•Increased amplitude of magnonic reservoir allows enhancing its calculating performances.•Changing the ring gain from negative to positive values provides higher amplitude of the reservoir response ...that increases fading memory.•Employing the metallized ferrite film improves nonlinearity of the magnonic reservoir, regardless of the trade-off with the fading memory.
A magnonic active ring oscillator based on an yttrium iron garnet (YIG) is a promising hardware platform for physical reservoir computing. It meets the required conditions for the availability of fading memory and nonlinearity. However, its performance still needs further improvement. Two methods can be employed to improve the performance. One is increasing the time of establishing steady self-oscillations in the auto-oscillator. The second one is increasing the amplitude of spin waves propagating in the YIG film. In this work, we achieve an increase of the amplitude of the reservoir response by broadening the available range for the ring gain coefficient. We use a metallized YIG film as a waveguide in which spin waves propagate. This shifts up the amplitude threshold for the development of spin wave modulation instability in the ring. The threshold defines the upper limit of the gain range for the ring. Binary pulse sequence is entered into the ring by switching its gain between upper and lower levels. The modulation instability threshold then sets the upper limit for the higher gain level. In addition, in this work, we set the lower level of the gain to negative values. This is one more improvement with respect to earlier works. Switching the gain between a negative and a positive value increases the amplitude of the reservoir response and the depth of its fading memory. We employ the standard short-term memory and parity-check tests to quantify the performance of the reservoir computer. Both tests demonstrate an increase in the computational efficiency of the magnonic reservoir.
We investigate the ferromagnetic resonance (FMR) response of thin Ni x Co y Pd 1- x-y alloy films. An FMR shift similar to Co-Pd alloy thin films is found in the presence of hydrogen gas in the ...sample environment. We find that the measured change in effective magnetization has an exponential dependence on the Pd concentration in the alloy. Additionally, we find a sudden decrease in sensitivity to hydrogen for low hydrogen concentrations.
In this work we measure hydrogen gas concentration using ferromagnetic resonance in a Pd/Co bi-layer film. The gas detection method is based on a previously demonstrated ferromagnetic resonance (FMR) ...peak shift which occurs in the presence of hydrogen. We find however that the maximum range of hydrogen concentrations which can normally be measured using this approach is smaller than the whole potential concentration range (i.e. 0%–100%); with the width of the accessible range being dictated by the width of the ferromagnetic resonance line. However, we demonstrate that this challenge can be addressed by exploiting the fact that the FMR peak position depends on the magnetic field applied to the sample. We show that by properly adjusting the magnetic field, overlapping sub-ranges covering a very wide range of hydrogen gas concentrations, from 0.2% to 100%, can been accessed. We speculate that a real-world broad-range device will be composed from 3 to 4 sensors, each of them tuned to a particular sub-range of concentrations and that shape-anisotropy bias can be used instead of applying external magnetic fields to the sensors.
•Sensitivity of ferromagnetic resonance in Pd/Co films to H2 was measured.•This was demonstrated over a large range of H2 concentrations – 0.2%–100%.•A careful choice of the magnetic bias field optimises the sensitivity.•Concentration resolution decreases when increasing the H2 concentration.•However, it remains significant when approaching 100% H2.
•Detailed numerical analysis of a magnonic reservoir computer based on a spin-wave active ring resonator is carried out.•We determined how physical parameters of the reservoir computer affect ...computational performance.•We demonstrate a potential for a significant increase in the reservoir computer efficiency.
We carry out numerical simulation of the performance of a physical reservoir computer based on a magnonic active ring oscillator. Our numerical model is based on the theory of nonlinear spin-wave transient processes in magnetic films. We employ-two metrics to evaluate the performance, namely the short-term memory and parity-check capacities. Obtained results demonstrate that there exists high potential for improvement of performance characteristics of the reservoir computer. Finally, we formulate optimal physical parameters for the magnonic reservoir. Our numerical model shows that the optimized reservoir will be able to increase its short-term memory and parity check capacities by two times with respect to the experimentally demonstrated in recent papers.
We demonstrate theoretically a large transverse magneto-optical Kerr effect (TMOKE) in subwavelength gratings consisting of alternating magneto-insulating and nonmagnetic dielectric nanostripes. The ...reflectivity of the grating reaches 96% at the frequencies corresponding to the maximum of the TMOKE response. The combination of a large TMOKE response and high reflectivity is important for applications in 3D imaging, magneto-optical data storage, and magnonics.
The influence of an electrical current on the propagation of magnetostatic surface waves is investigated in a relatively thick (40 nm) permalloy film both experimentally and theoretically. Contrary ...to previously studied thinner films where the dominating effect is the current-induced spin-wave Doppler shift, the magnetic field generated by the current (Oersted field) is found to induce a strong nonreciprocal frequency shift which overcompensates the Doppler shift. The measured current-induced frequency shift is in agreement with the developed theory. The theory relates the sign of the frequency shift to the spin-wave modal profiles. The good agreement between the experiment and the theory confirms a recent prediction of a counterintuitive mode localization for magnetostatic surface waves in the dipole-exchange regime.
•Alloy formation in ultrathin Co/Pd multilayers.•Structural CoPd alloy thin film with magnetic properties of Co/Pd multilayers.•Hydrogen induced FMR shift in Co/Pd multilayers.•A dependence of this ...shift on the nominal Pd thickness.•A dependence of the magnetic damping on nominal Pd thickness in Co/Pd multilayers.
It is known that large perpendicular magnetic anisotropy is found at interfaces of cobalt (Co) with palladium (Pd). We investigated Pd/Co/Pd30/Pd multilayer thin films with very thin Co and Pd layers with ferromagnetic resonance (FMR) spectroscopy in air and in hydrogen gas. A number of samples characterised by different Pd thicknesses were studied. A ferromagnetic resonance (FMR) peak shift similar to Co/Pd bilayer thin films was observed in the presence of hydrogen gas in the sample environment for all samples. The FMR peak shift is larger for samples with thicker Pd layers. Additionally, we found a dependence of the linewidth on the Pd layer thickness and explain this with the presence of spin pumping.
Soluble amyloid-β oligomers (Aβo) trigger Alzheimer’s disease (AD) pathophysiology and bind with high affinity to cellular prion protein (PrPC). At the postsynaptic density (PSD), extracellular Aβo ...bound to lipid-anchored PrPC activates intracellular Fyn kinase to disrupt synapses. Here, we screened transmembrane PSD proteins heterologously for the ability to couple Aβo-PrPC with Fyn. Only coexpression of the metabotropic glutamate receptor, mGluR5, allowed PrPC-bound Aβo to activate Fyn. PrPC and mGluR5 interact physically, and cytoplasmic Fyn forms a complex with mGluR5. Aβo-PrPC generates mGluR5-mediated increases of intracellular calcium in Xenopus oocytes and in neurons, and the latter is also driven by human AD brain extracts. In addition, signaling by Aβo-PrPC-mGluR5 complexes mediates eEF2 phosphorylation and dendritic spine loss. For mice expressing familial AD transgenes, mGluR5 antagonism reverses deficits in learning, memory, and synapse density. Thus, Aβo-PrPC complexes at the neuronal surface activate mGluR5 to disrupt neuronal function.
•Among transmembrane PSD proteins, only mGluR5 couples Aβo-PrPC to Fyn kinase•mGluR5 also links Aβo-PrPC to calcium signaling and protein translation control•AD brain extract-induced dysregulation of neuronal calcium requires PrPC-mGluR5•Transgenic mouse memory deficits and synapse loss are reversed by mGluR5 antagonist
Amyloid-β oligomers trigger Alzheimer’s pathophysiology by binding to PrPC and disrupting synapses. Um et al. show that the mGluR5 metabotropic glutamate receptor links Aβo-PrPC to intracellular signaling. For AD mice, mGluR5 antagonism reverses deficits in learning, memory, and synapse density.
In this paper, we carry out a detailed investigation of a recently discovered effect of the increase in the ferromagnetic resonance (FMR) amplitude for cobalt-palladium layered films in the presence ...of hydrogen gas (H 2 ). We find that this effect is not correlated with the FMR peak shift in the presence of H 2 found previously. This follows from observation of a vanishing shift but a change in the amplitude of 69.5% for a sample having a 70 nm thick cobalt layer studied in this paper. The change in amplitude is found to be mainly due to the narrowing of the FMR linewidth, which has its origin in a change in the damping parameter <inline-formula> <tex-math notation="LaTeX">\alpha </tex-math></inline-formula>. The increase in the amplitude allows us to measure H 2 concentration in nitrogen as a carrier gas in a very broad range-from 0.05% to 70% with sensitivity higher than in our previous papers.
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