECT OF CO SUBSTITUTION FOR FE ON MAGNETIC AND MAGNETOSTRICTIVE PROPERTIES IN SM0.88DY0.12(FE1-XCOX)(2) COMPOUNDS

Measurements of x-ray diffraction, magnetization, magnetostriction, an d Mossbauer effect were made on a series of Sm0.88Dy0.12(Fe1-xCox)(2) polycrystalline samples (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0). It was found that the system has the cubic MgCu2 structure over the whole range an d the lattice constant decreases with increasing x. Initially, replace ment of Fe results in a slight increase in both the saturation magneti zation M(S) and Curie temperature T-C, while further substitution caus es a decrease in M(S) and T-C with x. Results of Mossbauer effect stud y at room temperature show that the easy axes of magnetization remain in the [111] direction for all the samples. The concentration dependen ce of the average hyperfine field, H-hf shows a similar trend as that of M(S) and T-C, exhibiting a maximum at x=0.4 due to the increase of the magnetic moment of the Fe atom caused by the adding of cobalt. The spin-orientation diagram in Sm0.88Dy0.12(Fe1-xCox)(2) was determined by measurements of Mossbauer effect and magnetization, showing that Co substitution lowers the spin-reorientation temperature. It was also f ound from x-ray measurement that the spontaneous magnetostriction lamb da(111) increased due to Co substitution, while monotonic decrease of the saturation magnetostriction lambda(s) with Co content was observed and can be attributed to the increase of lambda(100) with opposite si gn to lambda(111), which may be caused by the filling of the d band du e to Co substitution.