Spin Dynamics, Loop Formation and Cooperative Reversal in Artificial Quasicrystals with Tailored Exchange Coupling

TL;DR

This study investigates how exchange and dipolar interactions influence spin dynamics and magnetic reconfiguration in artificial quasicrystals, revealing unique collective phenomena and potential for reprogrammable spintronic applications.

Contribution

It clarifies the roles of short-range exchange and long-range dipolar interactions in magnetic reconfiguration of artificial quasicrystals, demonstrating aperiodicity-specific collective effects.

Findings

Exchange-coupled lattices exhibit non-stochastic switching.

Both exchange and dipolar interactions support narrow linewidth magnonic excitations.

Reconfigurable functionalities in spintronics and magnonics are achievable.

Abstract

Aperiodicity and un-conventional rotational symmetries allow quasicrystalline structures to exhibit unprecedented physical and functional properties. In magnetism, artificial ferromagnetic quasicrystals exhibited knee anomalies suggesting reprogrammable magnetic properties via nonstochastic switching. However, the decisive roles of short-range exchange and long-range dipolar interactions have not yet been clarified for optimized reconfigurable functionality. We report broadband spin-wave spectroscopy and X-ray photoemission electron microscopy on different quasicrystal lattices consisting of ferromagnetic Ni81Fe19 nanobars arranged on aperiodic Penrose and Ammann tilings with different exchange and dipolar interactions. We imaged the magnetic states of partially reversed quasicrystals and analyzed their configurations in terms of the charge model, geometrical frustration and the formation of flux-closure loops. Only the exchange-coupled lattices are found to show aperiodicity-specific collective phenomena and non-stochastic switching. Both, exchange and dipolarly coupled quasicrystals show magnonic excitations with narrow linewidths in minor loop measurements. Thereby reconfigurable functionalities in spintronics and magnonics become realistic.