MAGNETIC-INTERACTIONS IN R(2)(FE1-XGAX)(17) (R=DY, Y) COMPOUNDS

By using X-ray diffraction and magnetic measurements, the structural a nd magnetic properties of R(2)(Fe(1-x)Gax)(17) (R = Dy, Y) compounds h ave been studied. It is shown that Ga substitution for Fe leads to an increase in lattice constants and a decrease in the average iron magne tic moment mu(Fe) in these compounds, while the concentration dependen ce of the Curie temperature T-C has a maximum. The exchange interactio n constants J(DyFe) and J(FeFe) in R(2)(Fe1-xGax)(17) (R = Dy, Y) comp ounds have been derived by means of mean-field analysis of T-C and the values of J(DyFe) are consistent, with those derived from a mean-fiel d analysis of the high-field magnetization. The behaviour of T-C can b e understood in terms of the concentration dependence of the exchange interaction constants.