Regensburg 2025 – scientific programme

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MA: Fachverband Magnetismus

MA 21: Frustrated Magnets I

MA 21.3: Talk

Wednesday, March 19, 2025, 10:00–10:15, H18

NMR Study of the S=1/2 1D Heisenberg Antiferromagnetic Chain Cu(C₆H₈N₂)ClBr — •Marlis Schuller⁵, Monika Jawale¹, Avinash Mahajan¹, Sanjay Bachhar¹, Saikat Nandi¹, Rahul Kumar², Athinarayanan Sundaresan², John Wilkinson³, Rabindranath Bag⁴, Sara Haravifard⁴, Norbert Büttgen⁵, Thomas Gimpel⁵, and István Kézsmárki⁵ — ¹Department of Physics, IIT Bombay, IN — ²CPMU, JNCASR, IN — ³ISIS Facility, STFC Rutherford Appleton Laboratory, GB — ⁴Department of Physics, Duke University, US — ⁵EPV, Institute of Physics, University of Augsburg, DE

Cu(C₆H₈N₂)ClBr is a possible candidate for realising the frustration-induced quantum spin-liquid phase, as proposed in a recent theoretical study by Uematsu et al. (JPSJ 90, 124703 (2021)) on the random-bond S=1/2 Heisenberg antiferromagnet on the zigzag chain. Based on µSR and bulk susceptibility data, it does not display any long-range order down to 88 mK. Mixing chlorine and bromine may generate randomness in the nearest-neighbour exchange necessary to satisfy the criteria from the aforementioned proposal. We investigated this compound by ¹H-NMR, and determined the spin-lattice relaxation rate 1/T₁(T) to probe low-energy excitations. Our study revealed a discontinuity in the relaxation rate at a characteristic temperature of approximately 2.5 K, where anomalies were observed in the specific heat and µSR experiments. These experimental results imply the emergence of a dimerised ground state.

Keywords: NMR; Quantum Spin Liquid; 1D Heisenberg Antiferromagnetic Chain