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arXiv · 2112.00697

Low power continuous-wave all-optical magnetic switching in ferromagnetic nanoarrays

Kilian D. Stenning·Xiaofei Xiao·Holly H. Holder·Jack C. Gartside·Alex Vanstone·Oscar W. Kennedy·Rupert F. Oulton·Will R. Branford
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Abstract

All-optical magnetic switching promises ultrafast, high-resolution magnetisation control with the technological attraction of requiring no magnetic field. Existing all-optical switching schemes are driven by ultrafast transient effects, typically requiring power-hungry femtosecond-pulsed lasers and complex magnetic materials. Here, we demonstrate deterministic, all-optical magnetic switching in simple ferromagnetic nanomagnets (Ni$_{81}$Fe$_{19}$, Ni$_{50}$Fe$_{50}$) with sub-diffraction limit dimensions using a focused low-power, linearly-polarised continuous-wave laser. Isolated nanomagnets are switched across a range of dimensions, laser wavelengths and powers. All square-geometry artificial spin ice vertex configurations are written, including ground-state and energetically-unfavourable `monopole-like' states at powers as low as 2.74 mW. Usually, magnetic switching with linearly polarised light is symmetry-forbidden; however, here the laser spot has a similar size to the nanomagnets, producing an absorption distribution dependent on the relative nanoisland-spot displacement. We attribute the observed deterministic switching to the transient dynamics of this asymmetric absorption. No switching is observed in Co samples, suggesting the multi-species nature of NiFe alloys plays a role in reversal. The results presented here usher in cheap, low-power optically-controlled devices with impact across data storage, neuromorphic computation and reconfigurable magnonics.

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Kilian D. Stenning, Xiaofei Xiao, Holly H. Holder, Jack C. Gartside, Alex Vanstone, Oscar W. Kennedy, Rupert F. Oulton, Will R. Branford. 2021-12-01. Low power continuous-wave all-optical magnetic switching in ferromagnetic nanoarrays. https://arxiv.org/abs/2112.00697

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