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Magnetic domain engineering in antiferromagnetic $Cu Mn As$ and $Mn$ $_{2}$ $Au$

Sonka Reimers, Olena Gomonay, Oliver J. Amin, Filip Krizek, Luke X. Barton, Yaryna Lytvynenko, Stuart F. Poole, Vit Novák, Richard P. Campion, Francesco Maccherozzi, Gerardina Carbone, Alexander Björling, Yuran Niu, Evangelos Golias, Dominik Kriegner, Jairo Sinova, Mathias Kläui, Martin Jourdan, Sarnjeet S. Dhesi, Kevin W. Edmonds, and Peter Wadley

Phys. Rev. Applied 21, 064030 – Published 12 June 2024

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Abstract

Antiferromagnetic materials hold potential for use in spintronic devices with fast operation frequencies and field robustness. Despite the rapid progress in proof-of-principle functionality in recent years, there has been a notable lack of understanding of antiferromagnetic domain formation and manipulation, which translates to either incomplete or nonscalable control of the magnetic order. Here, we demonstrate simple and functional ways of influencing the domain structure in $Cu Mn As$ and $Mn$ $_{2}$ $Au$ , two key materials of antiferromagnetic spintronics research, using device patterning and strain engineering. Comparing x-ray microscopy data from two different materials, we reveal the key parameters dictating domain formation in antiferromagnetic devices and show how the nontrivial interaction of magnetostriction, substrate clamping, and edge anisotropy leads to specific equilibrium domain configurations. More specifically, we observe that patterned edges have a significant impact on the magnetic anisotropy and domain structure over long distances and we propose a theoretical model that relates short-range edge anisotropy and long-range magnetoelastic interactions. The principles invoked are of general applicability to the domain formation and engineering in antiferromagnetic thin films at large, which will hopefully pave the way toward realizing truly functional antiferromagnetic devices.

Received 17 November 2023
Revised 19 February 2024
Accepted 17 May 2024

DOI:https://doi.org/10.1103/PhysRevApplied.21.064030

Physics Subject Headings (PhySH)

Magnetic anisotropy Magnetic domains Magnetism Magnetoelastic effect Spintronics

Antiferromagnets

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Sonka Reimers^1,2,3,*, Olena Gomonay², Oliver J. Amin¹, Filip Krizek⁴, Luke X. Barton¹, Yaryna Lytvynenko ^2,5, Stuart F. Poole¹, Vit Novák ⁴, Richard P. Campion¹, Francesco Maccherozzi³, Gerardina Carbone⁶, Alexander Björling⁶, Yuran Niu⁶, Evangelos Golias⁶, Dominik Kriegner ^4,7, Jairo Sinova², Mathias Kläui^2,8, Martin Jourdan ^2,†, Sarnjeet S. Dhesi³, Kevin W. Edmonds¹, and Peter Wadley ¹

¹School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom
²Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
³Diamond Light Source, Chilton OX11 0DE, United Kingdom
⁴Institute of Physics, Czech Academy of Sciences, 162 00 Praha 6, Czech Republic
⁵Institute of Magnetism of the National Academy of Sciences (NAS) of Ukraine and the Ministry of Education (MES) of Ukraine, 03142 Kyiv, Ukraine
⁶MAX IV Laboratory, 224 84 Lund, Sweden
⁷Institute of Solid State and Materials Physics, Technical University Dresden, 01069 Dresden, Germany
⁸Center for Quantum Spintronics, Norwegian University of Science and Technology (NTNU), 7034 Trondheim, Norway

^*Corresponding author: [email protected]
^†Corresponding author: [email protected]

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Vol. 21, Iss. 6 — June 2024

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Figure 1
The effect of patterning along a magnetic easy axis in $Cu Mn As$ . (a) AF domains in a nonpatterned area imaged by XMLD PEEM. The orange arrows show the direction and polarization of the incident x-ray beam, which yields sensitivity to the spin axis as shown by the red double-headed arrows. (b)–(d) AF-domain images in (b) 15- $μ m$ -, (c) 10- $μ m$ -, and (d) 5- $μ m$ -wide bars along an easy axis. (e) An AF-domain image of a 15- $μ m$ -wide bar with orthogonal orientation. (f) A scanning x-ray diffraction microscopy (SXDM) image of the same bar showing the microtwin configuration. (g),(h) The same as (e) and (f) but for a 10- $μ m$ -wide bar.
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Figure 2
The effect of patterning along a magnetic hard axis in $Cu Mn As$ . (a) AF domains in a square-shaped almost microtwin-free device imaged with x-ray polarization along a $Cu Mn As$ $⟨ 110 ⟩$ direction, as indicated by the double-headed orange arrows. The yellow dashed lines mark the positions of microtwin defects. (b) The same device, but imaged with x-ray polarization imaged with x-ray polarization along a $Cu Mn As$ $⟨ 100 ⟩$ direction, which reveals that the AF spin axis aligns perpendicular to the edge.
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Figure 3
The gradient anisotropy in $Cu Mn As$ bars. (a),(b) $180^{\circ}$ DWs in a $Cu Mn As$ bar. (c) The dependence of the widths of the DWs in (a) and (b) on the distance to the edge, measured with respect to the colored edge. The green and yellow data points correspond to the images in (a) and (b). The dashed line shows the simulated dependence of the DW width. The dotted line shows the DW width measured in nonpatterned areas of the sample. (d) A schematic illustrating the origin of the effect. The purple sheet displays the magnetoelastic charge density causing the destressing field $u$ shown in the inset (yellow curve). This field opposes the single-domain state and reduces the anisotropy toward the center of the bar.
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Figure 4
The effect of patterning in $Mn$ $_{2}$ $Au$ . (a) A nonpatterned area. (b),(c) In a (b) 10- $μ m$ -wide and a (c) 2- $μ m$ -wide bar along the magnetic easy axes. (d),(e) Same as (b) and (c) but for bars with orthogonal orientation. (f) AF domains in a 10- $μ m$ -wide bar along a magnetic hard axis. The orange arrows show the direction and polarization of the incident x-ray beam.
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Figure 5
Gradient anisotropy in $Mn$ $_{2}$ $Au$ bars. (a) AF domains in a 10- $μ m$ -wide $Mn$ $_{2}$ $Au$ bar. (b) The average domain population as a function of the distance to the left edge. The purple dots are experimental data and the black dashed line is a theoretical simulation. (c) The magnetoelastic charge configuration before patterning: purple and yellow correspond to opposite charge. (d) The magnetoelastic charge configuration after patterning. Edge anisotropy imposes alignment of the AF spin axis at the edges, creating an imbalance of charges. This increases the destressing energy, so that the film reacts by the expansion of domains with opposite charge in the center.
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Magnetic domain engineering in antiferromagnetic CuMnAs and Mn2Au

Phys. Rev. Applied 21, 064030 – Published 12 June 2024

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Magnetic domain engineering in antiferromagnetic $Cu Mn As$ and $Mn$ $_{2}$ $Au$