Hyperfine interactions in RE2(Fe, Co)17 RE = Y, Gd, Dy

Mössbauer measurements are performed on RE2(Fe1−xCox)17, RE = Y, Gd, Dy compounds. The spectra are analyzed using 7 (8) subspectra for samples with Th2Zn17(Th2Ni17) structure. The differences between Fe sites, caused by the Co substitution, are neglected. A maximum value of the hyperfine field is obtained at x ≈ 0.3. This agrees with the concentration dependence of the mean 3d moment and will be discussed by means of the model of two common, partially filled 3d subbands and a model involving a portion of negative exchange. From the concentration dependence of the isomer shift charge transfers to the Fe atoms may be excluded. This is supported by the results obtained for the quadrupole splittings for 0 < x < 0.5. For 0.5 ≦ x ≦ 0.9 a rotation of the easy axis into the c-direction is obtained from the ratio of he quadrupole splitting, which agrees very well with the theoretically predicted ratio of (−1) :2.