Tailoring spin wave channels in a reconfigurable artificial spin ice

Dr Ezio Iacocca from Northumbria University, Newcastle is visiting Leeds to present some of research to the condensed matter physics research group.

Abstract: Artificial spin ices are superlattices of patterned magnetic nanostructures geometrically arranged to display frustration by design [1]. Recent studies have explored the magnetization dynamics of artificial spin ices, finding band structures [2] that suggest applications as magnonic crystals [3]. An attractive advantage of using artificial spin ices as magnonic crystals is the potential reconfigurability of its long-range magnetic state and associated band structure. While this is not trivial in most spin ice geometries, a recently investigated geometry called “charge ice” can be accurately reconfigured with relatively simple external field protocols [4]. However, this geometry possesses a strict geometrical constraint between the magnetic elements’ length and the lattice parameter. This constraint effectively decouples the magnetic elements, as shown in the simulated spectra for both a square and charge ice in Type-I and Type-II configurations with an identical lattice constant in Figure 1a. To effectively couple magnetic elements, we propose a hybrid structure where the artificial spin ice is patterned on top of a soft magnetic underlayer. Based on micromagnetic modelling, we find that this strategy allows for both dipolar and spin-wave-mediated coupling between the elements of the artificial spin ice and the soft magnetic underlayer. In this case, the richer spectra shown in Figure 1b are numerically obtained, demonstrating that the proposed system is coupled. Moreover, we find that the low-frequency edge modes in the artificial spin ice give rise to well-defined spin-wave channels in the underlayer. These results open promising pathways for the development of reconfigurable magnonic crystals.

Host: Dr Satoshi Sasaki