Current-induced Effect Research Articles

Current-induced spin polarization and spin Hall effect in III-V compounds two-dimensional materials

Current-induced spin polarization and spin Hall effect in III-V compounds two-dimensional materials

Unraveling the Stray Current-Induced Interfacial Transition Zone (ITZ) Effect on Sulfate Corrosion in Concrete

The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion; however, the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear. To address this issue, novel sulfate transport and mesoscale splitting tests were designed, with a focus on considering the differences between the interfacial transition zone (ITZ) and cement matrix. Under the influence of stray current, the ITZ played a pivotal role in regulating the transport and mechanical failure processes of sulfate attack, while the tortuous and blocking effects of aggregates almost disappeared. This phenomenon was termed the “stray current-induced ITZ effect.” The experimental data revealed that the difference in sulfate ion transport attributed to the ITZ ranged from 1.90 to 2.31 times, while the difference in splitting strength ranged from 1.56 to 1.64 times. Through the real-time synchronization of splitting experiments and microsecond-responsive particle image velocimetry (PIV) technology, the mechanical properties were exposed to the consequences of the stray current-induced ITZ effect. The number of splitting cracks in the concrete increased, rather than along the central axis, which was significantly different from the conditions without stray current and the ideal Brazilian disk test. Furthermore, a sulfate ion mass transfer model that incorporates reactivity and electrodiffusion was meticulously constructed. The embedded finite element calculation exhibited excellent agreement with the experimental results, indicating its reliability and accuracy. Additionally, the stress field was determined utilizing analytical methods, and the mechanism underlying crack propagation was successfully obtained. Compared to the cement matrix, a stray current led to more sulfates, more microstructure degradation, and greater increases in thickness and porosity in the ITZ, which was considered to be the essence of the stray current-induced ITZ effect.

Mitigation of Screening Current-Induced Magnetic Field Effect in HTS Dipole Magnet Based on Coated Conductors: Overshooting and Shim Coil Study

Mitigation of Screening Current-Induced Magnetic Field Effect in HTS Dipole Magnet Based on Coated Conductors: Overshooting and Shim Coil Study

On the spectral wave climate of the French Atlantic Ocean

The accurate description of wave climate at different spatio-temporal scales requires the application of advanced statistical models together with a good knowledge of geophysical processes. Furthermore, accurate modelling of multimodal sea states is of primary importance for most of offshore and coastal activities, such as wave energy device optimization, maritime design practice and for safety at sea. The present manuscript is conceived within this scientific framework proposing to assess wave climate of a complex area of French Atlantic Ocean bordering seas. The main “Spectral Climatology Types” of the area are identified as resulting of defined combinations of wave systems detected through directional spectra and partitioned wave systems analysis. The presence of swell systems is evaluated quantitatively on the whole area, characterized by different regimes of multimodal sea-states at strong regional variability and put into relation with main meteorological forcing active on the area at different spatial scales. Celtic Sea exhibits a marked regional characterization with a prevalence of multimodal conditions given by different combination of wave systems with increasing contribution of swell systems moving from North-West to South. A significant presence of crossing sea states is observed in South Celtic Sea especially in proximity of bathymetric slope. The South Bay of Biscay is influenced by fully developed swell systems enhanced by refraction effects caused by both the coastline and bathymetry gradients. English Channel and North Sea show complex sea-states conditions induced by local topography features together with wind channelling and tide effects able to trigger geophysical processes at a sub-scale responsible for the development of multimodal seas. Crossing and bimodal seas are also found to be influenced by bathymetry gradients acting directly on the directional spectrum shape as well as by tide due to tidal current-induced refraction effect on wave propagation. No generalized significant trends are detected within the investigated spatial domain for the wave spectrum integral quantities; locations sited at northern Celtic Sea show a downward Significant Wave Height, while only locations confined at eastern English Chanel only shows a Peak Period upward trend.

Current induced effect on the resistivity in La0.8−xDyxNa0.2MnO3 monovalent doped manganites

The observation of electroresistance, ER effect in several substituted doped manganites which characterized the sensitivity of sample’s resistivity to the change of applied current was suggested can be enhanced by the presence of magnegtic inhomogenity. However, such effect is not well understood but the magnetic inhomogenity may influence the strength of ER related mechanism, hence current induced effect on the resistivity in monovalent doped La0.8−xDyxNa0.2MnO3 (x = 0.00–0.20) manganites prepared using solid state reaction method have been investigated to elucidate the matter. The ρ vs T curves shown that all samples exhibit smaller resistivity under higher applied current of 10 mA as compared to 5 mA of applied current in the wide temperature range of 30 K–300 K which led to ER effect. Measurement of ac susceptibility show that x = 0 sample exhibit ferromagnetic behaviour while both Dy substituted samples exhibit ferromagnetic to paramagnetic transition behavior with reduction in Tc values. Large ER effect with value of 130% at 300 K observed in ER vs. T curve for x = 0.1 sample, while for x = 0 the ER value is 9% indicates improved sensitivity of the Dy substituted sample towards electric field. While x = 0.20 sample exhibit double ER peaks which may related to presence of impurity phases. It is suggested Dy substitution induces magnetic inhomogeneities which favors formation of more filamentary conductive paths under the presence of high applied current thus enhanced the conduction process of charge carriers. The finding on the enhancement of ER effect indicates that the Dy substituted sample as potential candidates for spintronic-based devices.

Spin and orbital Hall currents detected via current-induced magneto-optical Kerr effect in V and Pt

Spin and orbital Hall currents detected via current-induced magneto-optical Kerr effect in V and Pt

Effects of Bi substitution on electroresistance behaviours in La0.8-xBixNa0.2MnO3 manganites

The observation of the electroresistance (ER) effect related to the reduction of resistivity under increased applied current indicates the potential of manganite material for next-generation spintronic-based devices. The observed behaviour was attributed to the presence of magnetic inhomogeneity. However, such relation is still not well understood, hence the current-induced effect on the resistivity in monovalent-doped La0.8-xBixNa0.2MnO3 (x = 0–0.20) manganite prepared via solid-state method is reported. All samples exhibited low resistivity in the temperature ranges of 30 K–300 K under a higher applied current of 5 mA compared with 1 mA, leading to the observation of the ER effect. The reduction of resistivity in the metallic region was due to the enhancement of DE itinerant hopping and the decrease in the scattering effect of conduction electrons, whereas in the insulating region, resistivity reduction is suggested to be related to the weakening of the electron–lattice attraction, as indicated by the reduction in activation energy (Ea) of charge carriers. Both x = 0.15 and x = 0.20 samples respectively exhibited large ER effects of 158% and 171% at 300 K amongst the studied samples. The enhancement of ER with Bi substitution is suggested due to the presence of magnetic inhomogeneities induced by MnO6 distortion which favours the formation of filamentary conduction paths under the presence of high applied current. The findings indicate that Bi substitution in La0.8-xBixNa0.2MnO3 (x = 0–0.20) manganites enhanced the sensitivity to the changes in electric field which shows that the investigated samples could be potentially used for non-volatile memory devices.

Third harmonic characterization of antiferromagnetic heterostructures

Electrical switching of antiferromagnets is an exciting recent development in spintronics, which promises active antiferromagnetic devices with high speed and low energy cost. In this emerging field, there is an active debate about the mechanisms of current-driven switching of antiferromagnets. For heavy-metal/ferromagnet systems, harmonic characterization is a powerful tool to quantify current-induced spin-orbit torques and spin Seebeck effect and elucidate current-induced switching. However, harmonic measurement of spin-orbit torques has never been verified in antiferromagnetic heterostructures. Here, we report harmonic measurements in Pt/α-Fe2O3 bilayers, which are explained by our modeling of higher-order harmonic voltages. As compared with ferromagnetic heterostructures where all current-induced effects appear in the second harmonic signals, the damping-like torque and thermally-induced magnetoelastic effect contributions in Pt/α-Fe2O3 emerge in the third harmonic voltage. Our results provide a new path to probe the current-induced magnetization dynamics in antiferromagnets, promoting the application of antiferromagnetic spintronic devices.

Electrically Controlled Wavelength-Tunable Photoluminescence from van der Waals Heterostructures.

Achieving facile control of the wavelength of light emitters is of great significance for many key applications in optoelectronics and photonics, including on-chip interconnection, super-resolution imaging, and optical communication. The Joule heating effect caused by electric current is widely applied in modulating the refractive index of silicon-based waveguides for reconfigurable nanophotonic circuits. Here, by utilizing localized Joule heating in the biased graphene device, we demonstrate electrically controlled wavelength-tunable photoluminescence (PL) from vertical van der Waals heterostructures combined by graphene and two-dimensional transition metal dichalcogenides (2D-TMDCs). By applying a moderate electric field of 6.5 kV·cm-1 to the graphene substrate, the PL wavelength of 2D-TMDCs exhibits a continuous tuning from 662 to 690 nm, corresponding to a bandgap reduction of 76 meV. The electric control is highly reversible during sweeping the bias back and forth. The temperature dependence of Raman and PL spectroscopy reveals that the current-induced local Joule heating effect plays a leading role in reducing the optical direct bandgap of TMDCs. The bias-dependent optical reflectivity and time-resolved photoluminescence measurements show a consistent reduction of the optical band gap of 2D-TMDCs and increased PL lifetimes with the electric field over the heterostructures. Moreover, we demonstrate the consistent device operation from 2D materials grown by chemical vapor deposition, showing great advantages for the scalability.

Superconducting orbital magnetoelectric effect and its evolution across the superconductor-normal metal phase transition

Superconducting magnetoelectric effect, which is the current-induced magnetization in a superconductor, mainly focused on the spin magnetization in previous studies, but ignore the effect of the orbital magnetic moments carried by the paired Bloch electrons. In this work, we show that orbital magnetic moments in superconductors can induce large orbital magnetization in the presence of a current. We constructed a unified description for the current-induced spin and orbital magnetization across the superconductivity normal metal phase transition. We find that in a superconductor with uniform pairing, the current-induced magnetization at a given current density is the same as that in its normal metal state, while with the nonuniform superconducting pairing, the current-induced magnetization exhibits an abrupt change in magnitude near the superconductivity normal metal phase transition. Importantly, our theory predicts the orbital magnetoelectric effect in superconducting twisted bilayer graphene which has paired Bloch electrons with large orbital magnetic moments and negligible spin-orbit coupling. We propose that the measurement of the current-induced orbital magnetoelectric effect can be used to detect the possible nonuniform pairings in twisted bilayer graphene and other newly discovered superconductors with non-trivial Berry curvatures.

A comparative study on the electrical and tribological characteristic of magnetron sputtered Ag, Cu and Al films under current-carrying friction

Purpose The purpose of this paper is to compare the electrical conductivity and tribological properties of magnetron sputtered silver (Ag), copper (Cu) and aluminum (Al) thin films under conductive grease lubrication. Design/methodology/approach Three types of silver (Ag), copper (Cu) and aluminum (Al) thin films were prepared by magnetron sputtering. Current-carrying friction tests were carried out by a ball-on-plate reciprocating friction and wear tester. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) were used to observe and analyze the worn surface and cross-section morphology of the films. Findings Silver and Cu films exhibited good conductivity and tribological properties, which were mainly attributed to the synergy of the protective tribofilm generated by conductive grease, current-induced thermal effect and magnetron sputtered films effect. Al film was worn through. Large pitting storing lubricate were only found in Ag film. Cu film showed a similar surface uniformity with Ag film. Originality/value This study provides a reference for the design and application of conductive grease and investigates the current-carrying friction behaviors of magnetron sputtered films as electrical contact materials. The comparison of current-carrying friction behaviors of the three films was rarely covered in previous studies.

Current-induced magnetization caused by crystal chirality in nonmagnetic elemental tellurium

Chiral matter has a structure that lacks inversion, mirror, and rotoreflection symmetry; thus, a given chiral material has either a right- or left-handed structure. In chiral matter, electricity and magnetism can be coupled in an exotic manner beyond the classical electromagnetism (e.g., magneto chiral effect in chiral magnets). In this paper, we give a firm experimental proof of the linear electric-current-induced magnetization effect in bulk nonmagnetic chiral matter elemental trigonal tellurium. We measured a Te125 nuclear magnetic resonance (NMR) spectral shift under a pulsed electric current for trigonal tellurium single crystals. We provide general symmetry considerations to discuss the electrically (electric-field- and electric-current-) induced magnetization and clarify that the NMR shift observed in trigonal tellurium is caused by the linear current-induced magnetization effect, not by a higher-order magnetoelectric effect. We also show that the current-induced NMR shift is reversed by a chirality reversal of the tellurium crystal structure. This result is direct evidence of crystal-chirality-induced spin polarization, which is an inorganic-bulk-crystal analog of the chirality-induced spin selectivity in chiral organic molecules. The present findings also show that nonmagnetic chiral crystals may be applied to spintronics and coil-free devices to generate magnetization beyond the classical electromagnetism.3 MoreReceived 20 October 2020Accepted 14 April 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023111Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasChiralityMagnetismMagnetoelectric effectSpin-orbit couplingSpintronicsPhysical SystemsElemental semiconductorsNarrow band gap systemsNoncentrosymmetric materialsTechniquesNuclear magnetic resonanceCondensed Matter, Materials & Applied Physics

Body Contact된 High Resistivity PD-SOI N-MOSFET에서 발생하는 RF Inductive 효과의 드레인 전압 종속성 분석

Gate 종횡비가 매우 큰 body contact(BCT) high resistivity(HR) partially depleted(PD) silicon-on-insulator(SOI) nMOSFET에서 발생되는 substrate current-induced body effect (SCBE)에 의해 고주파 SSUB21/SUB과 SSUB22/SUB -parameter에 생기는 RF inductive 효과의 전압 종속 특성을 SCBE 등가회로의 주파수 종속 어드미턴스 방정식을 사용하여 물리적으로 분석하였다. 출력 negative 캐패시턴스를 시뮬레이션할 수 있는 복잡한 SCBE 모델 대신에 간단한 RLC 병렬 공진 회로로 RF inductive 효과를 모델한 후 소신호 등가회로를 사용하여 SCBE 저항, 인덕턴스와 공진주파수의 드레인 전압 종속 특성을 추출하고 검증하였다.

Current-induced phonon Hall effect

Since the first experimental observation of the phonon Hall effect (PHE) in 2005, its physical origin and theoretical explanation have been extensively investigated. While spin-orbit interactions are believed to play important roles under external magnetic fields, nonmagnetic effects are also possible. Here, we propose a mechanism of PHE which is induced by electric current in a nonequilibrium system through electron-phonon interactions. The influence of the drift electrons to the phonon degrees of freedom, as a correction to the Born-Oppenheimer approximation, is represented by an antisymmetric matrix which has the same form as in a typical phonon Hall model. We demonstrate the idea with a graphene-like hexagonal lattice having a finite phonon Hall conductivity under a driven electric current.

Analysis of RF Inductive Effect in S-Parameters of Body Contact PD-SOI MOSFETs

The anomalous RF inductive effect in which ${S}_{{21}}$ - and ${S}_{{22}}$ -parameters rotate clockwise in the lower and upper half-circles, respectively, with increasing the frequency at the high ${V}_{\text {DS}}$ region has been investigated in body contact (BCT) high-resistivity (HR) partially depleted (PD) silicon-on-insulator (SOI) nMOSFETs with a very high aspect ratio of gate finger. The negative output capacitance generated from a substrate current-induced body effect (SCBE) is physically identified for the first time as the origin of the RF inductive effect by deriving the output admittance equation of a body transconductance source in RF equivalent circuit model considering SCBE. The bias-dependent frequency effect that the drain–source conductance and negative capacitance converted from measured ${S}$ -parameters are largely reduced by higher pole frequency with increasing ${V}_{\text {DS}}$ is clearly explained by admittance equations derived from the SCBE output equivalent circuit. The bias-dependencies of inductive effect parameters related to SCBE are accurately extracted using small-signal equivalent circuit modeling of BCT PD-SOI nMOSFETs. Based on this result, the bias-dependence of ${S}_{{21}}$ - and ${S}_{{22}}$ -parameters is analyzed in detail.

Thermally Assisted Skyrmion Memory (TA-SKM)

A novel thermally assisted skyrmion memory (TA-SKM) has been proposed and studied for the first time. Unidirectional current-induced spin transfer torque (STT) and Joule heating effect are used to induce the magnetization switching between uniform and skyrmion states in the free layer of a magnetic tunnel junction device. Physics-based simulations suggest that TA-SKM offers advantages including unipolar switching feature for cross-point memory integration, better TMR design as compared to STT-MRAM, and improved operation temperature range as compared to TA-MRAM.

Quantitative Study on Current-Induced Effect in an Antiferromagnet Insulator/Pt Bilayer Film.

A quantitative investigation of the current-induced torque in antiferromagnets represents a great challenge due to the lack of an independent method for controlling Néel vectors. By utilizing an antiferromagnetic insulator with the Dzyaloshinskii-Moriya interaction α-Fe_{2}O_{3}, we show that the Néel vector can be controlled with a moderate external field, which is further utilized to calibrate the current-induced magnetic dynamics. We find that the current-induced magnetoresistance change in antiferromagnets can be complicated by resistive switching that does not have a magnetic origin. By excluding nonmagnetic switching and comparing the current-induced dynamics with the field-induced one, we determine the nature and magnitude of current-induced effects in Pt/α-Fe_{2}O_{3} bilayer films.

Negative differential resistance and quantum oscillations in FeSb2 with embedded antimony**Project supported by Guangdong Innovative and Entrepreneurial Research Team Program, China (Grant No. 2016ZT06D348), the National Natural Science Foundation of China (Grant No. 11874193), and the Shenzhen Fundamental Subject Research Program, China (Grant Nos. JCYJ20170817110751776 and JCYJ20170307105434022). The work at Brookhaven is supported by the US Department of Energy, Office

We present a systematical study on single crystalline FeSb2 using electrical transport and magnetic torque measurements at low temperatures. Nonlinear magnetic field dependence of Hall resistivity demonstrates a multi-carrier transport instinct of the electronic transport. Current-controlled negative differential resistance (CC-NDR) observed in current–voltage characteristics below ∼ 7 K is closely associated with the intrinsic transition ∼ 5 K of FeSb2, which is, however, mediated by extrinsic current-induced Joule heating effect. The antimony crystallized in a preferred orientation within the FeSb2 lattice in the high-temperature synthesis process leaves its fingerprint in the de Haas-Van Alphen (dHvA) oscillations, and results in the regular angular dependence of the oscillating frequencies. Nevertheless, possible existence of intrinsic non-trivial states cannot be completely ruled out. Our findings call for further theoretical and experimental studies to explore novel physics on flux-free grown FeSb2 crystals.

Apparent delocalization of the current density in metallic wires observed with diamond nitrogen-vacancy magnetometry

We report on a quantitative analysis of the magnetic field generated by a continuous current running in metallic microwires fabricated on an electrically insulating diamond substrate. A layer of nitrogen-vacancy (NV) centers engineered near the diamond surface is employed to obtain spatial maps of the vector magnetic field, by measuring Zeeman shifts through optically detected magnetic resonance spectroscopy. The in-plane magnetic field (i.e., parallel to the diamond surface) is found to be significantly weaker than predicted, while the out-of-plane field also exhibits an unexpected modulation. We show that the measured magnetic field is incompatible with Amp\`ere's circuital law or Gauss's law for magnetism when we assume that the current is confined to the metal, independent of the details of the current density. This result was reproduced in several diamond samples, with a measured deviation from Amp\`ere's law by as much as 94(6)% (i.e., a $15\ensuremath{\sigma}$ violation). To resolve this apparent magnetic anomaly, we introduce a generalized description whereby the current is allowed to flow both above the NV sensing layer (including in the metallic wire) and below the NV layer (i.e., in the diamond). Inversion of the Biot-Savart law within this two-channel description leads to a unique solution for the two current densities that completely explains the data, is consistent with the laws of classical electrodynamics, and indicates a total NV-measured current that closely matches the electrically measured current. However, this description also leads to the surprising conclusion that in certain circumstances the majority of the current appears to flow in the diamond substrate rather than in the metallic wire, and to spread laterally in the diamond by several micrometers away from the wire. No electrical conduction was observed between nearby test wires, ruling out a conventional conductivity effect. Moreover, the apparent delocalization of the current into the diamond persists when an insulating layer is inserted between the metallic wire and the diamond or when the metallic wire is replaced by a graphene ribbon. The possibilities of a measurement error, a problem in the data analysis, or a current-induced magnetization effect are discussed, but do not seem to offer a more plausible explanation for the effect. Understanding and mitigating this apparent anomaly will be crucial for future applications of NV magnetometry to charge transport studies.

Field Characteristics of Spin-Torque Diode Sensitivity in the Presence of a Bias Current

The use of the spin-torque diode effect, which is generated upon the current-induced transfer of spin angular momentum in magnetic tunnel junctions, opens the prospect of considerably improving microwave sensitivity in the gigahertz frequency band over that of semiconductor Schottky diodes. In this work, the spin-diode effect of microwave signal rectification in a magnetic tunnel junction upon the resonant excitation of spin waves in the free magnetic layer as a result of the current-induced spin-transfer torque effect is analyzed theoretically. Frequency characteristics of the resonant response of a spin-torque diode to a microwave signal are calculated in the linear macrospin approximation as functions of the direction and value of the applied magnetic field and bias current. It is shown that with zero bias current, the maximum rectified voltage across a junction is obtained in the geometry of mutually perpendicular magnetizations of magnetic layers; as the resonant frequency of oscillations in a magnetic field increases, this voltage drops at the retained equilibrium orientation of spins in the layers. After the bias current is switched on, the resonance amplitude of forced oscillations of the free layer spins upon microwave excitation grows sharply at the critical point of the spin-torque diode’s loss of equilibrium state stability. The linewidth at this point is limited only by nonlinear effects. Improving spin-torque diode sensitivity is important for its use in microwave holographic vision systems.