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TT: Fachverband Tiefe Temperaturen

TT 22: CE: Low-dimensional Systems - Materials 2

TT 22.4: Vortrag

Dienstag, 15. März 2011, 11:15–11:30, HSZ 304

Distinct magnetic regimes through site-selective atom substitution in the frustrated quantum antiferromagnet Cs₂CuCl_4−xBr_x — •Bernd Wolf¹, Pham Thang Cong¹, Mariano de Souza¹, Natalie Krüger¹, Amir Haghighirad¹, Franz Ritter¹, Wolf Assmus¹, Ingo Opahle², Kataryna Foyevtsova², Roser Valentí², Harald Jeschke², Leonore Wiehl³, and Michael Lang¹ — ¹Physikalisches Institut, Goethe Universität Frankfurt — ²Institut für theoretische Physik, Goethe Universität Frankfurt — ³Institut für Geowissenschaften, Goethe Universität Frankfurt

We report on a systematic study of the magnetic properties on single crystals of the solid solution Cs₂CuCl_4−xBr_x (0 ≤ x ≤ 4), which include the two known end-member compounds Cs₂CuCl₄ and Cs₂CuBr₄, classified as quasi-two-dimensional quantum antiferromagnets with different degrees of magnetic frustration. By comparative measurements of the magnetic susceptibility χ(T) on as many as eighteen different Br concentrations, we found that the in-plane and out-of-plane magnetic correlations do not show a smooth variation with x. Rather three distinct concentration regimes can be identified, which are separated by critical concentrations x_c1 = 1 and x_c1 = 2. This unusual magnetic behavior can be explained by considering the structural peculiarities of the materials, especially the distorted Cu-halide tetrahedra, which support a site-selective replacement of Cl⁻ by Br⁻ ions.