Magnetic exchange interactions in RxFe80-xB20 amorphous alloys based on Sm and Gd

Amorphous R x Fe 80-x B 20 alloys (with R = Sm and Gd), in ribbon form, have been prepared by melt spinning and their magnetic properties have been studied (0 ≤ x ≤ 18). The mean field theory has been used to explain the temperature dependence of the magnetization. The Fe moment, the R moment, the Curie temperature and the exchange interactions between Fe-Fe and Fe-R atom pairs have been evaluated. The Sm moment at 4.2 K is found to be 0.73 μBP which is two times smaller than the theoretical value of 1.5 μBP indicating a conical spin structure. On the other hand, the Gd moment at 4.2 K is found to be 6.85 μBP which agree with the theoretical value indicating a collinear spin structure. The increase of Fe-R interaction with an increase of R content is attributed to an enhancement of the 3d-5d band hybridization.