Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 65: Quantum-Critical Phenomena II

TT 65.11: Talk

Wednesday, March 14, 2018, 17:45–18:00, HFT-FT 131

Critical phenomena in the honeycomb antiferromagnet BaNi₂V₂O₈ — •Ekaterina Klyushina^1,2, Bella Lake^1,2, Johannes Reuther^1,3, Nazmul Islam¹, Bastian Klemke¹, and Martin Mansson^4,5 — ¹Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany — ²Institut für Festkörperphysik Technische Universität Berlin, Germany — ³Freie Universität, Berlin, Germany — ⁴Materials Physics, KTH Royal Institute of Technology, Stockholm Kista, Sweden — ⁵Laboratory for Neutron Scattering & Imaging, Paul Scherrer Institute, Villigen, Switzerland

Here we investigate the critical phenomena in the quasi-two dimensional (2D) Heisenberg honeycomb antiferromagnet BaNi₂V₂O₈. Both the temperature regions below and above ordering temperature T_N were explored using the technique of neutron diffraction. The critical exponent of the order parameter and the thermal decay of the correlation length were measured and analysed by applying several theoretical approaches. The temperature dependence of the spontaneous magnetization is found to follow the power law predicted for a 2D XY magnetic system confirming the 2D planar character of BaNi₂V₂O₈ even below T_N. At the high temperatures, the thermal decay of the correlation length is fitted well by the 2D isotropic Heisenberg approach, however the agreement becomes worse when the temperature is close to T_N. Indeed, only the expression derived by Berezinskii, Kosterlitz and Thousless is found to be in a good agreement with the experimental data within the temperature range just above the T_N. This result suggests the presence of a free vortex phase close to T_N.