Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 16: CE: Quantum-Critical Phenomena 1
TT 16.4: Vortrag
Dienstag, 23. März 2010, 14:45–15:00, H19
Magnetic properties of YbCo2Si2 studied by neutron diffraction — •Nandang Mufti, Oliver Stockert, Koji Kaneko, Cornelius Krellner, and Christoph Geibel — Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany
While for most rare earth element R magnetic ordering in RT2X2 (T= transition metal and X = Si, Ge) has been thoroughly investigated, only very few results are available for Yb homologous. In this context YbCo2Si2 is very interesting because it is isoelectronic to quantum critical system YbRh2Si2. It presents a stable Yb3+ state which shows magnetic ordering at 1.7 K. We recently grew single crystals and started a extensive study of the magnetic properties of this compound. Magnetic susceptibility, specific heat, and electrical resistivity results evidenced a pronounced easy plane anisotropy and two magnetic transitions at TN ∼ 1.7 K and TL ∼ 0.9 K. Magnetization, susceptibility and magnetoresistance measurements indicate a complex B-T phase diagram with some anisotropy in the basal plane. Here, we will present the results of our investigation with single crystal and powder neutron diffractions in absence and under magnetic field up to 2.5 T. A commensurate magnetic structure with q = (0.25, 0.25, 1) and incommensurate magnetic structure with q= (0.25, 0.08, 1) are observed for the ground state and intermediate phase, respectively. The critical exponent β for TN is obtained as β = 0.369 ± 0.03 which is close to the expected value of 3D Heisenberg system. We shall propose a magnetic structure for both ordered phases.