Polarization Switching Research Articles

Electrical mutual switching in a noncollinear-antiferromagnetic–ferromagnetic heterostructure

Spin-orbit torque (SOT) provides a promising mechanism for electrically encoding information in magnetic states. Unlike existing schemes, where the SOT is passively determined by the material and device structures, an active manipulation of the intrinsic SOT polarity would allow for flexibly programmable SOT devices. Achieving this requires electrical control of the current-induced spin polarization of the spin source. Here we demonstrate a proof-of-concept current-programmed SOT device. Using a noncollinear-antiferromagnetic/nonmagnetic/ferromagnetic Mn3Sn/Mo/CoFeB heterostructure at zero magnetic field, we show current-induced switching in the CoFeB layer due to the spin current polarized by the magnetic structure of the Mn3Sn; by properly tuning the driving current, the spin current from the CoFeB further reverses the magnetic orientation of the Mn3Sn, which determines the polarity of the subsequent switching of the CoFeB. This scheme of mutual switching can be achieved in a spin-valve-like simple protocol because each magnetic layer serves as a reversible spin source and target magnetic electrode. It yields intriguing proof-of-concept functionalities for unconventional logic and neuromorphic computing.

Development and Validation of Targeted Metabolomics Methods Using Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS) for the Quantification of 235 Plasma Metabolites

Plasma contains metabolites with diverse physicochemical properties, ranging from highly polar to highly apolar, and concentrations spanning at least nine orders of magnitude. Plasma metabolome analysis is valuable for monitoring health and evaluating medical interventions but is challenging due to the metabolome’s diversity and complexity. This study aims to develop and validate targeted LC-MS/MS methods for quantifying 235 mammalian metabolites from 17 compound classes in porcine plasma without prior derivatization. Utilizing reversed-phase and hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry, each analyte is identified and quantified using two selected reaction monitoring (SRM) transitions. Fast polarity switching and scheduled SRM enhance the metabolome coverage and throughput, enabling the analysis of one sample in about 40 min. A simple “dilute and shoot” sample preparation protocol was employed, with samples injected at two dilution levels to align metabolite concentrations within calibration curve ranges. Validation in porcine plasma included assessments of carryover, linearity, detection and quantification limits, repeatability and recovery. The method was further applied to plasma samples from various animal species, demonstrating its applicability to human and animal studies. This study establishes two robust LC-MS/MS methods for comprehensive porcine plasma metabolome quantification, advancing large-scale targeted metabolomics in biomedical research.

Unipolar polarization switching and high-endurance memory operation of HZO/Si anti-ferroelectric FETs

Abstract We experimentally demonstrate the anti-ferroelectric (AFE) behavior of a Hf1-xZrxO2 (HZO)/Si FET and its potential for high-endurance nonvolatile memory operation. The AFE-HZO FET with Zr content of 75 % exhibits a double polarization switching and half-loop switching of its double hysteresis under bipolar and unipolar bias conditions, respectively. The counterclockwise hysteresis in the transfer Id -Vg characteristics is demonstrated under unipolar Vg sweep through half-loop polarization in AFeFET. The steep subthreshold swing values were observed for both forward and backward Vg sweeps of Id -Vg curves for AFeFET under unipolar bias condition. The nonvolatile feature of AFeFET is achieved by introducing the optimized hold voltage of 1.3 V during the retention period. The threshold voltage shift can be realized by utilizing the unipolar program /erase Vg pulses. Also, the high-endurance properties of HZO/Si AFeFET are demonstrated under unipolar Vg stress with observable memory window up to 109 cycles without gate insulator breakdown.

Resolving polarization switching pathways of sliding ferroelectricity in trilayer 3R-MoS2.

Sliding ferroelectricity, an emerging type of hysteretic behaviour with strong potential for memory-related applications, involves dynamically switching the polarization associated with the stacking arrangement in two-dimensional van der Waals materials. Because different stacking configurations can share a degenerate net polarization, it has remained a challenge to resolve the intermediate stacking configuration and the polarization switching pathway in multi-interface devices. In this work, we present an optical approach to resolve the polarization degeneracy in a trilayer 3R-MoS2 over different switching cycles. By performing reflection contrast spectroscopy in dual-gated devices, we identify distinct responses of inter- and intralayer excitons in all four possible stacking configurations (ABC, ABA, BAB and CBA). Diffraction-limited spatial resolution makes it possible to image the switching of the stacking configurations. We find that the switching pathway is influenced not only by the competition among pinning centres-which localize domain walls at different interfaces-but also by a free-carrier screening effect linked to chemical doping. These findings highlight the importance of managing domain walls, pinning centres and doping levels in sliding ferroelectric devices, offering insights for further development in sensing and computing applications.

High-throughput UPLC-ESI/MSMS method for simultaneous measurement of the urinary metabolites of volatile organic compounds and tobacco alkaloids.

Human exposure to volatile organic compounds (VOCs) poses significant health risks, contributing to cardiovascular disease, pulmonary disease, and cancer. Measurement of VOC metabolites (VOCm) in urine by liquid chromatography-mass spectrometry (LC-MS) is a preferred method for VOCm analysis; however, existing methods encounter challenges related to sensitivity, throughput, and analyte coverage. In addition to VOCm, the measurement of tobacco alkaloids (TAm) is critical to account for tobacco use in population-based studies. A method is needed that is highly sensitive, offers higher throughput, and can analyze VOCm and TAm in a single run. Herein, we present a robust dilute-and-shoot method aimed at overcoming these analytical challenges and expanding the targeted analysis to include 35 urinary VOCm and TAm and their metabolites. By leveraging high-speed polarity switching and optimized chromatographic parameters, our method achieved comprehensive analyte coverage and enhanced sensitivity, enabling reliable individual level VOC exposure assessment. Validation demonstrates robust linearity, sensitivity, accuracy, and precision, with minimal matrix effects. This high-throughput UPLC-MS/MS method significantly enhances VOC exposure assessment by enabling simultaneous measurement of 35 urinary VOC and TAm with high sensitivity and efficiency. Multiple metabolites from single parent xenobiotics are included in one run, expanding biomarker specificity. Our data indicate the method effectively accounts for tobacco consumption as a confounder in population-based studies, ensuring accurate VOC exposure assessment.

Polarization Switching from Valence Trapping in an Oxo-Bridged Trinuclear Iron Complex.

Switching electric polarization by external stimuli constitutes a technical foundation for various applications. Here, we reported the observation of polarization-switching behavior in an oxo-bridged mixed-valence complex [Fe3O(piv)6(py)3] (piv = pivalate, py = pyridine). Detailed variable-temperature Mössbauer spectral analyses unambiguously confirm the occurrence of an electron localization-delocalization transition between two inequivalent Fe sites. Given that the compound crystallizes in a polar space group, the change in the molecular dipole moments leads to a pyroelectric effect observed during this transition, indicating thermally induced polarization switching behavior. As the complex exhibits asymmetry in the valence-active sites and antiferromagnetic interaction between them, the possibility of magnetoelectric coupling in this compound is also discussed on the basis of the recent prediction of polarization switching through modulating the degree of electron delocalization by magnetic fields in the mixed-valence systems.

Defective ground structure loaded polarization reconfigurable ring-shaped patch antenna for multiband applications

ABSTRACT A novel stub-loaded polarization-reconfigurable ring-shaped circular patch antenna designed for multi-band operation and switchable polarization is presented, having advantages such as ease in manufacturing and compact size (20 mm × 20 mm). The circular ring is segmented into four sectors, and two stubs are loaded on the inner side of the ring to disrupt the current distribution and create two orthogonal electric field vectors, generating circular polarization. The antenna supports it in switching three distinct polarization states: linear polarization, left-hand circular polarization, and right-hand circular polarization, selectable with different combinations of diodes. From the measured results, ARBW (<3 dB) is 32.12% and 6.06% for CP bands. Additionally, eight LP bands with IBW of 71.66%, 3.55%, 3.94%, 35.88%, 45%, 45.5%, 34.77%, and 8.2% are achieved. The antenna exhibits satisfactory stable gain across all frequency bands and excellent radiation performance, making it a promising candidate for modern wireless communication applications (C-band, ITS2 fixed, X-band, and Ku-band satellite downlink operations).

Electrochemical Denitrative Cyclization Driven by Alternating Polarity.

Alternating current electrolysis has emerged as a promising technique for addressing challenging redox reactions that are otherwise difficult or impossible for direct current electrolysis. Under mild and transition-metal-free reaction conditions, a general electrochemical denitrative cyclization of nitroarenes was developed to access various cyclic sulfone-containing derivatives of biological significance. The key to success lies in the facile manipulation of multiple redox events upon rapid alternating polarity switching to enhance the selectivity and efficiency.

Lowering the coercive field of van der Waals ferroelectric NbOI2 with photoexcitation

Polarization switching in van der Waals ferroelectric materials driven by an electric field remains robust even at the atomic layer limit, paving the way for advances in the miniaturization and integration of ferroelectric devices. Thus, understanding the modulation of ferroelectric properties in two-dimensional ferroelectric materials is essential for their efficient nanoscale applications. NbOI2, a recently confirmed van der Waals ferroelectric, offers an ideal platform for investigating in-plane spontaneous polarization at the nanoscale. We explored the influence of laser excitation on the ferroelectric polarization properties of NbOI2. In multilayer NbOI2 devices with in-plane configurations, no significant current signals were detected along the c-axis or b-axis (the ferroelectric polarization axis) in the absence of illumination. However, under laser excitation, the material exhibited clear hysteresis loop behavior along both the c-axis and b-axis, indicating that laser excitation effectively reduces the coercive voltage. Furthermore, at the same excitation wavelength, the current peak along the c-axis was larger, with more pronounced hysteresis loops. Our experimental findings demonstrate that laser excitation can lower the coercive field in multilayer NbOI2 and induce different electrical hysteresis behavior along different crystallographic orientations, providing valuable insights for the development of NbOI2-based optoelectronic devices.

Reward based optimization of resonance-enhanced piezoresponse spectroscopy

Dynamic spectroscopies in scanning probe microscopy (SPM) are critical for probing material properties, such as force interactions, mechanical properties, polarization switching, electrochemical reactions, and ionic dynamics. However, the practical implementation of these measurements is constrained by the need to balance imaging time and data quality. Signal to noise requirements favor long acquisition times and high frequencies to improve signal fidelity. However, these are limited on the low end by contact resonant frequency and photodiode sensitivity and on the high end by the time needed to acquire high-resolution spectra or the propensity for sample degradation under high field excitation over long times. The interdependence of key parameters such as instrument settings, acquisition times, and sampling rates makes manual tuning labor-intensive and highly dependent on user expertise, often yielding operator-dependent results. These limitations are prominent in techniques like dual amplitude resonance tracking in piezoresponse force microscopy that utilize multiple concurrent feedback loops for topography and resonance frequency tracking. Here, a reward-driven workflow is proposed that automates the tuning process, adapting experimental conditions in real time to optimize data quality. This approach significantly reduces the complexity and time required for manual adjustments and can be extended to other SPM spectroscopic methods, enhancing overall efficiency and reproducibility.

Correlation between ferroelectricity and torsional motion of acetyl groups in tris(4-acetylphenyl)amine observed by muon spin relaxation

It is demonstrated by muon spin relaxation and resonance experiments that the switchable spontaneous polarization of the organic ferroelectric compound tris(4-acetylphenyl)amine is governed by the local molecular dynamics of the acetyl group. The implanted muon forms paramagnetic states, which exhibit longitudinal spin relaxation due to the fluctuation of hyperfine fields exerted from unpaired electrons. The first-principle density functional theory calculations indicate that these states are muonated radicals localized at the phenyl group and on the carbon/oxygen of the acetyl group, thereby suggesting that the spin relaxation is dominated by the random torsional motion of an acetyl group around the C–C bond to the phenyl group. The stepwise change in the relative yield of radicals at T0≈350 K and the gradual increase in the spin relaxation rate with temperature (T) indicate that the torsional motion is significantly enhanced by thermal excitation above T0. This occurs concomitantly with the strong enhancement in the atomic displacement parameter of oxygen in the acetyl group (which is non-linear in T), indicating that it is the local molecular motion of the acetyl groups that drives the structural transition.

Cross-Point Ferroelectric Hf0.5Zr0.5O2 Capacitors for Remanent Polarization-Driven In-Memory Computing.

Ferroelectric Hf0.5Zr0.5O2 (HZO) capacitors have been extensively explored for in-memory computing (IMC) applications due to their nonvolatility and back-end-of-line (BEOL) compatible process. Several IMC approaches using resistance and capacitance states in ferroelectric HZO have been proposed for vector-matrix multiplication (VMM), but previous approaches suffer from limited accuracy and reliability. In this work, we propose a promising approach centered on the remanent polarization (Pr) switching of binary ferroelectric HZO capacitor synapses. We experimentally demonstrate a simple pattern recognition task showing that the voltage readout of Pr switching provides excellent accuracy due to its high on/off ratio and consequent reliability. We also performed large-scale simulations on a complex inference task, achieving high accuracy and immunity to device variations. We therefore believe that our proposed paradigm is promising for near-term neuromorphic IMC.

Metallic Sliding Ferroelectricity in Trilayer Penta‐NiN2

AbstractThe experimental observation of metallic ferroelectricity has challenged the traditional understanding in recent years, as metallicity and ferroelectricity are historically considered mutually exclusive. This breakthrough has sparked significant interest in this field. However, the coexistence of metallicity and sliding ferroelectricity in 2D pentagonal materials has not been reported yet. Here, this is theoretically studied that the sliding ferroelectricity in metallic trilayer penta‐NiN2. By scanning the configuration space of stacking patterns, a pair of polarized configurations is identified with strong out‐of‐plane ferroelectric polarization of ± 5.39 × 10−13 C m−1 and a low polarization switching barrier of 14.33 meV/atom together with a non‐polarized configuration as the intermediate state for the ferroelectric transition. It is also found that there are substantial changes in the second harmonic generation of the stable configurations that would facilitate experimental observation. This work demonstrates the potential of pentagonal sheets as promising metallic sliding ferroelectrics, which would significantly expand the family of sliding ferroelectric materials.

Switchable Hydrophilicity Amine Product Extraction: Efficient Separation of Tertiary Amines via Carbon Dioxide-Induced Polarity Switch in Homogeneous Catalysis

Switchable Hydrophilicity Amine Product Extraction: Efficient Separation of Tertiary Amines via Carbon Dioxide-Induced Polarity Switch in Homogeneous Catalysis

2D Van der Waals Sliding Ferroelectrics Toward Novel Electronic Devices.

Ferroelectric materials, celebrated for their switchable polarization, have undergone significant evolution since their early discovery in Rochelle salt. Initial challenges, including water solubility and brittleness, are overcome with the development of perovskite ferroelectrics, which enable the creation of stable, high-quality thin films suitable for semiconductor applications. As the demand for miniaturization in nanoelectronics has increased, research has shifted toward low-dimensional materials. Traditional ferroelectrics often lose their properties at the nanoscale; however, 2D van der Waals (vdW) ferroelectrics, including CuInP2S6 and α-In2Se3, have emerged as promising alternatives. The recent discovery of sliding ferroelectricity, where polarization is linked to the polar stacking configuration of originally non-polar monolayers, has significantly broadened the scope of 2D ferroelectrics. This review offers a comprehensive examination of stacking orders in 2D vdW materials, stacking-order-linked ferroelectric polarization structures, and their manifestations in metallic, insulating and semiconducting 2D vdW materials. Additionally, it explores the applications of 2D vdW sliding ferroelectrics, and discusses the future prospects innanotechnology.

High spin-orbit torque efficiency induced by engineering spin absorption for fully electric-driven magnetization switching.

Realizing spin-orbit torque (SOT)-driven magnetization switching offers promising opportunities for the advancement of next-generation spintronics. However, the relatively low charge-spin conversion efficiency accompanied by an ultrahigh critical switching current density (Jc) remains a significant obstacle to the further development of SOT-based storage elements. Herein, spin absorption engineering at the ferromagnet/nonmagnet interface is firstly proposed to achieve high SOT efficiency in Pt/Co/Ir trilayers. The Jc value was significantly decreased to 7.5 × 106 A cm-2, achieving a maximum reduction of 58% when a 4.0-nm Gd layer was inserted into the Co/Ir interface. A similar trend was observed in the trilayers with various rare metal insertions, suggesting the universality of this approach. Simultaneously, the highest effective spin Hall angle of 0.29 was obtained in the Pt/Co/Gd (4.0 nm)/Ir multilayers, which was approximately three times greater than that obtained in the Pt/Co/Ir trilayer. First-principles calculations together with polarized neutron reflectivity results revealed that spin mixed conductivity can be significantly enhanced due to a spontaneous interfacial CoGd alloy, which is critical for high SOT efficiency. In addition, the deterministic field-free switching polarity can be tuned by introducing Gd insertion. These findings provide a promising pathway for deeply understanding the spin-charge conversion mechanism, and further enable the design of low-consumption spintronic circuits.

Unconventional Ferroelectric-Ferroelastic Switching Mediated by Non-Polar Phase in Fluorite Oxides.

HfO2/ZrO2-based ferroelectrics present tremendous potential for next-generation non-volatile memory due to their high scalability and compatibility with silicon technology. Unlike the continuous polar layers in perovskite ferroelectrics, HfO2/ZrO2-based ferroelectrics are composed of alternating polar layers with oxygen shifts and non-polar spacers, which leads to a distinct ferroelectric switching mechanism. However, directly observing the switching process has been a big challenge due to the polymorph feature of nanoscale fluorites and the difficulty in in situ imaging on light elements. Here, the ferroelectric-ferroelastic coupled switching process in freestanding ZrO2 thin films is directly visualized by in situ imaging on oxygen motions. A multi-step 90-degree polarization switching mechanism is uncovered that challenges the conventional one-step 180-degree switching paradigms in fluorite oxides, which is highly consistent with the interlocked nature of ferroelectricity and ferroelasticity. A non-polar tetragonal (T) phase is discovered as a crucial intermediate state, lowering the energy barrier for polarization switching by 35%. More importantly, the T phase prevents irreversible transitions to the non-polar ground state and facilitates stable ferroelectric switching. These findings are fundamental to understanding nanoscale polarization switching mechanisms in fluorite ferroelectrics, paving the way for advanced high-durability devices.

Novel Magnetic-Field-Free Switching Behavior in vdW-Magnet/Oxide Heterostructure.

Magnetization switching by charge current without a magnetic field is essential for device applications and information technology. It generally requires a current-induced out-of-plane spin polarization beyond the capability of conventional ferromagnet/heavy-metal systems, where the current-induced spin polarization aligns in-plane orthogonal to the in-plane charge current and out-of-plane spin current. Here, a new approach is demonstrated for magnetic-field-free switching by fabricating a van-der-Waals magnet and oxide Fe3GeTe2/SrTiO3 heterostructure. This new magnetic-field-free switching is possible because the current-driven accumulated spins at the Rashba interface precess around an emergent interface magnetism, eventually producing an ultimate out-of-plane spin polarization. This interpretation is further confirmed by the switching polarity change controlled by the in-plane initialization magnetic fields with clear hysteresis. Van-der-Waals magnet and oxide are successfully combined for the first time, especially taking advantage of spin-orbit torque on the SrTiO3 oxide. This allows this study to establish a new way of magnetic field-free switching. This work demonstrates an unusual perpendicular switching application of large spin Hall angle materials and precession of accumulated spins, and in doing so, opens up a new field and opportunities for van-der-Waals magnets and oxide spintronics.

Data-Driven Discovery of High-Performance Heterobilayer Transition Metal Dichalcogenide-Based Sliding Ferroelectrics.

The development of efficient sliding ferroelectric (FE) materials is crucial for advancing next-generation low-power nanodevices. Currently, most efforts focus on homobilayer two-dimensional materials, except for the experimentally reported heterobilayer sliding FE, MoS2/WS2. Here, we first screened 870 transition metal dichalcogenide (TMD) bilayer heterostructures derived from experimentally characterized monolayer TMDs and systematically investigated their sliding ferroelectric behavior across various stacking configurations using high-throughput calculations. On the basis of the generated data, we developed an efficient descriptor, named the amplitude of Allen electronegativity difference (Δχm), for identifying van der Waals heterobilayers with sliding FE properties. Finally, 16 semiconducting TMD heterobilayers are identified as exhibiting interlayer sliding FE alongside low switching barriers (<21 meV/f.u.), with 10 outperforming the experimental MoS2/WS2 system, showing the largest out-of-plane polarization (OPP) values up to 10 times higher than MoS2/WS2. These materials exhibit favorable band gaps (0.60-1.80 eV) using the HSE06 method, making them suitable for sliding FE applications. Our findings reveal that polarization switching in these heterobilayers is strongly influenced by the interplay of stacking patterns, material electronegativity, charge transfer, and electronic structures. This study provides a robust framework for designing novel sliding ferroelectric materials and offers a theoretical basis for future experimental research.

Comprehensive untargeted polar metabolite analysis using solvent switching liquid chromatography tandem mass spectrometry.

Metabolomics analyses enable the examination and identification of endogenous biochemical reaction products, revealing information on the metabolic pathways and processes active within a living cell or organism. Determination of metabolic shifts can provide important information on a treatment or disease. Unlike other omics fields that typically have analytes of the same chemical class with common building blocks, those that fall under the nomenclature of metabolites encompass a wide array of different compounds with very diverse physiochemical properties. Development of a comprehensive metabolomic pipeline therefore can be a troublesome and complicated process for the analyst. Often single liquid chromatography-mass spectrometry methods on unfractionated samples are carried out in order to be time-efficient, however this could potentially produce data with a low number of identifiable metabolites. In the present studies, we developed a comprehensive polar metabolomics pipeline for cell-based metabolomics. SH-SY5Y neuroblastoma cells were selected as the sample matrix for method development since they are one of the most widely used cell lines for human neurotoxicity studies. This was accomplished by investigating and optimising different mass spectrometry source and chromatographic conditions to enhance the signal of polar metabolites. Optimised hydrophilic interaction liquid chromatography (HILIC) based metabolomic methods at different pH values were examined in positive, negative, and polarity switching modes to determine which combination yielded the highest number of confidently identified metabolites. Additionally, the use of sequentially running two methods was also compared to determine the degree of overlap and whether there is merit in running two separate methods on one sample. It was determined that solvent switching between two optimised methods, acidic chromatographic conditions in positive mode and basic chromatographic conditions in negative mode, yielded the highest number of unique identifiable metabolites. This could be run in a single analytical batch due to the large pH range of the column. A quick switch method in-between each method allowed both conditioning the column and preparation of the MS source conditions for the sequential method.