Investigating skyrmion stability and core polarity reversal in NdMn2Ge2

Sci. Rep. 15, 461 (2025) · DOI: 10.1038/s41598-024-82114-2

License: CC BY 4.0.

Abstract

We present a study on nanoscale skyrmionic spin textures in NdMn2Ge2, a rare-earth complex noncollinear ferromagnet. We confirm, using X-ray microscopy, that NdMn2Ge2 can host lattices of metastable skyrmion bubbles at room temperature in the absence of a magnetic field, after applying a suitable field cooling protocol. The skyrmion bubbles are robust against temperature changes from room temperature to 330 K. Furthermore, the skyrmion bubbles can be distorted, deformed, and recovered by varying strength and orientation of the applied magnetic field. We have used nitrogen-vacancy nanoscale magnetic imaging to estimate and map the magnetic stray fields originating from our NdMn2Ge2 lamella samples and find stray field magnitudes on the order of a few mT near the sample surface. Micromagnetic simulations show an overall agreement with the observed behaviour of the sample under different magnetic field protocols. We also find that the presence of the Dzyaloshinskii-Moriya interaction is not required to reproduce our experimental results. Its inclusion in the simulation leads to a reversal of the skyrmionic object core polarity, which is not experimentally observed. Our results further corroborate the stability and robustness of the skyrmion bubbles formed in NdMn2Ge2 and their potential for future spintronic applications.

Figures

13 panels with data across 3 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

Interactive data forthcoming. The figure is shown in the paper PDF for now. Page 2 of the PDF.

Fig. 2

• panel (a): STXM image at 300 K in one circular polarisation (641 eV): transmitted X-ray intensity, each scan line divided by its mean and then each column by its mean, against sample position $x$, $y$ ($\mu$m), 2 $\times$ 2 $\mu$m$^2$. The print labels this magnetic contrast (a.u.), $-1$ to 1. data.csv
• panel (b): STXM image at 326 K in one circular polarisation (641 eV): transmitted X-ray intensity, each scan line divided by its mean and then each column by its mean, against sample position $x$, $y$ ($\mu$m), 2 $\times$ 2 $\mu$m$^2$. The print labels this magnetic contrast (a.u.), $-1$ to 1. data.csv
• panel (c): STXM image at 327 K in one circular polarisation (641 eV): transmitted X-ray intensity, each scan line divided by its mean and then each column by its mean, against sample position $x$, $y$ ($\mu$m), 2 $\times$ 2 $\mu$m$^2$. The print labels this magnetic contrast (a.u.), $-1$ to 1. data.csv
• panel (d): STXM image at 328 K in one circular polarisation (641 eV): transmitted X-ray intensity, each scan line divided by its mean and then each column by its mean, against sample position $x$, $y$ ($\mu$m), 2 $\times$ 2 $\mu$m$^2$. The print labels this magnetic contrast (a.u.), $-1$ to 1. data.csv
• panel (e): STXM image at 329 K in one circular polarisation (641 eV): transmitted X-ray intensity, each scan line divided by its mean and then each column by its mean, against sample position $x$, $y$ ($\mu$m), 2 $\times$ 2 $\mu$m$^2$. The print labels this magnetic contrast (a.u.), $-1$ to 1. data.csv
• panel (f): STXM image at 330 K in one circular polarisation (641 eV): transmitted X-ray intensity, each scan line divided by its mean and then each column by its mean, against sample position $x$, $y$ ($\mu$m), 2 $\times$ 2 $\mu$m$^2$. The print labels this magnetic contrast (a.u.), $-1$ to 1. data.csv

Fig. 3

• panel (a): XMCD image at 0 mT: asymmetry $(I_{-} - I_{+})/(I_{-} + I_{+})$ of the two circular-polarisation STXM images, each scan line's mean subtracted, against sample position $x$, $y$ ($\mu$m), 3 $\times$ 3 $\mu$m$^2$. The print shows it as $m_z$ (a.u.), $-1$ to 1. data.csv
• panel (b): XMCD image at -140 mT: asymmetry $(I_{-} - I_{+})/(I_{-} + I_{+})$ of the two circular-polarisation STXM images, each scan line's mean subtracted, against sample position $x$, $y$ ($\mu$m), 3 $\times$ 3 $\mu$m$^2$. The print shows it as $m_z$ (a.u.), $-1$ to 1. data.csv
• panel (c): XMCD image at -70 mT: asymmetry $(I_{-} - I_{+})/(I_{-} + I_{+})$ of the two circular-polarisation STXM images, each scan line's mean subtracted, against sample position $x$, $y$ ($\mu$m), 3 $\times$ 3 $\mu$m$^2$. The print shows it as $m_z$ (a.u.), $-1$ to 1. data.csv
• panel (d): XMCD image at 70 mT: asymmetry $(I_{-} - I_{+})/(I_{-} + I_{+})$ of the two circular-polarisation STXM images, each scan line's mean subtracted, against sample position $x$, $y$ ($\mu$m), 3 $\times$ 3 $\mu$m$^2$. The print shows it as $m_z$ (a.u.), $-1$ to 1. data.csv
• panel (e): STXM image at 140 mT in one circular polarisation (the only image taken at this field): transmitted intensity, each scan line and then each column divided by its mean, against $x$, $y$ ($\mu$m), 3 $\times$ 3 $\mu$m$^2$, on a reversed grey scale. The print shows it as $m_z$ (a.u.). data.csv

Fig. 4

• panel (a): Stray field measured by NV magnetometry on the NdMn$_2$Ge$_2$ disk lamella at 300 nm lift height (mT) against position $x$, $y$ ($\mu$m): the 60 backward scan lines, each with its own mean subtracted. The black line of the print marks the cut hosted in (c). data.csv
• panel (c): Stray field strength (mT) along the line cut drawn in (a) against distance along it ($\mu$m), NV disc lamella, solid line. The print also shows the simulated stray field (red) and the reduced simulation (dashed), not hosted. data.csv

Cite

Samuel K. Treves et al. (14 authors). Investigating skyrmion stability and core polarity reversal in NdMn2Ge2. Sci. Rep. 15, 461 (2025). https://doi.org/10.1038/s41598-024-82114-2

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