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

Artificial spin ices (ASIs) are magnetic metamaterials comprising geometrically tiled strongly-interacting nanomagnets. There is significant interest in these systems spanning the fundamental physics of many-body systems to 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 minimize 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

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

All-optical magnetic switching promises ultrafast magnetization control without a magnetic field. Existing schemes typically require power-hungry femtosecond-pulsed lasers and complex magnetic materials. Here, we demonstrate deterministic, all-optical magnetic switching in simple ferromagnetic nanomagnets (Ni81Fe19, Ni50Fe50) with sub-diffraction limit dimensions using a focused low-power, linearly polarized continuous-wave laser. Isolated nanomagnets are switched across a range of dimensions, laser wavelengths, and powers. All square-geometry artificial spin ice vertex configurations are written at low powers (2.74 mW). Usually, switching with linearly polarized light is symmetry forbidden; here, the laser spot has a similar size to the nanomagnets, producing an absorption distribution that depends on the nanoisland-spot displacement. We attribute the deterministic switching to the transient dynamics of this asymmetric absorption. No switching is observed in Co or Ni nanostructures, suggesting the multi-species nature of NiFe plays a role. These results usher in inexpensive, low-power, optically controlled devices with impact across data storage, neuromorphic computation, and reconfigurable magnonics

Current-controlled nanomagnetic writing for reconfigurable magnonic crystals

Strongly-interacting nanomagnetic arrays are crucial across an ever-growing suite of technologies. Spanning neuromorphic computing, control over superconducting vortices and reconfigurable magnonics, the utility and appeal of these arrays lies in their vast range of distinct, stable magnetisation states. Different states exhibit different functional behaviours, making precise, reconfigurable state control an essential cornerstone of such systems. However, few existing methodologies may reverse an arbitrary array element, and even fewer may do so under electrical control, vital for device integration. We demonstrate selective, reconfigurable magnetic reversal of ferromagnetic nanoislands via current-driven motion of a transverse domain wall in an adjacent nanowire. The reversal technique operates under all-electrical control with no reliance on external magnetic fields, rendering it highly suitable for device integration across a host of magnonic, spintronic and neuromorphic logic architectures. Here, the reversal technique is leveraged to realise two fully solid-state reconfigurable magnonic crystals, offering magnonic gating, filtering, transistor-like switching and peak-shifting without reliance on global magnetic fields

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

All-optical magnetic switching promises ultrafast magnetization control without a magnetic field. Existing schemes typically require power-hungry femtosecond-pulsed lasers and complex magnetic materials. Here, we demonstrate deterministic, all-optical magnetic switching in simple ferromagnetic nanomagnets (Ni81Fe19, Ni50Fe50) with sub-diffraction limit dimensions using a focused low-power, linearly polarized continuous-wave laser. Isolated nanomagnets are switched across a range of dimensions, laser wavelengths, and powers. All square-geometry artificial spin ice vertex configurations are written at low powers (2.74 mW). Usually, switching with linearly polarized light is symmetry forbidden; here, the laser spot has a similar size to the nanomagnets, producing an absorption distribution that depends on the nanoisland-spot displacement. We attribute the deterministic switching to the transient dynamics of this asymmetric absorption. No switching is observed in Co or Ni nanostructures, suggesting the multi-species nature of NiFe plays a role. These results usher in inexpensive, low-power, optically controlled devices with impact across data storage, neuromorphic computation, and reconfigurable magnonics

Task-adaptive physical reservoir computing

Reservoir computing is a neuromorphic architecture that may offer viable solutions to the growing energy costs of machine learning. In software-based machine learning, computing performance can be readily reconfigured to suit different computational tasks by tuning hyperparameters. This critical functionality is missing in 'physical' reservoir computing schemes that exploit nonlinear and history-dependent responses of physical systems for data processing. Here we overcome this issue with a 'task-adaptive' approach to physical reservoir computing. By leveraging a thermodynamical phase space to reconfigure key reservoir properties, we optimize computational performance across a diverse task set. We use the spin-wave spectra of the chiral magnet Cu2OSeO3 that hosts skyrmion, conical and helical magnetic phases, providing on-demand access to different computational reservoir responses. The task-adaptive approach is applicable to a wide variety of physical systems, which we show in other chiral magnets via above (and near) room-temperature demonstrations in Co8.5Zn8.5Mn3 (and FeGe)

Observation and control of collective spin-wave mode-hybridisation in chevron arrays and square, staircase and brickwork artificial spin ices

Dipolar magnon-magnon coupling has long been predicted in nano-patterned artificial spin systems. However, observation of such phenomena and related collective spin-wave signatures have until recently proved elusive or limited to low-power edge-modes which are difficult to measure experimentally. Here we describe the requisite conditions for dipolar mode-hybridisation, how it may be controlled, why it was not observed earlier and how strong coupling may occur between nanomagnet bulk-modes. We experimentally investigate four nano-patterned artificial spin system geometries: `chevron' arrays, `square', `staircase' and `brickwork' artificial spin ices. We observe significant dynamic dipolar-coupling in all systems with relative coupling strengths and avoided-crossing gaps supported by micromagnetic-simulation results. We demonstrate reconfigurable mode-hybridisation regimes in each system via microstate control, and in doing so elucidate the underlying dynamics governing dynamic dipolar-coupling with implications across reconfigurable magnonics. We demonstrate that confinement of the bulk-modes via edge effects play a critical role in dipolar hybridised-modes, and treating nanoislands as a coherently precessing macro-spins or standing spin-waves are insufficient to capture experimentally-observed coupling phenomena. Finally, we present a parameter-space search detailing how coupling strength may be tuned via nanofabrication-dimensions and material properties

Reconfigurable magnonic mode-hybridisation and spectral control in a bicomponent artificial spin ice

Strongly-interacting nanomagnetic arrays are finding increasing use as model host systems for reconfigurable magnonics. The strong inter-element coupling allows for stark spectral differences across a broad microstate space due to shifts in the dipolar field landscape. While these systems have yielded impressive initial results, developing rapid, scaleable means to access abroad range of spectrally-distinct microstates is an open research problem.We present a scheme whereby square artificial spin ice is modified by widening a 'staircase' subset of bars relative to the rest of the array, allowing preparation of any ordered vertex state via simple global-field protocols. Available microstates range from the system ground-state to high-energy 'monopole' states, with rich and distinct microstate-specific magnon spectra observed. Microstate-dependent mode-hybridisation and anticrossings are observed at both remanence and in-field with dynamic coupling strength tunable via microstate-selection. Experimental coupling strengths are found up to g / 2$\pi$ = 0.15 GHz. Microstate control allows fine mode-frequency shifting, gap creation and closing, and active mode number selection

A phase II trial of TIP (paclitaxel, ifosfamide and cisplatin) given as second-line (post-BEP) salvage chemotherapy for patients with metastatic germ cell cancer: a medical research council trial

This phase II trial describes the use of TIP chemotherapy (paclitaxel, ifosfamide and cisplatin) as salvage for patients with metastatic germ cell cancer (GCC) who have failed initial BEP (bleomycin, etoposide and cisplatin) chemotherapy. Patients with first relapse following BEP for metastatic GCC, confirmed by biopsy or sequentially rising markers, received four courses of TIP (paclitaxel 175 mg m?² day 1, followed on days 1-5 by ifosfamide 1 g m?² intravenously (i.v.) and cisplatin 20 mg² i.v.) at 3-weekly intervals. The primary outcome measure was response to TIP. In all, 51 patients were registered, of whom 43 were eligible for response assessment. Eight achieved complete remission (CR) and 18 a partial remission with negative markers (PR-ve); favourable response rate (FRR=CR+PR-ve) 60%, 95% CI (44-75%); survival at 1 year was 70% (56-84%) and failure-free survival 36% (22-50%). In the group of 26 patients meeting the 'good-risk' criteria described by the Memorial Hospital, the FRR was 73% (52-88%) compared with 41% (18-67%) for the 17 'poor-risk' patients. These results are inferior to those previously reported for TIP in a single-centre study when it was given more intensively, at higher dose and with growth factor support. Nonetheless, TIP as described here can cure a substantial proportion of patients