Hard X-ray MCD in GdNi5 and TbNi5 single crystals.

Abstract

X-ray magnetic circular dichroism (XMCD), being element and orbital selective, offers the opportunity to probe the R d and TM p band states by scanning through the R L and TM K-edge. As they mediate the exchange mechanisms in the R-TM intermetallics, these band states play an important role in the magnetic properties. Unfortunately, for these edges the interpretation of the dichroic signal is still matter of debate and the validity of the magneto-optical sum rules which relate the spin and orbital magnetic moments to XMCD spectra, is not yet proved. Most of the data were obtained from polycrystalline or powdered samples, where i) the single domain phase is never reached in anisotropic systems, ii) high fields are necessary to reach-the magnetic saturation in the isotropic ones. This strongly reduces the dichroic intensity and smears the small structures. The use of single crystals in the single domain phase would be very helpful to achieve a more quantitative analysis of the XMCD signal. The RNi 5 crystallize in the simple hexagonal CaCu5-type structure. The 3d shell of Ni is almost full and its contribution to magnetism is very small. The magnetic properties are driven by the indirect bilinear exchange interactions between R ions and the c r y s t a l l i n e e l ec t r i c f ie ld , r e spons ib l e for the magnetocrystalline anisotropy. They appear as well suited compounds to improve our knowledge of the XMCD at the R L2,3-edges. We present here the results of XMCD at the L2, 3edges of the rare earth and K-edge of Ni in single crystals of GdNi 5 and TbNi 5.