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

X-ray magnetic circular dichroism experiments have been performed at the R L-2,L-3 (R = rare earth) and Ni K edges on single crystals of GdNi5 and TbN i5 ferromagnetic compounds. The spectra present huge and well-structured di chroic signals at both the R L2,3 and the Ni K edges. Structures due to the quadrupolar (2p --> 4 f) transitions are clearly observed at the Tb L-2,L- 3 edges in TbNi5. For GdNi5 the dichroic signal presents a structure at 8 e V above the edge at both the Gd L-2 and L-3 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 o n the Ni K edge dichroic spectra. (C) 1999 American Institute of Physics. [ S0021-8979(99)60208-0].