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In this paper, a green solvent for chitosan, plasma acid, was made and chitosan/plasma-acid solutions were prepared. An environmentally friendly chitosan/polyvinyl alcohol (PVA) nano-membrane was p...

The emerging two-dimensional ferromagnetic materials present atomic layer thickness and a perfect interface feature, which have become an attractive research direction in the field of spintronics f...

Perovskite-type lanthanide oxide is a new kind of promising electrode material for supercapacitor. In this study, La1-xSrxMn0.9Ni0.1O3 nanofibers with different Sr substitutions are prepared by electrospun method and used as electrode material firstly. The effect of Sr substitution on the structure of LaMn0.9Ni0.1O3 perovskite has been investigated, and the electrochemical properties have been tailored correspondingly. Minor Sr substitution introduces some oxygen vacancies into the perovskite structure, and optimizes the specific capacitance. However, excessive Sr substitution causes lattice distortion of the perovskite structure and deteriorates the electrochemical performance instead. The highest specific capacitance of 113.9 F·g−1 is obtained in La0.85Sr0.15Mn0.9Ni0.1O3 component.

The NiMoO4/CoMoO4 nanorod arrays wrapped by Ni-Co-S nanosheets were successfully grown on the surface of carbon cloth (NCMOS@CC) by combining of hydrothermal and electrochemical deposition methods. And the as-prepared NCMOS@CC showed good flexibility. The obtained NCMOS@CC as electrode materials were tested in a three-electrode system, showing a pretty good specific capacitance of 778.1 F g−1 at a current density of 0.5 A g−1 and excellent rate capability using 1 M KOH as the electrolyte. The flexible asymmetric supercapacitors (FASCs) were further fabricated using NCMOS@CC as the positive electrode and activated carbon@carbon cloth (AC@CC) as the negative electrode. The fabricated FASCs exhibited a safe working range with a potential window of 0–1.6 V with a maximum energy density of 33.1 Wh Kg−1 at 0.25 A g−1 and maximum power density of 3195 W kg−1 at 4 A g−1. The fabricated FASCs even bent at different angles still showed good flexibility and stable electrochemical properties. These performances enable the NCMOS@CC to be one of the potential flexible electrodes for using in flexible energy storage devices.

In this paper, a parametric level-set-based topology optimization framework is proposed to concurrently optimize the structural topology at the macroscale and the effective infill properties at the micro/meso scale. The concurrent optimization is achieved by a computational framework combining a new parametric level set approach with mathematical programming. Within the proposed framework, both the structural boundary evolution and the effective infill property optimization can be driven by mathematical programming, which is more advantageous compared with the conventional partial differential equation-driven level set approach. Moreover, the proposed approach will be more efficient in handling nonlinear problems with multiple constraints. Instead of using radial basis functions (RBF), in this paper, we propose to construct a new type of cardinal basis functions (CBF) for the level set function parameterization. The proposed CBF parameterization ensures an explicit impose of the lower and upper bounds of the design variables. This overcomes the intrinsic disadvantage of the conventional RBF-based parametric level set method, where the lower and upper bounds of the design variables oftentimes have to be set by trial and error. A variational distance regularization method is utilized in this research to regularize the level set function to be a desired distanceregularized shape. With the distance information embedded in the level set model, the wrapping boundary layer and the interior infill region can be naturally defined. The isotropic infill achieved via the mesoscale topology optimization is conformally fit into the wrapping boundary layer using the shape-preserving conformal mapping method, which leads to a hierarchical physical structure with optimized overall topology and effective infill properties. The proposed method is expected to provide a timely solution to the increasing demand for multiscale and multifunctional structure design.

Magnetic skyrmion (Sk), instead of magnetic domain wall (DW), holds great promise as alternative information carriers in the future ultradense and low-power racetrack memory (RM). More importantly, by exploiting its unique properties, such as particle-like behavior and topological stability, Sk enables new functionalities that may be inaccessible to DW in RM applications. In this paper, we propose a complementary Sk-RM structure that enables voltage-controlled local data update functionality. Similar to our previous design in addressing the data representation issue, data information is represented in a robust way that both “0” and “1” are represented in the form of Sks and are moved synchronously by the spin Hall effect. Furthermore, this complementary Sk-RM structure can be developed for enabling local data update functionality, because Sks can be shifted between the two nanotracks by regulating the voltage-controlled gates. In this case, data bits “0” and “1” can be converted to each other freely within the nanotrack without being moved out of the nanotrack. This functionality brings great benefits in data access and management. Functionality and performance of the proposed design are studied with micromagnetic simulations.

Current-induced effective magnetic fields provide efficient methods to electrically control the magnetization switching in ultrathin magnetic films. It is getting clearer that the two terms of spin-orbit torque (SOT), i.e., the dampinglike SOT and the fieldlike SOT, play different roles during the magnetization switching process. Fast and direct estimation of both effective fields are crucial for highly efficient magnetization switching. Methods to extract the amplitudes of the effective fields have been intensively investigated, but they are either complex or require multiparameter fitting, especially for the fieldlike field. We introduce the direct detection of SOT effective fields using hysteresis-loop shift through the magneto-optical Kerr effect in the out-of-plane Pt/Co/W and in-plane Pt/Fe/MgO trilayer systems. The results show strong agreement with transport measurements. Benefiting from noncontact optical detection, our approach in the detection of the spin-orbit effective field has great advantages in the simplified device fabrication processing, and it is suitable not only for metallic systems but also for insulating systems, which paves the way to direct detection of SOT effective fields.

International audience; Optical methods for magnetism manipulation have been considered as a promising strategy for ultralow-power and ultrahigh-speed data storage and processing, which have become an emerging field of spintronics. However, a widely applicable and efficient method has rarely been demonstrated. Here, the strongly correlated electron material vanadium dioxide (VO 2) is used to realize the optically induced phase change for control of the magnetism in NiFe. The NiFe/VO 2 bilayer heterostructure features appreciable modulations of electrical conductivity (32%), coercivity (37.5%), and magnetic anisotropy (25%). Further analyses indicate that interfacial strain coupling plays a crucial role in the magnetic modulation. Utilizing this heterostructure, which can respond to both optical and magnetic stimuli, a phase change controlled anisotropic mag-netoresistance (AMR) device is fabricated, and reconfigurable Boolean logics are implemented. As a demonstration of phase change spintronics, this work may pave the way for next-generation opto-electronics in the post-Moore era.

Magnetic skyrmions are promising candidates for future storage devices with a large data density. A great variety of materials have been found that host skyrmions up to the room-temperature regime. Lorentz microscopy, usually performed in a transmission electron microscope (TEM), is one of the most important tools for characterizing skyrmion samples in real space. Using numerical calculations, this work relates the phase contrast in a TEM to the actual magnetization profile of an isolated Neel or Bloch skyrmion, the two most common skyrmion types. Within the framework of the used skyrmion model, the results are independent of skyrmion size and wall width and scale with sample thickness for purely magnetic specimens. Simple rules are provided to extract the actual skyrmion configuration of pure Bloch or Neel skyrmions without the need of simulations. Furthermore, first differential phase contrast (DPC) measurements on Neel skyrmions that meet experimental expectations are presented and showcase the described principles. The work is relevant for material sciences where it enables the engineering of skyrmion profiles via convenient characterization., Comment: 6 pages, 3 figures

In spintronics, ferrimagnets continue to draw intense attention for their ultrafast dynamics, but their reduced magnetization near the compensation point plus small spin-mixing conductance do not help the spin-orbit torque in ferrimagnet/heavy-metal multilayers. This study uses two heavy metals with opposite spin Hall angles flanking a typical ferrimagnetic alloy to achieve effective enhancement of the spin Hall angle, as well as stable, controllable multilevel current-induced switching based on the proposed heterostructure. This work, combining efficient and multibit magnetization switching, provides an alternate route to leveraging ferrimagnets in spintronic devices.

The control of magnetic skyrmion creation and pinning through strain is studied by micromagnetic simulations. A single stable skyrmion can be created by a vertical strain pulse on Pd/Fe/Ir hybrid structure on Pb(Zr 1−x Ti x )O 3 nanowire with −1.8 V pulse voltage from 1.2 ns to 2.0 ns. Then the skyrmion is pinned by the vertical strain independent of the polarity during its propagation in the wire driven by the current. The proposed device integrates strain-controlled skyrmion creation and pinning in a single nanowire structure, which would open a new route for skyrmion-based memory and logic devices with ultra-low power consumption.

Methyammonium lead tri-halide perovskites (MAPbX3) are highly promising for energy conversion and photonic devices. Here, we present a comprehensive investigation into the temperature (T)-dependent carrier transport, phase transition and photoluminescence properties in single crystals of MAPbI3 (MSC, X = I), with an aim to attain an understanding of the mechanisms governing the carrier motion and phase transition in halide perovskites. We identify a tetragonal to orthorhombic phase at around 150 K. Thermal evolution of the photoluminescent (PL) peak broadening with temperature points to a dominant longitudinal-optical (LO) phonon interaction in MSCs within a wide T-range across two phase transition points. In the tetragonal phase, the hole and electron mobilities in MSC along the direction normal to the main (110) crystallographic plane exhibit an opposite T-coefficient with the one for the holes exhibiting the ∼T−1.6 dependence and that for electrons roughly following the impurity scattering at ∼T1.8. Such distinct behaviours may be understood by the electron traps due to the specific surface conditions in solution-grown MSCs, which tend to play an increasing role at lower T. Thus, seeking viable passivation approaches is critical for the realistic applications of MSCs. These findings enrich the fundamental insight into some key photophysical properties in halide perovskites and can act as a guide for advancing the application of perovskite single crystals targeted at device operation within a wide T-window.

The perovskite-type SrMn0.875Nb0.125O3 (SMN) and SrCo0.875Nb0.125O3 (SCN) materials are prepared through the solid-state reaction method as novel oxygen-intercalated electrode materials for supercapacitor. The crystal structure, powder morphology, and electrochemical performance have been characterized in detail. SMN exhibits a six-layer hexagonal (6H) structure with space group P63/mmc, while SCN shows the tetragonal structure of space group P4/mmm. Under the three-electrode system with 1 M Na2SO4 neutral electrolyte solution, the specific capacitance (Cs) of SCN can reach 894 mF cm−2 at 1 mA cm−2, which is 4.7 times the value of SMN at the same condition. For SCN, the superiority of electrochemical performance is attributed to its porous surface morphology, perovskite structure with shorter B O bond length and large B-O-B bond angle, and a higher oxygen vacancy content. When combined with activated carbon (AC) electrode, the SCN//AC asymmetric supercapacitor with a working voltage of 2.0 V presents a specific energy density of 82.33 μWh cm−2, while maintaining prominent cycling stability with a capacity retention of 88.88% after 10,000 cycles.

Several errors are present in the text and Fig. 3 of the article Ultramicroscopy 212 (2020) 112973. This includes minor confusions concerning the skyrmion helicities and a wrong orientation of a color wheel that represents the electron phase gradient direction. Further, the presented correction factors for finite probe sizes were based on an erratic simulation which is now corrected. This leads to different error values for the measured skyrmion size. These flaws do not affect the main message of the paper which is the relation of the skyrmion structure with the electron phase at all. They only affect the small section of the proof of principle skyrmion size measurement where aberrations were included.

Magnetic skyrmions are topological quasiparticles with great potential for applications in future information storage and processing devices because of their nanoscale size, high stability, and large velocity. Recently, the high-frequency properties of skyrmions have been explored for magnon nanodevices. Here we systematically study the dynamics of an isolated skyrmion under voltage excitation through the voltage-controlled magnetic anisotropy effect in a circular thin film. A theoretical model considering the demagnetization energy, which has often been neglected or treated superficially in previous skyrmion research but is demonstrated to have importance in determining the skyrmion dynamic state, is developed. With our model, the periodic oscillation of the skyrmion radius can be solved numerically with similar precision compared to micromgnetic simulations, and the characteristic frequency of the skyrmion breathing can be determined analytically with greater precision than previous studies. Furthermore, we find that the breathing skyrmion can be analogized as a modulator by investigating its linear modulation functionality under sinusoidal-form voltage excitation. Different from the conventional modulation system with complex CMOS circuits, this skyrmion modulator device integrates with both the modulation and carrier wave generation functionality, thus showing greater convenience and efficiency in applications. Our findings can provide useful guidance for both theoretical and experimental skyrmions research as well as the development of skyrmion-based magnonic devices with significant potential applicability in future communication system., 29 pages, 8 figures

Magnetic skyrmions have significant potential for applications in storage and logic devices, but the ability to control skyrmion motion is key to their success. To realize controlled skyrmion motion, vertical spin current-driven methods employing, e.g., the spin Hall or inverse spin galvanic effect, are efficient; thus, magnetic heterostructures featuring large spin-orbit torques are appealing. In this paper, we report on the observation of room-temperature magnetic skyrmions in Pt/Co/W multilayers. The interfacial Dzyaloshinskii-Moriya interaction was estimated to be $0.19\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/{\mathrm{m}}^{2}$ based on the asymmetric domain-wall motion occurring upon the application of in-plane magnetic fields. The evolution of the magnetic structures from labyrinth domains to skyrmions with diameters of around 145 nm under magnetic fields was observed by performing Lorentz transmission electron microscopy. The skyrmion nucleation fields could be tuned by varying the repetition number. Large spin Hall angle systems such as Pt/Co/W multilayers are appealing for achieving current-driven skyrmion motion in future racetrack and logic applications.

C29H16F6N2S2, monoclinic, C2/c, a = 18.910(3) Å, b = 8.5720(14) Å, c = 16.757(3) Å, β = 100.474(2)°, V = 2670.9(7) Å3, Z = 4, R gt(F) = 0.0825 , wR ref(F 2) = 0.1833 , T = 296(2) K.

Plant-based porous carbon materials are considered as one of the most promising electrode materials for manufacturing supercapacitors (SCs) due to their low-cost and natural abundance. In this work, the N-doped biomass-porous carbons with the ultra-high specific surface area were prepared from food waste soybean dregs via a very simple carbonization method. Field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) displayed the as-prepared samples with a large number of micro- and nanostructures. By optimizing the additive amount of urea and carbonization temperature, the as-prepared carbon material showed a high specific surface area up to 2004.21 m2 g−1. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests had been used to investigate the electrochemical performance of samples. The as-obtained samples exhibited a reasonable specific capacitance of 175.8 F•g−1 at 0.5 A•g−1 and good capacitance retention of 84.1% from 0.5 to 4 A•g−1.

The effect of A-site substitution by Ca or Sr on the crystal structure and electrochemical performance of LaMnO3 (LMO) perovskite have been investigated. La0.85Ca0.15MnO3 (LCM) keeps the same orthorhombic structure with the parent LMO composition, while La0·85Sr0·15MnO3 (LSM) transforms to rhombohedral structure. The A-site substituted compositions with more oxygen vacancies are more beneficial to the oxygen intercalation than the parent LMO sample according to the modified anion-intercalation mechanism, and the electrochemical performance is significantly optimized. LCM and LSM electrodes exhibit a specific capacitance of 140.5 mF cm−2 and 129.0 mF cm−2 at 0.5 mA cm−2 in an aqueous electrolyte, respectively, which are four times larger than that of LMO. LCM electrode yields the highest capacitance behavior because of the finer morphology, lower ion diffusion resistance, higher concentration of oxygen vacancy and fuller utilization of the perovskite bulk structure. In addition, LCM//LCM symmetric supercapacitor exhibits an energy density of 29.7 μWh.cm−2 at a powder density of 500 μW cm−2. Our work indicates that A-site substituted compositions by Ca or Sr exhibit great potential in the supercapacitor applications, and further optimization is expected.

In this work, we demonstrate that skyrmions can be nucleated in the free layer of a magnetic tunnel junction (MTJ) with Dzyaloshinskii-Moriya interactions (DMI) by a spin-polarized current with the assistance of stray fields from the pinned layer. The size, stability and number of created skyrmions can be tuned by either the DMI strength or the stray field distribution. The interaction between the stray field and the DMI effective field is discussed. A device with multi-level tunneling magnetoresistance is proposed, which could pave the ways for skyrmion-MTJ-based multi-bit storage and artificial neural network computation. Our results may facilitate the efficient nucleation and electrical detection of skyrmions., Comment: 4 figure in main text,14 figure in the supplementary information

Neuromorphic computing, which relies on a combination of a large number of neurons massively interconnected by an even larger number of synapses, has been actively studied for its characteristics such as energy efficiency, intelligence, and adaptability. To date, while the development of artificial synapses has shown great progress with the introduction of emerging nanoelectronic devices, e.g., memristive devices, the implementation of artificial neurons, however, depends mostly on semiconductor-based circuits via integrating many transistors, sacrificing energy efficiency and integration density. Here, we present a novel compact neuron device that exploits the current-driven magnetic skyrmion dynamics in a wedge-shaped nanotrack. Under the coaction of the exciting current pulse and the repulsive force exerted by the nanotrack edges, the dynamic behavior of the proposed skyrmionic artificial neuron device is in analogy to the leaky–integrate–fire (LIF) spiking function of a biological neuron. The tunable temporary location of the skyrmion in our artificial neuron behaves like the analog membrane potential of a biological neuron. The neuronal dynamics and the related physical interpretations of the proposed skyrmionic neuron device are carefully investigated via micromagnetic and theoretical methods. Such a compact artificial neuron enables energy-efficient and high-density implementation of neuromorphic computing hardware.

Magnetic skyrmions are promising information carriers for building future high-density and high-speed spintronic devices. However, to achieve a current-driven high-speed skyrmion motion, the required driving current density is usually very large, which could be energy inefficient and even destroy the device due to Joule heating. Here, we propose a voltage-driven skyrmion motion approach in a skyrmion shift device made of magnetic nanowires. The high-speed skyrmion motion is realized by utilizing the voltage shift, and the average skyrmion velocity reaches up to 259 m/s under 0.45 V applied voltage. In comparison with the widely studied vertical current-driven model, the energy dissipation is three orders of magnitude lower in our voltage-driven model, for the same speed motion of skyrmions. Our approach uncovers valuable opportunities for building skyrmion racetrack memories and logic devices with both ultra-low power consumption and ultra-high processing speed, which are appealing features for future spintronic applications.

Recent years have witnessed a rapidly growing interest in exploring the use of spin waves for information transmission and computation toward establishing a spin-wave-based technology that is not only significantly more energy efficient than the CMOS technology, but may also cause a major departure from the von-Neumann architecture by enabling memory-in-logic and logic-in-memory architectures. A major bottleneck of advancing this technology is the excitation of spin waves with short wavelengths, which is a must because the wavelength dictates device scalability. Here, we report the discovery of an approach for the excitation of nm-wavelength spin waves. The demonstration uses ferromagnetic nanowires grown on a 20-nm-thick Y3Fe5O12 film strip. The propagation of spin waves with a wavelength down to 50 nm over a distance of 60,000 nm is measured. The measurements yield a spin-wave group velocity as high as 2600 m s−1, which is faster than both domain wall and skyrmion motions., Short-wavelength spin waves with high group velocity are one of the key ingredients for the spin-wave based memory-logics. Here the authors demonstrate the propagation of spin waves with wavelength down to 50 nm and group velocity up to 2600 m s−1 using ferromagnetic nanowires grown on a thin Y3Fe5O12 film strip structure.

Magnetic two-dimensional materials have attracted considerable attention for their significant potential application in spintronics. In this study, we present a high-quality Fe-doped SnS2 monolayer exfoliated using a micromechanical cleavage method. Fe atoms were doped at the Sn atom sites, and the Fe contents are ∼2.1%, 1.5%, and 1.1%. The field-effect transistors based on the Fe0.021Sn0.979S2 monolayer show n-type behavior and exhibit high optoelectronic performance. Magnetic measurements show that pure SnS2 is diamagnetic, whereas Fe0.021Sn0.979S2 exhibits ferromagnetic behavior with a perpendicular anisotropy at 2 K and a Curie temperature of ~31 K. Density functional theory calculations show that long-range ferromagnetic ordering in the Fe-doped SnS2 monolayer is energetically stable, and the estimated Curie temperature agrees well with the results of our experiment. The results suggest that Fe-doped SnS2 has significant potential in future nanoelectronic, magnetic, and optoelectronic applications. 2D materials can be doped with magnetic atoms in order to boost their potential applications in spintronics. Here, the authors fabricate Fe-doped SnS2 monolayers and show that Fe0.021Sn0.979S2 exhibits ferromagnetic behaviour with perpendicular anisotropy at 2 K, and a Curie temperature of 31 K.

© 2017 American Physical Society. Magnetization reversal of interconnected kagome artificial spin ice was studied by the first-order reversal curve (FORC) technique based on the magneto-optical Kerr effect and magnetoresistance measurements. The magnetization reversal exhibits a distinct sixfold symmetry with the external field orientation. When the field is parallel to one of the nano-bar branches, the domain nucleation/propagation and annihilation processes sensitively depend on the field cycling history and the maximum field applied. When the field is nearly perpendicular to one of the branches, the FORC measurement reveals the magnetic interaction between the Dirac strings and orthogonal branches during the magnetization reversal process. Our results demonstrate that the FORC approach provides a comprehensive framework for understanding the magnetic interaction in the magnetization reversal processes of spin-frustrated systems.

It has been reported in experiments that capping layers which enhance the perpendicular magnetic anisotropy (PMA) of magnetic tunnel junctions (MTJs) induce great impact on the tunnel magnetoresistance (TMR). To explore the essential influence caused by capping layers, we carry out ab initio calculations on TMR in the X(001)|CoFe(001)|MgO(001)|CoFe(001)|X(001) MTJ, where X represents the capping layer material which can be tungsten, tantalum or hafnium. We report TMR in different MTJs and demonstrate that tungsten is an ideal candidate for a giant TMR ratio. The transmission spectrum in Brillouin zone is presented. It can be seen that in the parallel condition of MTJ, sharp transmission peaks appear in the minority-spin channel. This phenomenon is attributed to the resonant tunnel transmission effect and we explained it by the layer-resolved density of states (DOS). In order to explore transport properties in MTJs, the density of scattering states (DOSS) was studied from the point of band symmetry. It has been found that CoFe|tungsten interface blocks scattering states transmission in the anti-parallel condition. This work reports TMR and transport properties in MTJs with different capping layers, and proves that tungsten is a proper capping layer material, which would benefit the design and optimization of MTJs.

We have optimized the perpendicular magnetic anisotropy of piezoelectric/ferromagnetic and dielectric/ferromagnetic heterostructures based on Co/Pt multilayers. These hybrid systems are promising for electric field control of magnetism for applications to ultra-low power spintronics devices. Epitaxial (PbMg1/3Nb2/3O3)0.7-(PbTiO3)0.3 has been used for the piezoelectric layer and several dielectric layers (MgO, Al2O3, HfO2, Ta2O5 and TiO2) have been tested. We show that for both heterostructures perpendicular magnetic anisotropy of Co/Pt multilayers can be obtained with small coercivity.

Effective control of the domain wall (DW) motion along the magnetic nanowires is of great importance for fundamental research and potential application in spintronic devices. In this work, a series of permalloy nanowires with an asymmetric notch in the middle were fabricated with only varying the width (d) of the right arm from 200 nm to 1000 nm. The detailed pinning and depinning processes of DWs in these nanowires have been studied by using focused magneto-optic Kerr effect (FMOKE) magnetometer, magnetic force microscopy (MFM) and micromagnetic simulation. The experimental results unambiguously exhibit the presence of a DW pinned at the notch in a typical sample with d equal to 500 nm. At a certain range of 200 nm d d dependences, which may be originated from different potential well/barrier generated by the asymmetric notch with varying d.

Magnetic skyrmion, vortex-like swirling topologically stable spin configurations, is appealing as information carrier for future nanoelectronics, owing to the stability, small size and extremely low driving current density. One of the most promising applications of skyrmion is to build racetrack memory (RM). Compared to domain wall-based RM (DW-RM), skyrmion-based RM (Sky-RM) possesses quite a few benefits in terms of energy, density and speed etc. Until now, the fundamental behaviors, including nucleation/annihilation, motion and detection of skyrmion have been intensively investigated. However, one indispensable function, i.e., pinning/depinning of skyrmion still remains an open question and has to be addressed before applying skyrmion for RM. Furthermore, Current research mainly focuses on physical investigations, whereas the electrical design and evaluation are still lacking. In this work, we aim to promote the development of Sky-RM from fundamental physics to realistic electronics. First, we investigate the pinning/depinning characteristics of skyrmion in a nanotrack with the voltage-controlled magnetic anisotropy (VCMA) effect. Then, we propose a compact model and design framework of Sky-RM for electrical evaluation. This work completes the elementary memory functionality of Sky-RM and fills the technical gap between the physicists and electronic engineers, making a significant step forward for the development of Sky-RM., Comment: 10 pages, 8 figures

A comprehensive study of the magnetic skyrmion dynamics in terms of size, velocity, energy, and stability in width-varying nanotracks is reported by micromagnetic simulations. We find that the diameter of a skyrmion reduces with the decrease in the nanotrack width in the spin Hall effect (SHE)-induced skyrmion motion. Accordingly, the skyrmion energy increases giving rise to the growing instability of the skyrmion. It is also numerically demonstrated that the velocity of the skyrmion varies during the motion, since the repulsive force of the nanotrack edges acting on the skyrmion as well as the driving force created by the SHE associated with the size of the skyrmion have a joint impact on the skyrmion motion dynamics in the width-varying nanotrack. In addition, one interesting finding reveals that skyrmions with small sizes, which may be inaccessible to typical approaches by means of directly injecting a spin-polarized current, could be obtained by utilizing this structure. This finding is potential for ...

First-principles calculations are performed to investigate the magnetic anisotropy and voltage-controlled magnetic anisotropy (VCMA) in the strontium titanate (SrTiO3)-based structure. It is found that SrTiO3/Fe/Cu gives rise to an interfacial perpendicular magnetic anisotropy (PMA) of 1.3 mJ/m2. More importantly, the VCMA coefficient of this structure is 37% larger than that of the MgO-based counterpart. The microscopic mechanism is elucidated by resolving the VCMA effect to each atomic layer and each orbital hybridization. We demonstrate that the VCMA effect is not confined at the first Fe monolayer of the SrTiO3/Fe interface but extends into the second and third Fe monolayers. The origin of these phenomena can be explained with the changes of contributions to PMA from each orbital hybridization induced by redistributions of orbital occupancy under an electric field.

Magnetic skyrmions are envisioned as ideal candidates as information carriers for future spintronic devices, which have attracted a great deal of attention in recent years. Due to their topological protection, the creation and annihilation of magnetic skyrmions have been a challenging task. Here, we numerically demonstrate that a magnetic skyrmion can be created by chopping a chiral stripe domain with a static uniaxial strain/stress pulse. This mechanism not only provides a method to create skyrmions in magnetic nanostructures but also offers promising routes for designing tunable skyrmionic-mechanic devices.

Pt/Co/heavy metal (HM) tri-layered structures with interfacial perpendicular magnetic anisotropy (PMA) are currently under intensive research for several emerging spintronic effects, such as spinorbit torque, domain wall motion, and room temperature skyrmions. HM materials are used as capping layers to generate the structural asymmetry and enhance the interfacial effects. For instance, the Pt/Co/Ta structure attracts a lot of attention as it may exhibit large Dzyaloshinskii-Moriya interaction. However, the dependence of magnetic properties on different capping materials has not been systematically investigated. In this paper, we experimentally show the interfacial PMA and damping constant for Pt/Co/HM tri-layered structures through time-resolved magneto-optical Kerr effect measurements as well as magnetometry measurements, where the capping HM materials are W, Ta, and Pd. We found that the Co/HM interface plays an important role on the magnetic properties. In particular, the magnetic multilayers with a W capping layer features the lowest effective damping value, which may be attributed to the different spin-orbit coupling and interfacial hybridization between Co and HM materials. Our findings allow a deep understanding of the Pt/Co/HM tri-layered structures. Such structures could lead to a better era of data storage and processing devices., 6 pages, 5 figures, 2 tables

Until now, spintronics devices have relied on polarized currents, which still generate relatively high dissipation, particularly for nanodevices based on DW motion. A novel solution to further reduce power consumption is emerging, based on electric field (E) gating to control the magnetic state. Here, we will describe the state of the art and our recent experiments on voltage induced changes in the magnetic properties of ferromagnetic metals. A thorough description of the advances in terms of control of intrinsic properties such as magnetic anisotropy and ferromagnetic transition temperature as well as in intrinsic properties like coercive field and domain wall motion will be presented. Additionally, a section will be dedicated to the summary of the key aspects concerning the fabrication and performance of magneto-electric field-effect devices.