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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 Klyushina1,2, Bella Lake1,2, Johannes Reuther1,3, Nazmul Islam1, Bastian Klemke1, and Martin Mansson4,51Helmholtz-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 TN 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 TN. 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 TN. 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 TN. This result suggests the presence of a free vortex phase close to TN.

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