Hard x-ray magnetic circular dichroism in GdNi5 and TbNi5 single crystals

X-ray magnetic circular dichroism experiments have been performed at the R L2,3 (R=rare earth) and Ni K edges on single crystals of GdNi5 and TbNi5 ferromagnetic compounds. The spectra present huge and well-structured dichroic signals at both the R L2,3 and the Ni K edges. Structures due to the quadrupolar (2p→4f) transitions are clearly observed at the Tb L2,3 edges in TbNi5. For GdNi5 the dichroic signal presents a structure at 8 eV above the edge at both the Gd L2 and L3 edges. At the Ni K edge, though Ni is not magnetic in the RNi5 series, large intensities, up to 0.4%, are measured. The present results show the strong influence of the rare earth on the Ni K edge dichroic spectra.