Torque Efficiency Research Articles

Harnessing synergy of spin and orbital currents in heavy metal/ferromagnet multilayers

Spin-orbitronics, exploiting electron spin and/or orbital angular momentum, offers a powerful route to energy-efficient spintronic applications. Recent research on orbital currents in light metals broadens the scope of spin-orbit torque (SOT). However, distinguishing and manipulating orbital torque in heavy metal/ferromagnet (HM/FM) remains a challenge, limiting the promising synergy of spin and orbital currents. Here, we design a HM/FM/FMSOC heterostructure and experimentally separate orbital torque contribution from spin torque by utilizing the distinct diffusion length of spin and orbital currents. Furthermore, we achieve the synergy of spin and orbital torques by controlling their relative strength, and obtain a 110% improvement in torque efficiency compared to the representative Pt/Co bilayer. Our findings not only contribute to a deeper understanding of SOT mechanisms and orbital current transport in HM/FM multilayers, but also highlight the promising prospect of orbital and spin torque synergy for optimizing the efficiency of next-generation spintronic devices.

Orbital torque switching in perpendicularly magnetized materials

The orbital Hall effect in light materials has attracted considerable attention for developing orbitronic devices. Here we investigate the orbital torque efficiency and demonstrate the switching of the perpendicularly magnetized materials through the orbital Hall material, i.e., Zr. The orbital torque efficiency of approximately 0.78 is achieved in the Zr orbital Hall material with the perpendicularly magnetized [Co/Pt]3 sample, which significantly surpasses that of the perpendicularly magnetized CoFeB/Gd/CoFeB sample (approximately 0.04). Such a notable difference is attributed to the different spin-orbit correlation strength between the [Co/Pt]3 sample and the CoFeB/Gd/CoFeB sample, confirmed through theoretical calculations. Furthermore, the full magnetization switching of the [Co/Pt]3 samples with a switching current density of approximately 2.6×106 A/cm2 has been realized through Zr, which even outperforms that of the W spin Hall material. Our finding provides a guideline to understand orbital torque efficiency and paves the way for developing energy-efficient orbitronic devices.

Influence of kilohertz frequency, burst duty cycle and burst duration on evoked torque, discomfort and muscle efficiency: A randomized crossover trial.

This study aimed to investigate the effects of different KFACs on evoked torque, current efficiency, and perceived discomfort. KFACs with frequencies of 1 kHz (Aussie current) and 2.5 kHz (Russian current), along with two duty cycles (10% and 20%), were randomly applied to the triceps surae muscle of healthy participants using a crossover design. The NMES intensity, NMES-evoked torque, NMES efficiency, and NMES discomfort were measured in maximal and submaximal conditions. Statistical analyses were conducted using a two-way mixed-model ANOVA with repeated measures. Forty-four participants were included. Aussie currents produced higher evoked torque and efficiency in maximal and submaximal efforts, with higher perceived discomfort in maximal effort. Although the Australian current may cause greater discomfort at maximal efforts, it matches the Russian current in perceived discomfort at submaximal levels. The 20% duty cycle produced the highest efficiency in submaximal efforts. In both maximal and submaximal efforts, the Aussie current demonstrated superior NMES efficiency, yielding higher torque with lower amplitude than the Russian current. Clinicians should take these findings into consideration when prescribing KFACs to optimize clinical outcomes.

Swift heavy ion irradiation-induced enhancement of spin–orbit torque efficiency in Pt/Co/Ta trilayers

Increasing the efficiency of spin–orbit torque (SOT) is of great interest in applications for magnetic random access memory and logic devices due to decreased energy consumption. Here, we present that the SOT efficiency of Pt/Co/Ta films with perpendicular magnetic anisotropy can be improved by swift high-energy heavy Fe11+ ion irradiation, which is an effective method to alter crystallinity, interface roughness, and defects in ferromagnet/heavy metal heterostructures. Specifically, the Pt/Co/Ta films show an optimal SOT efficiency at ion fluence around 1.0 × 1013 ions/cm2 with the largest spin Hall angles reaching 0.59, which is the largest improvement of spin Hall angle by ion irradiation compared to previous studies using light ions. We demonstrate that the increase in SOT efficiency arises from structural changes in the Pt layer due to ion irradiation-induced damage effects at proper fluence, while the decrease in SOT efficiency is mainly attributed to the restoration of Pt crystallinity induced by beam-heating effects at high fluence. This work demonstrates that an appropriate ion irradiation process could improve the SOT efficiency and the spin Hall angle, thereby providing a way to develop future SOT-based spintronic devices.

Investigation of spin-orbit torque efficiency in CuBi alloys

Investigation of spin-orbit torque efficiency in CuBi alloys

Mitigating thermal stratification in lakes/reservoirs through wind-powered air diffusers.

Thermal stratification can cause various water quality issues in large water bodies. To address this, a new wind-powered artificial mixing system is designed and experimentally tested for various Savonius rotor combinations (three-stage and four-stage rotors). These turbines directly utilize wind energy to draw air into the water column for aeration, bypassing the need for electrical conversion. The rotor performances were tested in terms of power and torque coefficients. Additionally, these rotors were tested for artificial mixing efficiencies in a specially designed water tank that can mimic thermal stratification typically observed in an actual water supply reservoir. Among the rotors, the three-stage rotor with a 60° phase shift was found to exhibit superior power and torque coefficients, achieving a power efficiency value of 0.14. As for the mixing efficiency, the four-stage rotor with a 45° phase shift excelled in mixing efficiency, reaching 95%. PRACTITIONER POINTS: A new wind-powered artificial mixing system is designed and tested for various Savonius rotor combinations. While keeping the total rotor height constant, the three-stage Savonius rotor class shows superior performance against the four-stage Savonius rotor class in terms of power and torque efficiency. Apart from the rotor performance results, the four-stage Savonius rotors show greater artificial mixing efficiency than the three-stage Savonius rotors. Single-pump/diffuser artificial destratification system exhibits better mixing efficiency than multiple-pump/diffuser systems.

Mitigation of Gilbert Damping in the CoFe/CuOx Orbital Torque System.

Charge-spin interconversion processes underpin the generation of spin-orbit torques in magnetic/nonmagnetic bilayers. However, efficient sources of spin currents such as 5d metals are also efficient spin sinks, resulting in a large increase of magnetic damping. Here we show that a partially oxidized 3d metal can generate a strong orbital torque without a significant increase in damping. Measurements of the torque efficiency ξ and Gilbert damping α in CoFe/CuOx and CoFe/Pt indicate that ξ is comparable in the two systems. The increase in damping relative to a single CoFe layer is Δα < 0.002 in CoFe/CuOx and Δα ≈ 0.005-0.02 in CoFe/Pt, depending on CoFe thickness. We ascribe the nonreciprocal relationship between Δα and ξ in CoFe/CuOx to the small orbital-spin current ratio generated by magnetic resonance in CoFe and the lack of an efficient spin sink in CuOx. Our findings provide new perspectives on the efficient excitation of magnetization dynamics via the orbital torque.

Sizing and simulation of modular electric off-road vehicle using Scilab Xcos

Abstract As a sustainable transportation alternative, particularly in the realm of off-road vehicles, electric vehicles are rapidly gaining popularity. Despite the limitations that records have imposed including short-lived ranges and low speed as opposed to conventional vehicles, their eco-friendly nature and efficiency renders them to be appealing. The ongoing technological leaps in motor and battery technologies have improved the standing of long-distance electric vehicles, optimizing their performance by tailoring motors and batteries to suit specific regions and driving patterns. This study aims to size the motor and battery components of an off-road modular vehicle using Scilab Xcos, open-source software. The data obtained from the driving data accessed by driving the electric vehicle around 1 km of Dhulikhel is used as input for the simulation. The output of the simulation is used to understand the requirements of the motor and battery specifications. The motor was able to provide a maximum torque of 100 Nm and a nominal power of 10kW with peak power of 25 kW, while the battery was able to provide a battery power of 16kWh. The design went through theoretical validation and was compared against the established experimental data of the vehicle. Altogether, results affirm that the customized model aligns with the vehicle’s performance requirements by delivering adequate power, torque, and energy efficiency.

Composition dependence of the orbital torque in [formula omitted] and [formula omitted] alloys: Spin-orbit correlation analysis

The spin-orbit correlation in ferromagnet (FM) is an important factor that affects the orbital torque efficiency in the FM. We investigate the spin-orbit correlation in FM alloys, CoxFe1−x and NixFe1−x, with varying their composition. We find spots where the spin-orbit correlation is significantly strong near the Fermi surface in Co0.125Fe0.875, Co0.25Fe0.75, Co0.875Fe0.125, and Ni0.5Fe0.5, while no such spot appears in Co0.5Fe0.5, and Ni0.75Fe0.25. These results imply that in the former structures, the orbital polarized current injected into these spots can provide a strong torque to the magnetization of the FM through the orbital torque mechanism. These results also show that even in the same alloy system, the difference in alloy composition can lead to different orbital torque efficiency.

A study of rare-earth magnet profiles for torque ripple improvement of axial flux permanent magnet machine

Purpose The purpose of this study is to reduce the cogging torque in axial flux permanent magnet (AFPM) machine using optimal magnet shape. Design/methodology/approach This study analyzes different magnet shapes for AFPM machine performance enhancement. Three-dimensional (3D) finite element analysis is performed to see the effects of pole shaping on the cogging torque of the AFPM machine. Findings The magnetic pole shape has a significant effect on cogging torque and overall efficiency. The conventional model has the highest torque whereas the conventional skewing affected cogging torque positively and significantly reduced the cogging torque. The combination of skewing the pole along with face curving is more effective and decreases the cogging torque from 3.88 Nm to 1.5 Nm. Originality/value Rare-earth magnets are the most expensive and important part of AFPM machines. Shape and volume optimization of rare-earth magnets is crucial for the performance of AFPM machines. The research aims to analyze the different permanent magnet designs for performance improvement of the AFPM machine. Conventional flat top trapezoidal, curved-top and skewed-magnet shapes are analyzed and the performance of the AFPM machine is compared with different magnet shapes. Curved-top shape and skewed magnet significantly reduce the cogging torque. Furthermore, a combination of curved-top shape and skew magnet shape is proposed to reduce the cogging torque further and improve the AFPM machine’s overall performance. Newly proposed magnet profile gives skewed curve magnet shapes which reduce the cogging torque further. 3D finite element analysis has been used to analyze the single-sided AFPM with all four different magnet shapes. The research focuses on single-sided AFPM machines, but the results are also valid for double-sided AFPM machines and can be extended to other topologies of AFPM machines.

Spin–orbit torque effect in silicon-based sputtered Mn3Sn film

Abstract Noncollinear antiferromagnet Mn3Sn has shown remarkable efficiency in charge–spin conversion, a novel magnetic spin Hall effect, and a stable topological antiferromagnetic state, which has resulted in great interest from researchers in the field of spin–orbit torque. Current research has primarily focused on the spin–orbit torque effect of epitaxially grown noncollinear antiferromagnet Mn3Sn films. However, this method is not suitable for large-scale industrial preparation. In this study, amorphous Mn3Sn films and Mn3Sn/Py heterostructures were prepared using magnetron sputtering on silicon substrates. The spin-torque ferromagnetic resonance measurement demonstrated that only the conventional spin–orbit torque effect generated by in-plane polarized spin currents existed in the Mn3Sn/Py heterostructure, with a spin–orbit torque efficiency of 0.016. Additionally, we prepared the perpendicular magnetized Mn3Sn/CoTb heterostructure based on amorphous Mn3Sn film, where the spin–orbit torque driven perpendicular magnetization switching was achieved with a lower critical switching current density (3.9×107 A/cm2) compared to Ta/CoTb heterostructure. This research reveals the spin–orbit torque effect of amorphous Mn3Sn films and establishes a foundation for further advancement in the practical application of Mn3Sn materials in spintronic devices.

RSM based optimization of lambda and mixed fuel concentration parameters of an LTC mode engine

In this study, the effects of lambda and premixed ratio (PR) parameters on the response parameters of an engine operating in LTC (low temperature combusiton) mode is investigated and optimized using a hybrid method. RSM (response surface method), which is a combination of experimental and statistical method, is used as hybrid method. Depending on the variable parameters of lambda and PR, an experimental set was created with CCD (central composite design) and experiments were performed. The effects of the variable parameters on the response parameters were investigated and evaluated in detail on the generated counter graphs, optimization of the variable parameters was carried out. As lambda increased, a decrease in engine torque and thermal efficiency values, and improvements in CO2 and NOx emissions were observed. As PR increased, thermal efficiency and specific fuel consumption values worsened. The optimum premixed ratio was determined as 33.619 % and lambda value as 2.576. At these conditions, the values of response parameter were obtained as torque 12.115 Nm, BSFC 346.764 g/kWh, ITE 21.447 %, CA10 3.503, CA50 8.005, CO 0.169 %, HC 191.467 ppm, CO2 5.301 %, NOx 404.564 ppm and soot 12.687 %. The optimization desirability value was determined as 0.665 and strengthened the goodness of the optimization.

Pengaruh Variasi Pembebanan Terhadap Performansi Mesin Diesel Single-Fuel Berbahan Bakar Dexlite dan Liquified Petroleum Gas

Liquified Petroleum Gas (LPG) is an environmentally friendly alternative fuel, it would be a shame if it were not utilized. By making modifications to the diesel engine, it turns out that LPG can be used as a substitute for fuel oil. This research aims to determine the performance of a single-fuel diesel engine using Dexlite and 3 kg LPG. The method in this research is experimental research. Data was taken three times in each experiment with different load variations, then processed to obtain values for engine speed, torque, power, SFC and thermal efficiency. The research results show that the maximum torque value for dexlite and LPG is 22.4375 N.m. The maximum power value for dexlite and LPG is 3.9924 kW. The minimum SFC value for dexlite is 1.3089 kg/kW.hour while LPG is 0.9481 kg/kW.hour. The maximum thermal efficiency value for dexlite is 64.03% while for LPG it is 80.8%. The results of this research show that the torque and power values for each fuel have the same value, this is because the engine speed and load are the same. However, the SFC value and thermal efficiency of each fuel have different values, where the SFC value of 3 kg LPG is lower than Dexlite and the thermal efficiency value of 3 kg LPG is higher than Dexlite.

Enhanced Spin-Orbit Torque Efficiency in Platinum-Gadolinium Oxide Nanocomposite Films.

Spin-orbit torque (SOT) has emerged as an effective means of manipulating magnetization. However, the current energy efficiency of SOT operation is inefficient due to low damping-like SOT efficiency per unit current bias. In this work, we dope conventional rare earth oxides, GdOy, into highly conductive platinum by magnetron sputtering to form a new group of spin Hall materials. A large damping-like spin-orbit torque (DL-SOT) efficiency of about 0.35 ± 0.013 is obtained in Pt0.70(GdOy)0.30 measured by the spin-torque ferromagnetic resonance (ST-FMR) technique, which is about five times that of pure Pt under the same conditions. The substantial enhancement of the spin Hall effect is revealed by theoretical analysis to be attributed to the strong side jump induced by the rare earth oxide GdOy impurities. Moreover, this large DL-SOT efficiency contributes to a low critical switching current density (8.0 × 106 A·cm-2 in the Pt0.70(GdOy)0.30 layer) in current-induced magnetization switching measurements. This systematic study on SOT switching properties suggests that Pt1-x(GdOy)x is an attractive spin current source with large DL-SOT efficiency for future SOT applications and provides another idea to regulate the spin Hall angle.

Observation of Long-Range Current-Induced Torque in Ni/Pt Bilayers.

The generation of current-induced torques through the spin Hall effect in Pt has been key to the development of spintronics. In prototypical ferromagnetic-metal/Pt devices, the characteristic length of the torque generation is known to be about 1 nm due to the short spin diffusion length of Pt. Here, we report the observation of a long-range current-induced torque in Ni/Pt bilayers. We demonstrate that when Ni is used as the ferromagnetic layer, the torque efficiency increases with the Pt thickness, even when it exceeds 10 nm. The torque efficiency is also enhanced by increasing the Ni thickness, providing evidence that the observed torque cannot be attributed to the spin Hall effect in the Pt layer. These findings, coupled with our semirealistic tight-binding calculations of the current-induced torque, suggest the possibility that the observed long-range torque is dominated by the orbital Hall effect in the Pt layer.

Enhanced Spin–Orbit Torque Efficiency by the Insertion of a Thin NiO Underlayer in Pt/Co/Ta Films

Enhanced Spin–Orbit Torque Efficiency by the Insertion of a Thin NiO Underlayer in Pt/Co/Ta Films

Efficient magnetization switching induced by spin–orbit torque in perpendicularly magnetized Mn1+xCo2−xAl Heusler alloys

Perpendicularly magnetized Co-based Heusler alloys are promising candidates in high-performance spintronic devices. However, there is a contradiction between thermal stability and damping-like spin–orbit torque (SOT) efficiency in Co-based Heusler alloys with interface-induced perpendicular magnetic anisotropy (PMA). Here, we present epitaxially grown perpendicularly magnetized Mn1+xCo2−xAl (MCA) Heusler alloys through tetragonal distortion. Ferrimagnetism and distortion-induced PMA are obtained in MCA Heusler alloys. A large effective spin Hall angle (θeff) up to 0.33 is experimentally demonstrated in Pt/MCA bilayers, markedly surpassing that in conventional Pt/FM bilayers. Consequently, SOT-induced efficient magnetization switching is realized in Pt/MCA bilayers, with a critical switching current density (Jc) as low as 4 × 107 A/cm2. The large θeff and high SOT efficiency would be attributed to the staggered magnetic exchange torques in the ferrimagnetic MCA Heusler alloys. These findings demonstrate that perpendicularly magnetized ferrimagnetic MCA Heusler alloys are highly promising for high-density SOT-magnetic random-access memory with superior thermal stability and low power consumption.

Enhancing speed–torque response and efficiency of Modern Utility Hybrid Renewable Energy Vehicles (MUHREVs) through inverted decoupler control strategy

Enhancing speed–torque response and efficiency of Modern Utility Hybrid Renewable Energy Vehicles (MUHREVs) through inverted decoupler control strategy

Enhanced torque efficiency in ferromagnetic multilayers by introducing naturally oxidized Cu

Spin–orbit torque (SOT) in the heavy elements with a large spin–orbit coupling (SOC) has been frequently used to manipulate the magnetic states in spintronic devices. Recent theoretical works have predicted that the surface oxidized light elements with a negligible SOC can yield a sizable orbit torque (OT), which plays an important role in switching the magnetization. Here, we report anomalous-Hall-resistance and harmonic-Hall-voltage measurements on perpendicularly magnetized Ta/Cu/[Ni/Co]5/Cu-CuOx multilayers. Both torque efficiency and spin-Hall angle of these multilayers are largely enhanced by introducing a naturally oxidized Cu-CuOx layer, where the SOC is negligible. Such an enhancement is mainly due to the collaborative driven of the SOT from the Ta layer and the OT from the Cu/CuOx interface and can be tuned by controlling the thickness of Cu-CuOx layer. Compared to the Cu-CuOx-free multilayers, the maximum torque efficiency and spin-Hall angle were enhanced by a factor of ten, larger than most of the reported values in the other heterostructures.

Study on Anomalous Hall Effect and Spin-Orbit Torque Effect of TbCo-Based Multilayer Films.

The anomalous Hall effect and spin-orbit torque of TbCo-based multilayer films have been methodically studied in recent years. Many properties of the films can be obtained by the anomalous Hall resistance loops of the samples. We report on the effects of a structure composed of two heavy metals as the buffer layers on the anomalous Hall resistance loops of TbCo-based multilayers at different temperatures. The results showed that the coercivity increases dramatically with decreasing temperature, and the samples without perpendicular magnetic anisotropy at room temperature showed perpendicular magnetic anisotropy at low temperatures. We quantified the spin-orbit torque efficiency and Dzyaloshinskii-Moriya interaction effective field size of the films W/Pt/TbCo/Pt at room temperature by measuring the loop shift of anomalous Hall resistance. The results showed that the study of anomalous Hall resistance loops plays an important role in the study of spintronics, which can not only show the basic properties of the sample, but can also obtain other information about the sample through the shift of the loops.