Stress mediated control of spin wave dynamics via magnetoelastic coupling offers a low-power, field free approach for magnonic devices. Using ${\text{mumax}}^{3}$ simulations, we compare stress induced frequency behavior in magnetostrictive nanodot and nanowire arrays driven by surface acoustic wave excitation. We find that nanodot arrays exhibit highly robust magnetization dynamics with stress insensitive frequency spectra, whereas nanowire arrays show pronounced stress induced frequency tuning, mode transitions, and nonlinear spectral features. These results establish geometry dependent design guidelines for stable magnonic oscillators and stress tunable next generation magnonic devices.

The precondition for an effective exchange-spring(ES)/exchange-coupled(EC) system, i.e., tuning of both soft and hard phases at nanometer scale to establish suitable exchange interactions, has faced significant challenges lately in material fabrication. Here, we investigate the tuneability and enhancement of in-plane (IP) & out-of-plane (OOP) coercivities (e.g., 1467 Oe in IP & 2567 Oe in OOP) as well as energy products (e.g., $8.41 ~\text{kJ} / \mathrm{m}^{3}$ in IP & $7.47 ~\text{kJ} / \mathrm{m}^{3}$ in OOP) in electrodeposited rare-earth-free CoPtP (cobalt-platinum-phosphorus) films. We observe the crossover from non-ES to ES magnetic states along OOP direction in $\text{Co}_{80}\left(\text{PtP}_{20}\right.$ films (in single material system), developed on $\text{Cu}(111) / \text{Ti}^{2} / \text{SiO}_{2}-\text{Si}$ substrates by lowering current densities from 24 to $19 ~\text{mA} / \text{cm}^{2}$ during electrodeposition from a stable CoPtP bath at room temperature. XRD patterns (at $2 \theta=43.55^{0}$) & corresponding magnetic measurements show the Co-hcp(002) phase (hard magnetic) dominates intrinsically over either Co-fcc(111) phase (soft magnetic) at $2 \theta=43.4^{0}$ or amorphous CoPtP phase (soft magnetic) with decreasing deposition current densities.

This work investigates a three-layer magnetostrictive-piezoelectric-magnetostrictive (Metglas-PZT-Metglas) laminate for magnetoelectric (ME) antenna applications. We analyze near-field behavior via coupled multiphysics simulations and far-field radiation through surface current integration. Experimental results under varied AC/DC magnetic bias show a distinct bias-dependent ME response, aligning well with the numerical models. The compact device exhibits a dipole-like radiation profile confirming its potential for efficient signal transmission and wireless communication.

This work presents a dynamical investigation of electromagnetic-based nonlinear vibrational energy harvesters, featuring distinct spring architectures to engineer unimodal/monostable nonlinear potential energies, while enhancing the performance in terms of power generation, bandwidth, and energy conversion efficiency. This has been realized by incorporating a fixed-guided design framework along with tapered-cascaded configurations. Time-resolved energy eye diagrams are used to visualize and quantify energy conversion dynamics in an excitation cycle, whereas a normalized power integral density (NPID) metric is employed to compare power and bandwidth. Experimental results supported by dynamical numerical simulations reveal that the prototype with two fixed-guided tapered springs, cascaded together, is the most effective configuration (power output: 0.29 mW at 1 g, NPID: 6.1 & times;10-3, efficiency: 33 %). Furthermore, a set of controlled electrical switching parameters have been identified from the basin of attractions enabling near-perpetual operation of the device remaining in the high-energy output branch, even when subjected to reverse frequency sweeps. This enabled successful powering of an off-the-shelf AHT20 sensor node continuously. This dynamical branch switching approach effectively overcomes the limitations associated with any multistable dissipative system, thereby leading to potentially single, steady, high-energy output state over a wide bandwidth while enabling the development of highly miniaturized autonomous power solutions, well suited for internet-of-things applications.

This paper reports electromagnetically transduced multistable non-linear vibrational energy harvesters to exploit the combined dynamical effects of monostable and bistable non-linear potential energies in a single system, by utilizing the stretching of specially designed cascaded tapered spring topology along with repulsive magnetic levitation. Using comprehensive (analytical and numerical) simulations and experimental validations, we reveal the signature of coupling and its key characteristics present in multimodal non-linear wideband energy harvesters. Here, a dynamical root-tracking technique is employed to trace stable, unstable, and hidden solution branches systematically, which enables predictive configuring of physical experimental parameters to realize previously inaccessible high response dynamical regimes along with a higher normalized power integral density metric. Thus, by tuning the powerful interplay between the numerical continuation framework and available physical parameters, we offer a robust technique for optimizing design and output performances in all such types of energy harvesting systems (independent of the scale and transduction) for their enhanced figure of merit. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license

This work reports on the design and characterization of electromagnetically transduced non-linear vibrational energy harvesters to study the interplay between non-linear potential energies, namely, monostable/quartic potential and bistable potential. We propose a dynamic root-tracking technique to reveal the signature of coupling in non-linear energy profiles. With the use of normalized power integral density (NPID) metric and energy eye-diagrams, we validate the efficacy of the system with coupled energy profile, which demonstrates maximum efficiency of 64% as compared to 46% for its monostable counterpart.

This paper reports a non-linear stretching-strain based electromagnetically transduced vibrational energy harvesters designed on low Young's modulus FR4 sheet. The reported harvesters use specially designed cascaded tapered spring topologies to tune the non-linear monostable potential energy in the system, while maintaining a consistent beam thickness of 0.25 mm. Also, a graphical representation of energy output in the form of energy eye diagrams has been introduced. These harvester units yield a maximum power of 3.2 mW with a bandwidth of 24.4 Hz when excited at an acceleration of 1g (where, g=9.8 m/s2) and have a small footprint of 0.73 cm(3) with enhanced and optimized figure of merit.

Exploring the power and phase profiles of spin waves not only enhances our fundamental understanding of magnetic materials but also opens up avenues for energy-efficient technologies such as spintronics, magnonics, and potentially reservoir computing. Here, we present the power-phase distributions and their tunability of a surface-acoustic-wave-driven "magnon microwave antenna" (MMA), comprising patterned arrays of magnetostrictive nanomagnets embedded in piezoelectric heterostructures. The MMA generates tunable microwave frequencies without external bias fields, thanks to phonon-magnon coupling, producing multimode microwave frequencies with nonvolatile spin textures. A comprehensive static magnetic study elucidates the crucial role of the demagnetization energy distribution, rather than its overall magnitude in magnetization reversal processes. Additionally, functional tunability could be achieved through amplitude-dependent training using various combinations of nanowire and nanodot dimensions, topologies, material properties, and array configurations. The nonvolatile nature of the spin textures generated in the MMA under bias-field-free conditions is promising for energy-efficient logic and low-power computing applications. Thus this work introduces a novel alternative approach, paving the way to utilize these MMAs for on-chip reservoir computing, where amplitude varies at the operating frequency.

The prerequisite of efficient exchange-spring nano-heterostructures, i.e., tuning both hard and soft phases at a nanometer level, has posed significant preparation challenges to ensure effective exchange-coupling. Here, we present a novel approach to fabricate transverse exchange-spring nano-heterostructures using single starting material through an “in situ” electrodeposition technique at room temperature. Utilizing modified acidic bath chemistry and controlled hydrogen evolution, we successfully prepared stress-free, shiny, fine-grained amorphous, and nanocrystalline Co-rich cobalt phosphorus films. These nano-heterostructured films exhibit a unique non-collinear anisotropy-driven transverse exchange-spring behavior, investigated systematically under ambient conditions. The comprehensive functional analyses reveal that intricate interplay between in-plane (IP) anisotropy of amorphous phase and out-of-plane (OOP) anisotropy generating from a nanocrystalline structure compete with each other, while producing characteristic stripe domain structures to novel corrugated stripe domain shapes. The angle-dependent first-order reversal curve distributions demonstrate new insights into the magnetic reversal mechanisms, further confirming the non-exchange-spring and exchange-spring nature of the films depending on the prevalent interfacial exchange coupling. Formation of anisotropy-driven metastable-state due to competition between IP and OOP anisotropy at a particular OOP orientation has led the normal exchange-spring structures to a transverse exchange-spring structure. Micromagnetic simulations, in excellent agreement with experimental data, further elucidate the formation of characteristic stripe domain patterns and the influence of anisotropy on the magnetic properties. The innovative methodology and detailed functional analysis presented here offer significant understanding to the field of exchange-spring magnetic materials, including anisotropy-driven metastable states, demonstrating the potential for scalable and cost-effective fabrication of advanced nano-heterostructures with tailored magnetic properties.

Abstract Exploring the power and phase profiles of spin waves not only enhances our fundamental understanding of magnetic materials but also opens up avenues for innovative applications in energy-efficient technologies such as, spintronics, magnonics, and reservoir computing. Here, we present the power-phase distributions and their tuneability of a surface acoustic wave (SAW) driven nano-patterned “Magnon Microwave Antenna” (MMA), comprised of patterned arrays of magnetostrictive nanomagnets embedded in piezoelectric heterostructures. The MMA generates tunable microwave frequencies without any external bias magnetic fields. The phonon-magnon coupling within the patterned array of nanowires and nanodots generates a multimode microwave frequencies with nonvolatile spin textures in both configurations. A comprehensive static magnetic study elucidates various magnetization reversal process within the nanowires/nanodot arrays. The investigation unveils the crucial role of the demagnetization energy distribution (strength of the dipolar magnetic field) rather than its overall magnitude. Additionally, the external bias magnetic field conditions offer the possibility of tuning the domain configuration vis-à-vis power-phase distributions of these MMAs. Notably, the non-volatile nature of the spin textures generated out of the nanowires/nanodots in the MMA, under bias-field free condition is promising for energy-efficient logic and low-power computing applications. Furthermore, given that MMA consists of piezoelectric/magnetostrictive heterostructures, this work introduces a novel alternative approach, paving the way to utilize these MMAs for on-chip reservoir computing, where amplitude varies at the operating frequency.

Spin Hall nano-oscillators (SHNOs) demonstrate self-sustained magnetization auto-oscillations, that have recently received much attention due to their potential for cutting-edge applications. In this work, the power and phase profiles, i.e., the complex quantized propagation dynamics of nano-constriction-based spin hall nano-oscillators (SHNOs) near the threshold current have been investigated. The SHNO generates a 12 GHz microwave frequency upon application of 2 mA direct current in presence of a 0.6 T external bias magnetic field. Power profile reveals that spin wave (SW) modes are quantized along x-axis. The phase profile reveals a complex nature of the SW modes at the dominant frequency (mostly localised at the nano-constriction region and additionally propagates from centre to the edges). Whereas SW mode of other frequencies mostly propagate towards the edge from the central nano-constriction region having a complex spiral nature. The SHNO devices, which are operational at high-frequencies, can be useful in energy-efficient tuneable microwave oscillators and neuromorphic computing.

Present work deals with the microstructural investigations on a variety of advanced engineering ceramics systems employing the techniques of transmission electron microscopy. In yttria stabilised zirconia alloys the tendency to acquire a duplex grain morphology during high temperature annealing could be prevented by doping with certain transition metal oxides or using Al2O3 as dispersed phase. At high temperatures the interaction of grain boundary viscous phase with the ultrafine and equiaxial grains leads to an extensive superplastic deformation in these ceramics. TEM results suggest a phenomenological model for stress accommodation, operating in three successive stages, viz. liquid phase redistribution, grain intercalation andferroelasticdomainswitchingmechanisms,respectively. Microstructural evolution in Si3N4 ceramics processed through the liquid phase sintering route shows a remarkable difference in the amount of amorphous phase content and the β–Si3N4 grain morphology depending upon the additive used. Ceramic matrix composites prepared by directed oxidation of molten Al–alloy showed a fine and isometric grain network of α–Al2O3 infiltrating the interstices of the ceramic preforms. Results on precursor effect in the phase transformation characteristics of sol–gel derived alumina ceramics are also discussed.

Here, we report a “magnon microwave antenna” (MMA) for the generation of microwaves with tuneable frequencies, based on modulation of confined spin waves (SWs) in the patterned array of magnetostrictive nanomagnets/piezoelectric heterostructures caused by the surface acoustic waves (SAWs). A SAW launched on a piezoelectric substrate produces a periodic strain within the nanomagnets patterned on it, which, in turn, stimulates magnetization precession resulting in different magneto-dynamical resonance modes in the array of nanomagnets with a rich SW texture. The generated SWs (magnons) further interact with the EM radiation (photons) at the SAW frequency. The phonon-magnon-photon coupling in the patterned array of nanowires (NWs) generates a 0.56 GHz microwave frequency with a 13.9 MHz linewidth and a ${Q}$ -factor of 40, while that in a matrix of nanodots (having same overall area) provides tuneable frequencies leading up to 30 GHz with a linewidth of 59.1 MHz and an enhanced ${Q}$ -factor of 439; having nonvolatile spin textures in both the cases. The generated nonvolatile spin textures of the NWs/nanodots can also be useful in energy-efficient logic and low-power computing applications.

From portable electronics to high-performance computing, the requirement for miniaturized and high-efficiency power supply is ever-increasing. Soft magnetic material with higher resistivity and moderate anisotropy field can be considered as a promising candidate as core materials for high-frequency integrated magnetic passives leading to such on-chip power supply devices. Here, in-plane magnetic orientation ( φ )dependent ultrafast magnetization dynamics of electrodeposited cobalt phosphorus (CoP) alloy are investigated with partial demagnetization within few hundreds of femtoseconds (fs) followed by fast and slow relaxation in relatively longer timescale. The precession frequency extracted from the magnetization precession shows dominant two-fold anisotropy superposed with a moderate four-fold anisotropy, whereas the Gilbert damping coefficient reveals a four-fold anisotropy as a function of φ . On the contrary, the ultrafast demagnetization is found to be nearly isotropic with φ . We can speculate that spin–orbit coupling (SOC) plays a major role in these anisotropic precessional dynamics but for highly non-equilibrium dynamics, the role of anisotropic SOC is negligible for ultrafast spin-flip scattering process. Such detailed studies of ultrafast spin dynamics revealing important dynamical properties will underpin potential applications in high-frequency integrated magnetic passives for future monolithic power supply on-chip.

We investigate the structural, static, and dynamic magnetic properties of exchange spring (ES) nanoheterostructured, stress-free, optically smooth films of amorphous/nanocrystalline Co-rich cobalt phosphorous (CoP) prepared by electrodeposition technique at room temperature. Static magnetic measurement reveals different hysteresis loop structures of the thin films - evolution from the low coercivity non-ES loop to the staircaseES loop, giving rise to multiple coercivities for relatively higher thickness films. The first-order reversal curve (FORC) distributions demonstrate the different reversal mechanisms present in the samples and confirm the nonES and ES natures of the films. The field-dependent Brillouin light scattering (BLS) spectra of the ES thin film unveil two well-resolved spin wave peaks associated with the bulk modes (B) and the so-called Damon-Eshbach (DE) surface spin wave modes (S) while that for non-ES low coercivity sample show a doublet of modes below a certain value of the applied field. Observation of the S mode only on one side of the measured spectra depends on the direction of the external magnetic field due to the nonreciprocal character of the S wave in the micrometer thickness of the investigated films. The external magnetic field-dependent BLS spectra yield an almost linear dependence of the mode frequencies versus the magnetic field intensity. Studied BLS measurements demonstrate the evolution of the ES structure in 5.7-& mu;m-thick nanohetero-structured CoP film compared to the 1.4-& mu;mthick non-ES sample. Additionally, the increase in the interfacial exchange energy value (JIES - 10.12 erg/cm2) in the 5.7 & mu;m film compared to that (Jnon-ES - 3.68 erg/cm2) of 1.4-& mu;m film (calculated from corresponding asymmetric peak fittings to the measured BLS spectra) reduces the interfacial exchange energy ratio (Jnon-ES below unity, confirming the enhanced strength of the exchange coupling in the developed ES film.

A wideband vibration energy harvester with multiple nonlinear forces is investigated. The nonlinearities are due to repulsive magnets and hardening springs, which gives rise to multistabilities between a number of energy branches. Not all branches are accessible by a simple up or down sweep of the driving frequency and in particular the highest energy branch is often hidden, requiring a suitable frequency schedule to be accessed. Detailed theoretical understanding of the energy branch structure along with robust experimental methods are essential for characterizing each of the energy branches to enhance the energy output from such vibration energy harvesting system. We introduce a graphical representation in the form of eye diagrams based on time-resolved measurements of acceleration and output voltage to study the dynamical features of the different branches. This generic approach allows us to optimize the design, which results in 1.3mW of power generated at 1g over 44Hz frequency bandwidth while maintaining a small footprint of $1.23 cm^3$. The energy conversion ratio of the energy harvester at 120Hz drive frequency is 0.52 for the high energy branch.

The explosive growth of wireless sensor platforms and their emerging wide range of application areas make the development of a sustainable and robust power source, an essential requirement to enable widespread deployment of these wireless devices. As a solution to this cardinal issue, this article reports the design and fabrication of a resonant vibration energy harvester (VEH) that comprises interleaved springs, manifesting a concertina-shaped structure that can enable large mechanical amplitudes of oscillation. Within a relatively small footprint (9 cm3), this concertina-VEH yields a large power density of 455.6 $\mu \text{W}$ /cm3g2 while operating at a resonant frequency of 75 Hz. Additionally, the feasibility of the implemented VEH to support near field communication (NFC)-based wireless sensor platform, that is yet uncharted, is also investigated in this work. A very low-power consumption NFC wireless sensor node has been designed and developed for this purpose. The developed concertina VEH has been employed to power the electronics interface of this NFC sensor. Using mechanical energy derived from as low as 0.2-g excitation, our study shows that the VEH can enhance the electromagnetic interaction between the transmitting antenna and the reader, resulting in a 120% increase in wireless communication range for the NFC sensor node. Such a high-performance energy harvester-assisted NFC sensor node has the potential to be used in a wide range of Internet of Things (IoT) platforms as a reliable and sustainable power solution.

Scavenging mechanical energy from ubiquitous vibrations through miniaturized electromagnetic (EM) transducers is a potential solution to the problem of powering wireless sensor networks for the Internet of Things (IoT). This letter presents the design and performance analysis of fully integrated EM vibration energy harvesters on the scale of microelectromechanical systems (MEMS). Through analytical formulation and finite element analysis, we present a systematic design study to optimize the magnet-coil interaction in a precise location within a small surface area ("footprint"). The compact device topology yielded an EM coupling as high as 62.9 mWb/m with optimized stripe-shaped micromagnets and rectangular microcoils. The nonlinear spring topology demonstrated six times improvement in the half-power bandwidth compared to its linear counterpart, at a cost of reduced power density. The designs can be implemented using standard MEMS fabrication methods leveraging CMOS-compatible integration at the system level for potential applications in the IoT.

The lack of a sustainable power source to substitute batteries for long-term applications limits the widespread deployment of wireless sensor nodes in this era of the Internet of Things. Conventional linear Vibration Energy Harvesters are inefficient in converting ambient mechanical energy into usable electrical energy owing to their narrow frequency bandwidth when harnessing mechanical energy that is spread over a wide range of frequencies. In this work, we design, develop and demonstrate high power density nonlinear wideband energy harvesters using novel tapered spring architectures in an autonomous wireless sensor node system. These spring structures exhibit a nonlinear restoring force arising from the atypical stress distribution that can be additionally tuned by changing the taper-ratio in the structure. We investigate different tapering designs in order to achieve optimal spring hardening nonlinearities. This nonlinearity aids in widening the operable bandwidth, making the harvesters suitable for scavenging energy from real-world broadband vibrations. We obtain power densities of the order of 2660 mu W/cm(3)g(2) in the nonlinear energy harvester, outpacing most contemporary energy scavengers. We present a modified Perturb and Observe algorithm that allows tracing of the maximum power point in the context of non-stationary vibration conditions. We use the fabricated nonlinear device to power a wireless sensor node that reports on vital physical parameters (humidity, temperature), thereby enabling a resilient remote data acquisition system. This demonstrates the potential of our design to provide a sustainable energy source for platforms within the Internet of Things.

The ubiquitous ambient vibrational energy is a potential candidate for solving the pertinent issue of perpetual powering of the numerous deployed wireless sensor nodes. The major roadblock in the materialization of a fully integrated high-efficiency electromagnetic vibration energy harvester is the lack of CMOS compatible magnetic materials and its integration. This work demonstrates the unique advantage of employing high performance stripe patterned array of magnets instead of conventional thin film of magnets which enhances the electromagnetic coupling factor to 53.03 mWb/m by maximizing the magnetic flux gradient within a small footprint and in a precise location. Further, it explores the benefits of employing compact in-plane moving nonlinear MEMS spring architecture, which till date is relatively unreported, that enhances the bandwidth of operation 3 times as compared with its linear counterpart at the cost of reduced peak load power. This detailed study provides a design guideline and opens up the scope for further design optimization for improving overall performance of MEMS Electromagnetic Vibration Energy Harvesters (EM-VEH).