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 T_N ∼ 1.7 K and T_L ∼ 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 T_N 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.