Coherent Spin Waves in Curved Ferromagnetic Nanocaps of a 3D-printed Magnonic Crystal

TL;DR

This study demonstrates the fabrication and characterization of a 3D magnonic crystal with coherent spin wave modes, revealing edge-localized modes and phase behaviors, advancing 3D nanomagnonics for ultrafast data processing.

Contribution

It introduces a scalable 3D magnonic crystal fabricated via two-photon lithography, showing coherent magnon modes and edge localization in a truly three-dimensional structure.

Findings

Coherent magnons observed at 14 and 24 GHz frequencies.

Edge modes are localized in curved nanocaps and are robust.

Unexpected phase evolution along the edges.

Abstract

Coherent magnon modes in a truly three-dimensional (3D) magnonic crystal have not yet been investigated. This scientific gap exists despite the numerous theoretical predictions about miniband formation and edge modes with topological protection. Such properties are key to advance nanomagnonics for ultrafast data processing. In this work, we use a scalable nanotechnology and integrate a 3D magnonic crystal to an on-chip microresonator. It was fabricated by two-photon lithography of a 3D woodpile structure and atomic layer deposition of 30-nm-thick nickel. Operated near 14 and 24~GHz, the microresonator output revealed numerous coherent magnons with distinct angular dependencies reflecting the underlying face-centred cubic lattice. Micromagnetic simulations show that the edge modes are localised in curved nanocaps and robust against changes in field orientation. Along an edge, they exhibit an unexpected phase evolution. Our findings advance functional microwave circuits with 3D magnonic crystals and fuel their visionary prospects of edge-dominated magnon modes.