Logic Devices Research Articles

Magnetization switching and performance of an optimized bicomponent multiferroic nanomagnet

Achieving complete magnetization switching is a significant challenge in the electrical control of magnetic devices. In this paper, we propose a structure called bicomponent multiferroic nanomagnet (BMN) to study strain-mediated magnetization switching behavior. The BMN consists of a complete piezoelectric layer and a magnetostrictive layer made of bicomponent magnetic materials. Our team successfully developed a dynamic model for the magnetization of BMNs. By micromagnetic simulation, the results show that the strict requirements for a precise applied voltage period can be overcome in such a BMN, and a 180° magnetization switching can be achieved with only a square-wave voltage signal and a pulse width (tth) larger than 0.5 ns, given that the amplitude of the voltage is 60 mV. In addition, we also investigated the tolerance window of material composition and geometry, and proved that BMNs have sufficient error margins and the switching rate of BMNs can reach 1.67 GHz within the error margins at room temperature. Our proposed BMN device has a simple structure and low energy consumption as it does not require precise piezoelectric layer design or stringent voltage clocking requirements. The energy consumption per switching is only 7.3 aJ. These findings provide significant guidance for the design of nanomagnetic logic and memory devices and lay a strong foundation for the application of strain-mediated magnetization switching technology.

An all-in-one optoelectronic logic device with self-distinguishable dual-band photoresponse

An all-in-one optoelectronic logic device with self-distinguishable dual-band photoresponse

Interfacial Magnetic Anisotropy Controlled Spin Pumping in Co60Fe20B20/Pt Stack

Controlled spin transport in magnetic stacks is required to realize pure spin current-driven logic and memory devices. The control over the generation and detection of the pure spin current is achieved by tuning the spin to charge conversion efficiency of the heavy metal interfacing with ferromagnets. Here, we demonstrate the direct tunability of spin angular momentum transfer and thereby spin pumping, in CoFeB/Pt stack, with interfacial magnetic anisotropy. The ultra-low thickness of the CoFeB thin film by tilting the magnetization from in-plane to out-of plane direction due to interfacial anisotropy from higher thickness of CoFeB thin film. The ferromagnetic resonance measurements are performed to investigate the magnetic anisotropy and spin pumping in CoFeB/Pt stacks. We clearly observe tunable spin pumping effect in the CoFeB/Pt stacks with varying CoFeB thicknesses. The spin current density, with varying ferromagnetic layer thickness, is found to increase from 1.10[Formula: see text]MA/m2 to 2.40[Formula: see text]MA/m2, with increasing in-plane anisotropy field. Such interfacial anisotropy-controlled generation of pure spin current can potentially lead to next-generation anisotropic spin current-controlled spintronic devices.

Non-volatile voltage-controlled magnetization in single-phase multiferroic ceramics at room temperature

Single-phase multiferroics (MFs) exhibiting ferroelectricity and ferromagnetism and the strong magnetoelectric (ME) coupling effect at room temperature are seen as key to the development of the next-generation of spintronic devices, multi-state memories, logic devices and sensors. Herein, the single-tetragonal phase (1–x) (Sr0·3Bi0·35Na0·329Li0.021)TiO3-xBiFeO3 (x = 0.2 or 0.4) system was designed to study the intrinsic ME coupling effect at room temperature and high frequencies. The polarization arises from the cooperative displacement of both Fe3+ and Ti4+ relative to the oxygen sublattice in the tetragonally distorted perovskite structure, and the magnetization stems from indirect exchange magnetic interaction between adjacent iron ions. A switchable voltage-controlled magnetization was confirmed by a change of the coercive magnetic field, Hc, and remnant magnetization, Mr, in the x = 0.4 component subjected to an external electric field at room temperature and was possibly attributed to a strain-mediated ME coupling effect. In addition, resonance behaviours of the complex magnetic permeability and complex dielectric permittivity in the GHz band indicate that this ME effect is intrinsic in nature and could broaden the applications of multiferroics to devices operating at microwave frequencies.

Spin–orbit torque reconfigurable diffraction gratings

Spin–orbit torque (SOT) provides a convenient, fast, and efficient way to switch the magnetization and has been applied in memory, logic, and microwave devices. Here, we report the application of SOT in the spatial modulation of the optical field. We construct a diffraction grating composed of perpendicularly magnetized current channels that can be switched using the SOT current pulses, and the resulting periodic magnetization patterns are transferred into the polarization modulation of light through the magneto-optical effect. We demonstrate that the periodic structures and diffraction peaks of the grating can be reconfigured electrically. These results would open up an avenue to the application of the state-of-the-art spintronic technologies in fast tunable diffractive optics.

Giant Spin-Orbit Induced Magnon Nonreciprocity in Ultrathin Ferromagnets.

The propagation characteristics of fermionic and bosonic quasiparticles determine the fundamental transport properties of solids and are of great technological relevance for designing logic devices. In particular, nonreciprocity, which describes that a quasiparticle flows preferably along a certain direction of a symmetry path, is an essential requirement to realize logic architectures, e.g., switches, diodes, transistors, etc. Here we introduce a mechanism, which leads to giant nonreciprocity of ultrafast terahertz magnons in ferromagnetic films with a large spin-orbit coupling. The mechanism is based on the competition between the exchange and spin-orbit scattering. We anticipate that the effect can be used to excite nonreciprocal or even unidirectional magnons in a large class of ultrathin films and nanostructures grown on substrates with a large spin-orbit coupling.

Preparation and optoelectronic performance of two-dimensional MoSe2/WSe2 lateral and vertical heterostructures

Two-dimensional materials Transition Metal Dichalcogenides (TMDs) are a novel type of semiconductor material with tunable bandgap and atomic-level thickness. Different TMDs can be flexibly combined to form heterostructures with distinct properties. In this paper, we have prepared two-dimensional MoSe2/WSe2 vertical and lateral heterostructures by using CVD and a combination of PVD and CVD, respectively. Subsequently, the structure, electronic and optoelectronic properties of these two types of heterostructures were characterized. The results indicate that field-effect transistors based on single-layer MoSe2/WSe2 lateral heterostructures, and single-layer WSe2/multi-layer MoSe2 and single-layer MoSe2/multi-layer WSe2 vertical heterostructures exhibit significant rectification effects. The in-plane monolayer MoSe2/WSe2 heterostructure devices exhibit the on/ff ratio of up to 104, and the monolayer-multilayer vertical heterostructure reaching 106, significantly outperforming most known devices of the same type. Moreover, the optical response of both in-plane and vertical heterostructures field-effect transistors reach 10 ms. Our research findings offer pathways for the flexible selective growth of in-plane and vertical heterostructures based on TMDs, and provide insights into achieving diverse performance in logic devices.

Shape-influenced non-reciprocal transport of magnetic skyrmions in nanoscale channel

Abstract Skyrmions, with their vortex-like structures and inherent topological protection, play a pivotal role in developing innovative low-power memory and logic devices. The efficient generation and control of skyrmions in geometrically confined systems are of paramount importance for the advancement of skyrmion-based spintronic devices. In this study, we focus on investigating the non-reciprocal transport behavior of skyrmions and their interactions with boundaries of various shapes. The shape of the notch structure in the nanotrack significantly impacts the dynamic behavior of magnetic skyrmions. Through micromagnetic simulation, we explore the non-reciprocal transport properties of skyrmions in nanowires with different notch structure.

Electrical Detection and Nucleation of a Magnetic Skyrmion in a Magnetic Tunnel Junction Observed via Operando Magnetic Microscopy.

Magnetic skyrmions are topological spin textures which are envisioned as nanometer scale information carriers in magnetic memory and logic devices. The recent demonstrations of room temperature skyrmions and their current induced manipulation in ultrathin films were first steps toward the realization of such devices. However, important challenges remain regarding the electrical detection and the low-power nucleation of skyrmions, which are required for the read and write operations. Here, we demonstrate, using operando magnetic microscopy experiments, the electrical detection of a single magnetic skyrmion in a magnetic tunnel junction (MTJ) and its nucleation and annihilation by gate voltage via voltage control of magnetic anisotropy. The nucleated skyrmion can be manipulated by both gate voltages and external magnetic fields, leading to tunable intermediate resistance states. Our results unambiguously demonstrate the readout and voltage controlled write operations in a single MTJ device, which is a major milestone for low power skyrmion based technologies.

Manipulating topological charge of nested skyrmion bags by microwave magnetic fields

Nested skyrmion bags, as magnetic solitons with arbitrary integer topological charges (Q), hold potential for applications in data encoding. A crucial issue is the local manipulation of skyrmions within nested skyrmion bags to control the total Q. In this study, we explore different possible ground states and resonant excitation spectra of nested skyrmion bags through micromagnetic simulations. More importantly, we demonstrate that the manipulation of the Q of nested skyrmion bags can be achieved by using microwave magnetic fields, i.e., the inner, middle, and outer skyrmions within the nested skyrmion bags are selectively excited by using the diverse out-of-plane excitation modes. By calculating the energy of skyrmions, we further analyze the relationship between the annihilation of skyrmions at different positions and the out-of-plane microwave magnetic fields. Our findings present a promising approach for manipulating the Q of nested skyrmion bags, potentially advancing their application in storage and logic devices.

Growth of multiferroic γ-BaFe2O4 thin films by Pulsed Electron Deposition technique

Multiferroic materials have attracted significant attention due to their potential to revolutionize logic and memory devices by reducing energy consumption or increasing information density. Barium monoferrite (γ-BaFe2O4 or BaFeO) is a promising lead- and bismuth-free multiferroic material with a stuffed tridymite-like structure, exhibiting both ferroelectricity and antiferromagnetism at room temperature. BaFeO thin films with engineered grain orientation, composition, elastic strain, and magnetic interlayer couplings could open new avenues for novel devices. However, synthesizing the stoichiometric "1–2–4" phase in the BaO-Fe2O3 system remains a challenge. This study focuses on the deposition of pure and crystalline γ-BaFe2O4 thin films using the Pulsed Electron Deposition (PED) method. An analysis of the plasma plume revealed that two main mechanisms govern the dynamics of BaFeO deposition: a congruent ablation process occurring far from thermodynamic equilibrium and an incongruent low-energy evaporation process. The regions of the film with maximized ablative/evaporative ratios are free from the secondary Ba2Fe2O5 phase, suggesting that the thermal evaporative contribution is the primary factor responsible for the out-of-stoichiometry composition. The influence of the substrate type on the structural properties of BaFeO films was also evaluated. It was confirmed that (h00)-oriented BaFeO tends to grow on amorphous quartz and polycrystalline Pt-coated quartz in the 700–800°C temperature range. Conversely, the growth on SiO2/Si leads to the preferential grain orientation along the (0k0) and (0kl) directions by increasing the temperature. These findings demonstrate the potential of PED for producing high-quality γ-BaFe2O4 polycrystalline thin films. A fully heteroepitaxial (h00)-BaFeO/(111)-MgO system was even achieved by depositing on a single-crystal MgO substrate. This unprecedented result paves the way for utilizing such thin films in multiferroic applications, where phase purity, structural orientation, and defect-free structures can be exploited to enhance the magnetoelectric properties of the device.

Implementation of EnDat Interface Master Using Configurable Logic Block in MCU

In this study, we propose an implementation method of the Encoder Data (EnDat) interface master for slave encoders using only a configurable logic block (CLB) and a serial peripheral interface (SPI) integrated into microcontroller units. By programming the CLB device to execute logic functions and finite state machines designed for the EnDat interface master operation, we realize the EnDat and SPI clocks that are required for the EnDat interface master operation. This approach is cost-efficient because additional hardware components, such as a field-programmable gate array or a complex programmable logic device, are unnecessary for the master implementation. We build a one-axis feed drive system that is powered by an AC motor and equipped with an EnDat linear encoder for measuring table speed and position. By performing various experiments for table position and speed control based on the built feed drive system, we verify the performance and practical usefulness of the implemented EnDat interface master. The maximum EnDat clock frequency without the propagation delay compensation is achieved by 2 MHz, which can cope with 16 kHz control cycle frequency. The usefulness is demonstrated by showing the table speed and position control performance that are acceptable in real applications.

Optical Modulation of MoTe2/Ferroelectric Heterostructure via Interface Doping.

Optical modulation through interface doping offers a convenient and efficient way to control ferroelectric polarization, thereby advancing the utilization of ferroelectric heterostructures in nanoelectronic and optoelectronic devices. In this work, we fabricated heterostructures of MoTe2/BaTiO3/La0.7Sr0.3MnO3 (MoTe2/BTO/LSMO) and demonstrated opposite ultraviolet (UV) light-induced polarization switching behaviors depending on the varied thicknesses of MoTe2. The thickness-dependent band structure of MoTe2 film results in interface doping with opposite polarity in the respective heterostructures. The polarization field of BTO interacts with the interface charges, and an enhanced effective built-in field (Ebi) can trigger the transfer of massive UV light-induced carriers in both MoTe2 and BTO films. As a result, the interplay among the contact field of MoTe2/BTO, the polarization field, and the optically excited carriers determines the UV light-induced polarization switching behavior of the heterostructures. In addition, the electric transport characteristics of MoTe2/BTO/LSMO heterostructures reveal the interface barrier height and Ebi under opposite polarization states, as well as the presence of inherent in-gap trap states in MoTe2 and BTO films. These findings represent a further step toward achieving multifield modulation of the ferroelectric polarization and promote the potential applications in optoelectronic, logic, memory, and synaptic ferroelectric devices.

Nonreciprocal magnonic directional coupler based on metal-coated YIG adjacent stripes

Unidirectional information transport is often realized in magnonic application using the filters, isolators, and circulators. In this Letter, we propose the simple design of the unidirectional magnonic coupler, which is realized as a laterally coupled yttrium–iron–garnet waveguide coated with a metal layer. We experimentally discover and numerically confirm that the proposed structure can exhibit unidirectional coupling, which can be easily controlled by the direction of the external magnetic field. At the same time, we show how the dynamic magnetization profile of the spin wave is varied with the change in the propagation direction to the opposite along the coupler. Brillouin light scattering reveals the variation of the spatial spin-wave profile, which is then used to extract the value of the coupling length. The experimental results are in good agreement with the results of the coupling length estimation from two methods: eingenmode analysis and Landau–Lifshits–Gilbert solution in parallel with the Maxwell equations. This opens up alternative ways to fabricate the non-reciprocal magnonic devices. In particular, we consider the operation of the unidirectional magnonic coupler as a multi-regime logic device.

Simulation and FPGA based Implementation of PI and Fuzzy Controllers for Cascaded Asymmetric Multilevel Inverter

The main objective of this work is to improve the performance of Multilevel Inverter by using the novel LS-PD- PWM and controlling technique instead of the existing approach. The proposed work focus on closed loop controller such as existing PI and Fuzzy Logic Controller for resistive load with Multilevel Inverter. The proposed Asymmetric fifteen level Inverter offers less THD and high frequency than the Asymmetric nine level inverter. Asymmetric multilevel inverter is used to reduce the switching losses and THD. In this work is the generation and implementation of Pulse Width Modulation (PWM) techniques using Field Programmable Gate Array (FPGA) for Multilevel Inverter. PWM can be generated via Microprocessors, Microcontroller, FPGA and DSP Processors. Higher density Programmable Logic Devices (PLD) such as FPGAs can be used to amalgamate large amounts of logic into a single Integrated. Pulse width modulation (PWM) is generally used in power converter control. To generate LS-PD- PWM by using FPGA, this occupies less memory capacity and accurate than conventional one. An efficient PWM generation technique is performed using FPGA for lower frequency applications. Simulation and synthesis is done by ModelSim6.3c and Xilinx10.1. Further, the Implementation is carried out by FPGA Spartan3 Xc3s50. Key Word: PWM, FPGA, PLD (Programmable Logic Devices), LS-PD-PWM

Zero-field spin wave turns

Spin-wave computing, a potential successor to CMOS-based technologies, relies on the efficient manipulation of spin waves for information processing. While basic logic devices such as magnon transistors, gates, and adders have been experimentally demonstrated, the challenge for complex magnonic circuits lies in steering spin waves through sharp turns. In this study, we demonstrate with micromagnetic simulations and Brillouin light scattering microscopy experiments, that dipolar spin waves can propagate through 90° turns without distortion. The key lies in carefully designed in-plane magnetization landscapes, addressing challenges posed by anisotropic dispersion. The experimental realization of the required magnetization landscape is enabled by spatial manipulation of the uniaxial anisotropy using corrugated magnonic waveguides. The findings presented in this work should be considered in any magnonic circuit design dealing with anisotropic dispersion and spin wave turns.

Coexistence of analog and digital memristive behaviors in MoO3 based devices for artificial synaptic and logic display applications

In-memory logic operations and neuromorphic computing inspired by the brain based on memristors are promising computing modes that can improve computational efficiency and avoid additional power consumption. However, implementing these two functions within the memristor same cell is often limited by the flexible conversion between digital and analog memristive behaviors. In this work, a memristive device with Ag/MoO3/Ti structure was developed using hydrothermal methods, which presents the evolution from capacitance-coupled memristive effect to self-rectifying non-zero crossing analog memristive behavior and then to digital memristive effect by adjusting the amplitude of applied voltage. Under low voltage region (Vamplitude ≤ 1.2 V), the non-zero crossing analog memristive effect with self-rectifying behavior is mainly attributed to the potential barrier at the interface and built-in electric field, while the digital memristive effect under high voltage region (Vamplitude ≥ 1.5 V) is mainly attributed to the formation and fracture of Ag conductive filaments (CFs). Moreover, the mechanism for the non-zero-crossing characteristic of device was proven by parallel connection of memristors and capacitors. Finally, the artificial synaptic and logic display functions were implemented using the as-prepared memristive unit. Therefore, this work provided guidance for understanding the non-zero-crossing memristive effect and the development of high-density multifunctional devices.

Effect of metal insertion on the magnetic properties and anomalous Hall effect in MgO/CoFeB/Ta/MgO films

CoFeB-based nano-magnetic multilayers can be applied in magnetic sensors, magnetic random access memory and other logic devices, which have attracted wide attention. The magnetic properties and interface structure of the magnetic multilayers still need further research for future applications. The effects of Pt insertion on the perpendicular magnetic anisotropy (PMA) and the anomalous Hall effect (AHE) of MgO/CoFeB/Pt/Ta/MgO multilayers were studied. It is found that the sample with 0.2 nm Pt insertion at the CoFeB/Ta interface and annealed at 250 °C can transform the films from in-plane magnetic anisotropy to PMA. The effective magnetic anisotropy K eff can reach 1.82 × 106 erg cm−3. The Pt insertion and annealing heat treatment can promote the migration of oxygen from MgO at the top layer to CoFeB/Ta interface and combine with Fe to generate iron oxide, and improve the orbital hybridization of Fe 3d and O 2p, thus successfully inducing the PMA of the film samples. In addition, Pt insertion and annealing treatment can improve the side-jump mechanism and the skew scattering mechanism which contribute to the AHE. This work provides guidance for the application of PMA materials in magnetic sensor and memory devices.

Parametric excitations of coupled nanomagnets

We demonstrate that parametrically excited eigenmodes in nearby nanomagnets can be coupled to each other. Both positive (in-phase) and negative (anti-phase) couplings can be realized by a combination of appropriately chosen geometry and excitation field frequency. The oscillations are sufficiently stable against thermal fluctuations. The phase relation between field-coupled nanomagnets shows a hysteretic behavior with the phase relation being locked over a wide frequency range. We envision that this computational study lays the groundwork to use field-coupled nanomagnets parametrons as building blocks of logic devices, neuromorphic systems of Ising machines.

Interface Effect on the Out‐of‐Plane Spin‐Orbit Torque in the Ferromagnetic CoPt Single Layers

AbstractField‐free switching of a perpendicularly magnetized heavy metal/ferromagnetic metal bilayer or single alloy layer through spin‐orbit torque (SOT) provides a potential way for next‐generation spintronic devices with fast speed and high efficiency. Here, a sizable symmetry dependence of field‐free magnetization switching via an out‐of‐plane torque in CoxPt100−x single layers is reported. It is found that the sign of in‐plane SOT in CoxPt100−x when x ≤ 25 is positive. However, it changes to negative when x > 25, while the out‐of‐plane SOT changes its sign when x > 30. The polarized neutron reflectometry measurement further suggests an interface layer with rich Pt content near the substrate, which could have a strong interface effect on the out‐of‐plane SOT. The sign of the out‐of‐plane SOT, and then the polarity of the field‐free magnetization switching, is determined by the competition between the out‐of‐plane torques arising from the bulk and interface parts in the CoxPt100−x single layers. It is expected that such interface effect of the out‐of‐plane torque is desirable to the applications in spin logic devices using symmetry dependence of field‐free magnetization switching in the ferromagnetic CoPt single layers.