Structural, magnetic and exchange interaction studies on R2Fe17-xGax (R = Tm, Er and Sm) compounds

A detailed investigation of the structure and magnetic properties of R2Fe17-xGax (R = Tm, Er and Sm and x = 0-7) was carried out by means of powder X-ray diffraction, magnetization and AC magnetic susceptibility measurements. With increasing Ga content, a structural transformation from hexagonal Th2Ni17-type structure to rhombohedral Th2Zn17-type structure is observed in compounds Er2Fe17-xGax (x = 0-7) and Tm2Fe17-xGa, (x = 0-7). The compounds Sm2Fe17-xGax (x = 0-7) crystallize in rhombohedral Th2Zn17-type structure. The Curie temperature increases in the initial Ga concentration range, reaches a maximum and then decreases at higher Ga concentration. The exchange interaction parameter J(FeFe) reaches a maximum and then decreases whereas the value of J(RFe) is almost independent of Ga concentration. X-ray diffraction measurements on magnetically aligned powder samples show a uniaxial anisotropy for compounds with at x = 2, 3 and 4 in the Sm2Fe17-xGax series whereas, it was observed for x = 7 in the Tm2Fe17-xGax compounds. (C) 2000 Elsevier Science B.V. All rights reserved.