INFLUENCE OF GA ON THE FE ANISOTROPY IN Y2FE17-XGAX

First-and second-order anisotropy constants, K-1 and K-2, have been de termined on aligned samples of Y2Fe17-xGax (x = 0 to 7.5) compounds by measuring magnetization and torque curves at temperatures between 4.2 and 300 K. Low-held ac susceptibility has been studied from 80 K to r oom temperatures. It has been found that a partial substitution of Ga for Fe in Y2Fe17 initially decreases the absolute value of anisotropy constants thus indicating a weakening of the easy plane character of t he Fe anisotropy. The Fe anisotropy becomes uniaxial for a Ga concentr ation slightly above 6.5 atoms fu(-1). A strengthening of the uniaxial anisotropy with further increase of Ga concentration is indicated by an increase in K-1, determined by torque measurements at room temperat ures. The results show the important changes which Fe anisotropy under goes when Fe atoms are partially substituted by Ga in R2Fe17 compounds . They can be used to separate the anisotropy contributions from the F e sublattice and the R sublattice in R2Fe17-xGax compounds with magnet ic R and thus determine the influence of Ga on the magnetic anisotropy in these materials.