Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 64: Frustrated Magnets - α-RuCl₃ and Cu-based Materials

TT 64.11: Vortrag

Mittwoch, 14. März 2018, 17:45–18:00, HFT-FT 101

Magnetic and magneto-elastic couplings in Cs₂CuCl_4−xBr_x with x = 0, 1, 2. — •Bernd Wolf, Satya Krishna Thallapaka, Elena Gati, Lars Postulka, Franz Ritter, Cornelius Krellner, and Michael Lang — Physics Institute Goethe University, SFB/TR 49, 60438 Frankfurt, GermanyFrankfurt,

Like for the intensively investigated quasi-2D frustrated triangular quantum antiferromagnet Cs₂CuCl₄, the newly discovered stoichiometric compounds Cs₂CuCl_4−xBr_x with x = 1, 2 exhibit a well-ordered local Cu environment due to a site-selective substitution of the halid atoms. We present χ(T, p) data from which the magnetic coupling constants are extracted based on a J₁ − J₂ model. We find that Cs₂CuCl₃Br₁ and Cs₂CuCl₂Br₂ exhibit a distinctly larger degree of geometric frustration of J₁/J₂ = 0.47 and 0.63, respectively, as compared to 0.29 for the pure Cl material. From the variation of the susceptibility under hydrostatic He-gas pressure up to 4 kbar for the different materials we extract the pressure dependence of J₁ and J₂ as well as the magneto-elastic coupling constants. Compared to other low-dimensional spin systems, the magneto-elastic couplings are at least two orders of magnitude smaller. We assign this behavior to structural peculiarities of this class of materials where structural rigid units, containing the magnetic centres, are embedded in a highly compressible matrix.