[1] CSIC, ICMAB, Bellaterra 08193, Spain
[2] Univ Malaga, Dept Quim Inorgan Cristalog & Mineral, E-29071 Malaga, Spain
[3] Inst Max Von Laue Paul Langevin, F-38042 Grenoble, France
[4] Los Alamos Natl Lab, Condensed Matter & Thermal Phys Grp, Los Alamos, NM 87545 USA
[5] CNRS, Lab Louis Neel, F-38042 Grenoble 9, France
[6] Inst Natl Sci Appl, SNCMP, F-31077 Toulouse, France
[7] Inst Natl Sci Appl, LPMC, F-31077 Toulouse, France
[8] Katholieke Univ Leuven, LVSM, B-3001 Louvain, Belgium
[9] Univ Barcelona, Fac Quim, Dept Engn Quim & Met, E-08028 Barcelona, Spain