High magnetic field study of the Tm2Fe17 and Tm2Fe17D3.2 compounds

A magnetization study of a Tm2Fe17 single crystal and aligned powder of the deuteride Tm2Fe17D3.2 has been carried out in steady (14 T) and pulsed (60 T and, in one case, up to 74 T) magnetic fields at temperatures between 1.5 and 300 K. Tm2Fe17 is a ferrimagnet with T-C = 295 K and a spontaneous moment of 22 mu(B)/f.u. at T = 4.2 K. Of particular interest are low-temperature magnetization curves along the sixfold crystal axis c, which is an easy direction in Tm2Fe17 and a hard direction in the deuteride. In either case the magnetization increases with magnetic field undulatorily in broad steps whose height is a multiple of the atomic moment of Tm, mu(Tm) = 7 mu(B). In Tm2Fe17, the positions of the steps yield information on the Fe-Tm molecular field, 48 T on the Tm 2d site and 60 T on the Tm 2b site, whereas the crystal field parameter A(66) is found from the widths of the steps: A(66)(b) = -35 Ka(0)(-6) and A(66)(d) = -26 Ka(0)(-6) (here a(0) is the Bohr radius). It also proves possible to estimate the other sixth-order crystal field parameter: A(60) similar to -4 Ka(0)(-6) (on average for both sites). Less information can be extracted from the powder data for the deuteride. Thus, the mean molecular field on Tm in Tm2Fe17D3.2 is found to be 49 T or 9% less than in the parent binary compound.