Mutual influence between macrospin reversal order and spin-wave dynamics in isolated artificial spin-ice vertices

Abstract

We theoretically and experimentally investigate magnetization reversal and associated spin wave dynamics of isolated threefold vertices that constitute a Kagome lattice. The three permalloy macrospins making up the vertex have an elliptical cross section and a uniform thickness. We study the dc magnetization curve and the frequency vs. field curves (dispersions) of those spin wave modes that produce the largest response. We also investigate each macrospin reversal from a dynamic perspective, by performing micromagnetic simulations of the reversal processes, and revealing their relationships to the soft mode profile calculated at the equilibrium state immediately before reversal. The theoretical results are compared with the measured magnetization curves and FMR spectra. The agreement achieved suggests that a much deeper understanding of magnetization reversal and accompanying hysteresis can be achieved by combining theoretical calculations with static and dynamic magnetization experiments.

Angular-dependent spin dynamics of a triad of permalloy macrospins

“…As first found in Ref. [20], in separated macrospin vertices (i.e., interacting only magnetostatically), the modes that are likely to give a large FMR signal consist of the fundamental modes of each individual macrospin. In the present case, we might anticipate three main modes, each localized in one of the three macrospins.…”

“…The present study aims at achieving a better understanding of the basic properties of interactions within individual spin-ice building blocks [20]. In particular, it would be of considerable interest to know to what extent the spectra of complex systems might be predicted from the specific spectrum of the individual irreducible [21] building blocks, a possibility strongly supported by the results presented here.…”

Advances in artificial spin ice

“…In particular, the emergent magnetic monopoles created during magnetization reversal in an applied magnetic field (Fig. 4b) can be detected using ferro magnetic resonance (FMR) that, with its sensitivity to local magnetic fields, provides a way to distinguish contributions from different vertex types in the spectra 113,114 . The frequency spectrum for an artificial square ice in the low-field regime (Fig.…”

Tunable magnetization dynamics in artificial spin ice via shape anisotropy modification

“…This fact combined with the S mode only occurring in (g) and (h) explains the different mode numbers for each of the three cases. the experimental data which are localized at nanowire ends, so-called edge modes, with significantly lower power and are not typically seen in experiments [26,27] so are not shown in simulations for clarity. We note that there does appear to be some mode hybridization within the wide nanowire in Figs.…”

“…Recent studies have investigated individual weakly interacting vertices with asymmetric nanowire sizes [26,27]. They focus on the switching mechanisms in these systems using ferromagnetic resonance (FMR) and simulations but do not investigate the angular dependence.…”