[1] Ecole Polytech Fed Lausanne, Inst Condensed Matter Phys, CH-1015 Lausanne, Switzerland
[2] Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland
[3] Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland
[4] CNR SPIN, I-84084 Salerno, Italy
[5] Univ Salerno, Dipartimento Fis ER Caianiello, I-84084 Salerno, Italy
[6] Natl Inst Mat Sci, Tsukuba, Ibaraki 3050047, Japan
[7] Nat High Magnet Field Lab, Tallahassee, FL 32310 USA
[8] Univ Tokyo, Inst Solid State Phys, Kashiwa, Chiba 2778581, Japan
[9] Univ Geneva, Dept Quantum Matter Phys, CH-12111 Geneva, Switzerland
[10] Univ Zurich, Inst Phys, CH-8057 Zurich, Switzerland