Direct and quantitative determination of the orbital ordering in by X-ray diffractionY. Tanaka1, U. Staub2, K. Katsumata1, S. W. Lovesey1, 3, J. E. Lorenzo4, Y. Narumi5, V. Scagnoli2, S. Shimomura6, Y. Tabata7, Y. Onuki7, Y. Kuramoto8, A. Kikkawa1, T. Ishikawa1 and H. Kitamura1
1 SPring-8/RIKEN - Mikazuki, Sayo, Hyogo 679-5148, Japan
2 Swiss Light Source, Paul Scherrer Institut - CH-5232 Villigen, Switzerland
3 Diamond Light Source, Rutherford Appleton Laboratory - Oxfordshire OX11 0QX, UK
4 Laboratoire de Cristallographie, CNRS - BP 166, 38042 Grenoble, France
5 KYOKUGEN, Osaka University - Toyonaka, Osaka 560-8531, Japan
6 Department of Physics, Faculty of Science and Technology, Keio University Hiyoshi, Yokohama 223-8522, Japan
7 Graduate School of Science, Osaka University - Toyanaka, Osaka 560-0043, Japan
8 Graduate School of Science, Tohoku University - Sendai 980-8578, Japan
received 19 July 2004; accepted in final form 13 October 2004
published online 5 November 2004
Results of non-resonant X-ray Bragg diffraction by are reported. This material has been described in terms of a simple antiferro-quadrupolar order below . We determine for the first time, directly and quantitatively the orbital ordering in this material. In particular, we find direct evidence for a simultaneous ordering of a quadrupole (QP) and a hexadecapole (HDP) moments below . From a strong dependence of the Bragg intensity on applied magnetic field in phase II, we conclude that octupole (OP) moments are induced and are coupled to the QP and HDP moments. When spontaneous magnetic dipole order sets in below (phase III), a large enhancement of the Bragg intensity confirms the coupling between the dipole and the QP, OP and HDP moments.
71.20.Eh - Rare earth metals and alloys.
71.27.+a - Strongly correlated electron systems; heavy fermions.
75.25.+z - Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.).
© EDP Sciences 2004