Observation of Coherent Spin Waves in a Three-Dimensional Artificial Spin Ice Structure

Sourav Sahoo,Arjen Van Den Berg,Andrew May,Anjan Barman,Sam Ladak,Amrit Kumar Mondal

doi:10.1021/acs.nanolett.1c00650

Sourav Sahoo, Arjen Van Den Berg + Show 4 more

Open Access

https://doi.org/10.1021/acs.nanolett.1c00650

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Abstract

Harnessing high-frequency spin dynamics in three-dimensional (3D) nanostructures may lead to paradigm-shifting, next-generation devices including high density spintronics and neuromorphic systems. Despite remarkable progress in fabrication, the measurement and interpretation of spin dynamics in complex 3D structures remain exceptionally challenging. Here, we take a first step and measure coherent spin waves within a 3D artificial spin ice (ASI) structure using Brillouin light scattering. The 3D-ASI was fabricated by using a combination of two-photon lithography and thermal evaporation. Two spin-wave modes were observed in the experiment whose frequencies showed nearly monotonic variation with the applied field strength. Numerical simulations qualitatively reproduced the observed modes. The simulated mode profiles revealed the collective nature of the modes extending throughout the complex network of nanowires while showing spatial quantization with varying mode quantization numbers. The study shows a well-defined means to explore high-frequency spin dynamics in complex 3D spintronic and magnonic structures.

Highlights

Harnessing high-frequency spin dynamics in threedimensional (3D) nanostructures may lead to paradigm-shifting, next-generation devices including high density spintronics and neuromorphic systems
During the past few years, three-dimensional (3D) nanomagnetism has emerged as a fascinating research field demonstrating novel physical phenomena such as curvatureinduced anisotropy,[16,17] frustration in 3D artificial spin ice (ASI) systems,18,19 3D magnonic crystals (MCs),[17,20] and noncollinear spin textures such as twisted skyrmions,[21] magnetic singularities, e.g., Bloch points,[22,23] hopfions,[24] and vortex domain walls.[25]
The study of spin waves (SWs) dynamics within interconnected 3D magnetic nanostructures is important to first of all build an elementary understanding of SW mode behaviors within such complex systems and subsequently to develop future devices which allow the propagation of SWs to be controlled in complex 3D circuits

Summary

To obtain deeper insight into the behavior of the observed

SW modes, we have numerically simulated the SW dynamics in the 3D-ASI system using the GPU-based MuMax[3] software.[50]. It captures mode profiles near the junction at position 1 and crescent-shaped cross-sections of two adjacent nanowires.

Corresponding Author

■ ACKNOWLEDGMENTS

■ REFERENCES