Symmetry and hyperfine fields in R2Fe17−xVxCy (R=Y, Gd; x=1, 1.5, 2 and y =0,1) intermetallics

Abstract

Magnetic compounds of the type R2Fe17−xVx (R=Y, Gd and x=1, 1.5, 2) were synthesized by arc melting (with or without interstitial carbon) and studied by x-ray diffraction (XRD), Mössbauer spectroscopy, and hysteresis loop measurements. Compounds with the structure Y2Fe17−xVx (x=1, 1.5, 2) were found to be hexagonal, whereas the intermetallics containing carbon introduced by melting and those of the type Gd2Fe17−xVx (x=1, 1.5, 2) were found to be rhombohedral. For each symmetry, the lattice parameters a/c were obtained from the XRD spectra and a considerable expansion of the unit cell volume was observed in the Y2Fe17−xVxC (x=1, 1.5, 2) systems as effect of carbon additions. Room-temperature transmission Mössbauer spectra were analyzed considering the various inequivalent iron sites and yielded the average hyperfine magnetic field. This field was studied as a function of vanadium content x for all classes of compounds under investigation. The maximum hyperfine field values were obtained for the carbides. The hysteresis loops recorded at 4.2 K in an applied field of 1.5 T provided complementary information on the saturation magnetization as a function of vanadium substitution for each group of intermetallics involved.