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Attaining the ground state of kagome artificial spin ice via ultrafast site-specific laser annealing

D. Pecchio, S. Sahoo*, V. Scagnoli†, and L. J. Heyderman‡

  • *Contact author: sourav.sahoo@psi.ch
  • †Contact author: valerio.scagnoli@psi.ch
  • ‡Contact author: laura.heyderman@psi.ch
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Phys. Rev. B 113, 054434 – Published 20 February, 2026

DOI: https://doi.org/10.1103/nl4z-3pn1

Abstract

Artificial spin ices (ASIs) provide a versatile platform to explore magnetic frustration and emergent phenomena. However, in kagome ASI, experimental access to the ground state remains elusive due to dynamical freezing. Here we demonstrate a deterministic and rewritable approach to attain the ground state using ultrafast, site-selective laser annealing. By engineering sublattice-dependent optical absorption through selective capping of the nanomagnets with Cr or utilizing different nanomagnet thicknesses, we achieve selective partial demagnetization and subsequent reversal of one nanomagnet sublattice under a subcoercive magnetic field, driving the system into the ground state in a single switching step. Magnetic force microscopy reveals nearly perfect long-range ordering, while heat-transfer simulations confirm the sublattice-selective excitation mechanism. This work establishes an ultrafast method to attain the kagome ASI ground state, which does not require a modification of the geometry of the ASI or the materials used for the individual nanomagnets. Beyond ground-state writing, this site-selective activation provides an important tool for controlling the magnetic states, which is important for applications such as reconfigurable magnonic crystals, neuromorphic computing and programmable nanomagnetic logic.

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Phys. Rev. B 113, 054434– Published 20 February, 2026
  • Received 2 October 2025
  • Revised 8 January 2026
  • Accepted 12 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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