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Importance of XY anisotropy in Sr2IrO4 revealed by magnetic critical scattering experiments

J. G. Vale, S. Boseggia, H. C. Walker, R. Springell, Z. Feng, E. C. Hunter, R. S. Perry, D. Prabhakaran, A. T. Boothroyd, S. P. Collins, H. M. Rønnow, and D. F. McMorrow
Phys. Rev. B 92, 020406(R) – Published 17 July 2015

Abstract

The magnetic critical scattering in Sr2IrO4 has been characterized using x-ray resonant magnetic scattering (XRMS) both below and above the three-dimensional antiferromagnetic ordering temperature TN. The order parameter critical exponent below TN is found to be β=0.195(4), in the range of the two-dimensional (2D) XYh4 universality class. Over an extended temperature range above TN, the amplitude and correlation length of the intrinsic critical fluctuations are well described by the 2D Heisenberg model with XY anisotropy. This contrasts with an earlier study of the critical scattering over a more limited range of temperature, which found agreement with the theory of the isotropic 2D Heisenberg quantum antiferromagnet, developed to describe the critical fluctuations of the conventional Mott insulator La2CuO4 and related systems. Our study therefore establishes the importance of XY anisotropy in the low-energy effective Hamiltonian of Sr2IrO4, the prototypical spin-orbit Mott insulator.

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  • Received 23 December 2014
  • Revised 22 April 2015

DOI:https://doi.org/10.1103/PhysRevB.92.020406

©2015 American Physical Society

Authors & Affiliations

J. G. Vale1,2,*, S. Boseggia1,3, H. C. Walker4,5, R. Springell6, Z. Feng1, E. C. Hunter7, R. S. Perry1, D. Prabhakaran8, A. T. Boothroyd8, S. P. Collins3, H. M. Rønnow2,9, and D. F. McMorrow1

  • 1London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
  • 2Laboratory for Quantum Magnetism, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
  • 3Diamond Light Source Limited, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
  • 4Deutsches Elektronen Synchrotron DESY, D-22607 Hamburg, Germany
  • 5ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, United Kingdom
  • 6Interface Analysis Centre, School of Physics, University of Bristol, Bristol BS2 8BS, United Kingdom
  • 7Centre for Science at Extreme Conditions, Peter Guthrie Tait Road, King's Buildings, Edinburgh, EH9 3FD, United Kingdom
  • 8Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
  • 9Neutron Science Laboratory, Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan

  • *j.vale@ucl.ac.uk

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Vol. 92, Iss. 2 — 1 July 2015

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