Switching the spin cycloid in BiFeO3 with an electric field

Nat. Commun. 15, 2903 (2024) · DOI: 10.1038/s41467-024-47232-5

License: CC BY 4.0.

Abstract

Bismuth ferrite (BiFeO3) is a multiferroic material that exhibits both ferroelectricity and canted antiferromagnetism at room temperature, making it a unique candidate in the development of electric-field controllable magnetic devices. The magnetic moments in BiFeO3 are arranged into a spin cycloid, resulting in unique magnetic properties which are tied to the ferroelectric order. Previous understanding of this coupling has relied on average, mesoscale measurements. Using nitrogen vacancy-based diamond magnetometry, we observe the magnetic spin cycloid structure of BiFeO3 in real space. This structure is magnetoelectrically coupled through symmetry to the ferroelectric polarization and this relationship is maintained through electric field switching. Through a combination of in-plane and out-of-plane electrical switching, coupled with ab initio studies, we have discovered that the epitaxy from the substrate imposes a magnetoelastic anisotropy on the spin cycloid, which establishes preferred cycloid propagation directions. The energy landscape of the cycloid is shaped by both the ferroelectric degree of freedom and strain-induced anisotropy, restricting the spin spiral propagation vector to changes to specific switching events.

Figures

7 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

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 2

• panel (a): Piezoresponse force microscopy amplitude (pm) of the BiFeO$_3$ film against position $x$, $y$ ($\mu$m). The print draws no colour scale, shows the scan without its right-hand edge (the hosted range; the full 4 $\mu$m scan is in the data) and overlays the NV map hosted as a-inset. data.csv
• panel (a-inset): NV microscopy map of the same area, dual iso-B fluorescence difference (kc/s), against scan position $X$, $Y$ ($\mu$m), the 2 $\mu$m square overlaid on (a). The print draws it without a colour scale, turned by about 90$^\circ$ against these scan axes and laid over the PFM image. data.csv

Fig. 3

• panel (b): Relative energy ($\mu$eV f.u.$^{-1}$) against the angle $\phi$ of $\mathbf{L}$ in the unstrained cell, with $\mathbf{L}$ rotated in (111) (yellow) and in $(11\bar{2})$ (red, green, blue; the print draws these three slightly apart in $\phi$). Markers are the calculated energies joined by lines; the shading fills under the red curve and the dotted line marks $\phi = 0$. data.csv
• panel (c): Relative energy ($\mu$eV f.u.$^{-1}$) against $\phi$ with the cell strained to DSO, for $\mathbf{k} \parallel [\bar{1}10]$ (red, solid line, shaded), $[\bar{1}01]$ (green) and $[0\bar{1}1]$ (blue, dotted lines). Markers are the calculated energies. The print gives no y tick labels; the hosted y axis is that of (b), whose frame and ticks it shares. data.csv

Fig. 4

• panel (b): Net polarization $P_{\mathrm{net}}$ (a.u.) against applied voltage $V$ (V) for the device of (a), a ferroelectric hysteresis loop: markers joined by a line in the order printed. data.csv
• panel (c-inset): NV microscopy map, dual iso-B fluorescence difference (kc/s), against scan position $X$, $Y$ ($\mu$m), for the device poled with net polarization to the left. The print draws no colour scale and lays the map, turned by 45$^\circ$ and cut to the device region, over the PFM image with the domain walls as black lines. data.csv
• panel (d-inset): NV microscopy map, dual iso-B fluorescence difference (kc/s), against scan position $X$, $Y$ ($\mu$m), for the device poled with net polarization to the right. The print draws no colour scale and lays the map, turned by 45$^\circ$ and cut to the device region, over the PFM image with the domain walls as black lines. data.csv

Fig. 5

The underlying data is not available. The figure is shown in the paper PDF.

Cite

Peter Meisenheimer et al. (13 authors). Switching the spin cycloid in BiFeO3 with an electric field. Nat. Commun. 15, 2903 (2024). https://doi.org/10.1038/s41467-024-47232-5

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