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Stretched exponential magnetic relaxation dynamics in artificial square ice revealed through x-ray photon correlation spectroscopy

Valerio Scagnoli1,2,*, Sandra H. Skjærvø1,2, Jamie R. Massey1,2, Oles Sendetskyi1,2, Naëmi Leo1,2,3, Claudio Mazzoli4, Laura J. Heyderman1,2, and Peter M. Derlet5,†

  • 1Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
  • 2PSI Center for Neutron and Muon Sciences, 5232 Villigen PSI, Switzerland
  • 3Department of Physics, School of Science, Loughborough University, LE11 3TU Loughborough, United Kingdom
  • 4National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA
  • 5Laboratory for Theoretical and Computational Physics, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

  • *Contact author: valerios@ethz.ch
  • †Contact author: peter.derlet@psi.ch
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Phys. Rev. B 112, 184407 – Published 4 November, 2025

DOI: https://doi.org/10.1103/jyf8-4g92

Abstract

X-ray photon correlation scattering measurements are undertaken on a thermally active artificial spin ice based on the square lattice, referred to as artificial square ice, to probe the fluctuation timescales as a function of temperature as the system passes through the paramagnetic-antiferromagnetic phase transition, which belongs to the two-dimensional Ising universality class. In the paramagnetic regime, a single exponential timescale is seen, whereas at and below the critical temperature, a stretched exponential decorrelation is observed, with the stretching exponent decreasing from unity down to below one-half as the temperature reduces. This trend is confirmed by kinetic Monte Carlo simulations of a simplified point-dipolar square ice system, and is in agreement with past theoretical work on the kinetic Ising model where stretched exponential relaxation due to equilibrium domain wall dynamics below the critical temperature was found.

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Phys. Rev. B 112, 184407– Published 4 November, 2025
  • Received 3 July 2025
  • Revised 12 September 2025
  • Accepted 10 October 2025
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