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Phase coexistence and transitions between antiferromagnetic and ferromagnetic states in a synthetic antiferromagnet

C. E. A. Barker1,2,*, K. Fallon3, C. Barton2, E. Haltz1, T. P. Almeida3, S. Villa3, C. Kirkbride3, F. Maccherozzi4, B. Sarpi4 et al.

S. S. Dhesi4, D. McGrouther3, S. McVitie3, T. A. Moore1, O. Kazakova2, and C. H. Marrows1,†

  • 1School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
  • 2National Physical Laboratory, Hampton Road, Teddington TW11 0LW, United Kingdom
  • 3School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom
  • 4Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom

  • *christopher.barker@npl.co.uk
  • †c.h.marrows@leeds.ac.uk
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Phys. Rev. B 109, 134437 – Published 26 April, 2024

DOI: https://doi.org/10.1103/PhysRevB.109.134437

Abstract

In synthetic antiferromagnets (SAFs), antiferromagnetic (AFM) order and synthesis using conventional sputtering techniques is combined to produce systems that are advantageous for spintronics applications. Here we present the preparation and study of SAF multilayers possessing both perpendicular magnetic anisotropy and the Dzyaloshinskii-Moriya interaction. The multilayers have an antiferromagnetically aligned ground state but can be forced into a full ferromagnetic (FM) alignment by applying an out-of-plane field ∼100 mT. We study the spin textures in these multilayers in their ground state as well as around the transition point between the AFM and FM states at fields ∼ 40 mT by imaging the spin textures using complementary methods: photoemission electron, magnetic force, and Lorentz transmission electron microscopies. The transformation into a FM state by field proceeds by a nucleation and growth process, where skyrmionic nuclei form and then broaden into regions containing a ferromagnetically aligned labyrinth pattern that eventually occupies the whole film. Remarkably, this process occurs without any significant change in the net magnetic moment of the multilayer. The mix of antiferromagnetically and ferromagnetically aligned regions on the micron scale in the middle of this transition is reminiscent of a first-order phase transition that exhibits phase coexistence. These results are important for guiding the design of spintronic devices whose operation is based on spin textures in perpendicularly magnetized SAFs.

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Phys. Rev. B 109, 134437– Published 26 April, 2024
  • Received 5 February 2024
  • Revised 19 March 2024
  • Accepted 20 March 2024
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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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