Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.73: Poster

Mittwoch, 24. März 2010, 14:00–18:00, Poster D1

Magnetic properties of the new low-dimensional spin magnet α-Cu₂As₂O₇ — •Yulieth Arango¹, Evgenia Vavilova², Olga Volkova³, Mahmoud Abdel-Hafez¹, Matthias Weil⁴, Alexander Vasiliev³, Vladislav Kataev¹, Rüdiger Klingeler¹, and Bernd Büchner¹ — ¹Leibniz-Institut für Festkörper und Werkstoffforschung IFW Dresden, Dresden, Germany — ²Zavoisky Physical-Technical Institute of RAS, Kazan, Russia — ³Physics Faculty, Moscow State University, Moscow, Russia — ⁴Institute for Chemical Technology and Analytics, Vienna University of Technology, Vienna, Austria

The crystal structure of α-Cu₂As₂O₇ consists of two-dimensional infinite sheets (ab-plane) of [CuO₅] polyhedra stacked along the c-axis. The Cu²⁺ (3d⁵, S=1/2) ions are connected via oxygen ligands in the Cu-O chains along the diagonal of the ab-plane. In this work we study the interplay between the crystal structure and magnetism of α-Cu₂As₂O₇ single crystals by measuring magnetic susceptibility, specific heat, high field electron spin resonance (HF-ESR), and nuclear magnetic resonance (NMR). The data reveal that in the spin sector Cu-O chains represent a realization of a quasi-one dimensional (1D) spin-1/2 anisotropic Heisenberg antiferromagnet with the nearest neighbor exchange constant J ∼ 160 K. Due to residual 3D interactions α-Cu₂As₂O₇ orders antiferromagnetically at T_N ≃ 11 K. Below T_N two phases are identified: a collinear phase and a field B induced spin-flop phase at B > B_C ≃ 1.8 T.