Reconfigurable spin wave band structure of artificial square spin ice

TL;DR

This paper demonstrates that artificial square spin ices can be engineered as reconfigurable magnonic crystals with tunable spin wave band structures, promising for nanoscale spin-wave applications.

Contribution

The study introduces a semi-analytical method to analyze and show tunability of spin wave bands in square spin ices through external fields and element configurations.

Findings

Rich, tunable spin wave band structures identified.

Internal magnetization states lead to impurity-like bands.

Micromagnetic simulations validate the semi-analytical results.

Abstract

Artificial square spin ices are structures composed of magnetic elements arranged on a geometrically frustrated lattice and located on the sites of a two-dimensional square lattice, such that there are four interacting magnetic elements at each vertex. Using a semi-analytical approach, we show that square spin ices exhibit a rich spin wave band structure that is tunable both by external magnetic fields and the configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors. Full-scale micromagnetic simulations corroborate our semi-analytical approach. Our results show that artificial square spin ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.