Spectral fingerprinting: microstate readout via remanence ferromagnetic resonance in artificial spin ice

Abstract

Artificial spin ices are magnetic metamaterials comprising geometrically tiled strongly-interacting nanomagnets. There is significant interest in these systems spanning the fundamental physics of many-body systems and potential applications in neuromorphic computation, logic, and recently reconfigurable magnonics. Magnonics-focused studies on ASI have to date have focused on the in-field GHz spin-wave response, convoluting effects from applied field, nanofabrication imperfections ('quenched disorder') and microstate-dependent dipolar field landscapes. Here, we investigate zero-field measurements of the spin-wave response and demonstrate its ability to provide a ‘spectral fingerprint’ of the system microstate. Removing applied field allows deconvolution of distinct contributions to reversal dynamics from the spin-wave spectra, directly measuring dipolar field strength and quenched disorder as well as net magnetisation. We demonstrate the efficacy and sensitivity of this approach by measuring ASI in three microstates with identical (zero) magnetisation, indistinguishable via magnetometry. The zero-field spin-wave response provides distinct spectral fingerprints of each state, allowing rapid, scaleable microstate readout. As artificial spin systems progress toward device implementation, zero-field functionality is crucial to minimise the power consumption associated with electromagnets. Several proposed hardware neuromorphic computation schemes hinge on leveraging dynamic measurement of ASI microstates to perform computation for which spectral fingerprinting provides a potential solution.

Ultrastrong magnon-magnon coupling and chiral spin-texture control in a dipolar 3D multilayered artificial spin-vortex ice

“…To demonstrate the degree of zero-field magnon configurability, Fig. 2 e shows a ‘remanence FMR’ sweep 57 where all spectra are recorded at H ext = 0. The x -axis represents a ‘state preparation field’ H prep , which is applied momentarily prior to spectra measurement.…”

Collective Ferromagnetism of Artificial Square Spin Ice

“…While the hysteresis loops suggest that shape S2 is a more appropriate model to capture the behavior of our system, the effects of inter-island interactions indicate that a more nuanced understanding is required. [54] Figure 5 shows a mapping of the magnetization from simulations for both island shapes S1 and S2, at fields corresponding to MS, MR, HC for a = 280, 320, and 1000 nm. The arrows show the local direction of the magnetization, and the color scale indicates the local value of my for islands aligned along the x-axis.…”

Low power continuous-wave all-optical magnetic switching in ferromagnetic nanoarrays

“…Artificial spin systems comprising networks of strongly interacting nanomagnets serve as promising hosts for future information-processing technologies, including nanomagnetic logic, 27,28 neuromorphic computation, [29][30][31][32][33][34][35] and reconfigurable magnonics. [36][37][38][39][40][41][42][43] Information can be stored in the magnetization of a single nanomagnet or the magnetic configuration of the entire network (microstate), where collective microstate-dependent dynamics 36,40,44 may be harnessed to process information. [31][32][33][34][35] Local nanomagnet switching has been achieved through diffraction-limited heat-assisted reversal, relying on global fields in conjunction with laser illumination 2,45 and by cumbersome field-assisted 46 and field-free scanning-probe 41,47,48 techniques.…”