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Effect of exchange-bond randomization in a highly two-dimensional quantum Heisenberg antiferromagnet

ORAL

Abstract

We present an investigation of the effect of randomizing exchange coupling strengths in the S = 1/2 square lattice quasi-two-dimensional quantum Heisenberg antiferromagnet (QHAF) (QuinH)2Cu(ClxBr1−x)4●2H2O (QuinH = Quinolinium, C9H8N+), with 0 ≤ x ≤ 1. Pulsed-field magnetization allows us to estimate an effective in-plane exchange strength in a regime where exchange fosters short-range order, while the temperature at which long-range order occurs (TN) is found using muon-spin relaxation, allowing us to construct a phase diagram for the series. We evaluate the effectiveness of disorder in suppressing the TN and the ordered moment size and find an extended disordered phase in the region 0.4 ≤ x ≤ 0.8 where no magnetic order occurs. The observed critical substitution levels are accounted for by an energetics-based competition between different local magnetic orders. We demonstrate experimentally that the ground-state disorder is driven by quantum effects of the exchange randomness, a feature that has been predicted theoretically and has implications for other disordered quasi-two-dimensional QHAFs.

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Presenters

  • Paul Goddard

    Department of Physics, University of Warwick, University of Warwick, Physics, University of Warwick

Authors

  • Paul Goddard

    Department of Physics, University of Warwick, University of Warwick, Physics, University of Warwick

  • Fan Xiao

    Laboratory for Neutron Scattering, Paul Scherrer Institut

  • William Blackmore

    Department of Chemistry, University of Manchester, Manchester University

  • Benjamin Michael Huddart

    Department of Physics, Durham University, Department of Physics, University of Durham

  • Matjaz Gomišek

    Jozef Stefan Institute

  • Thomas J Hicken

    Department of Physics, Durham University

  • Chris Baines

    Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Paul Scherrer Institut

  • Peter J Baker

    ISIS Pulsed Neutron and Muon Facility, STFC Rutherford Appleton Laboratory, ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX110QX, United Kingdom, ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, UK

  • Francis L Pratt

    ISIS Pulsed Neutron and Muon Facility, STFC Rutherford Appleton Laboratory

  • Stephen Blundell

    Department of Physics, University of Oxford, University of Oxford, Physics, University of Oxford, Univ of Oxford

  • Helen Lu

    National High Magnetic Field Laboratory, Los Alamos National Laboratory, National High Magnetic Field Laboratory (NHMFL), Los Alamos

  • John Singleton

    National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos National Lab, Los Alamos National Laboratory, LANL, NHMFL, National High Magnetic Field Laboratory (NHMFL), Los Alamos

  • Dariusz Gawryluk

    Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute

  • Mark Turnbull

    Carlson School of Chemistry and Biochemistry and Department of Physics, Clark University, Clark University

  • Karl W Krämer

    Department of Chemistry and Biochemistry, University of Bern

  • Tom Lancaster

    Department of Physics, Durham University, Department of Physics, University of Durham