Octupole-driven magnetoresistance in an antiferromagnetic tunnel junction.

The tunnelling electric current passing through a magnetic tunnel junction (MTJ) is strongly dependent on the relative orientation of magnetizations in ferromagnetic electrodes sandwiching an insulating barrier, rendering efficient readout of spintronics devices1-5. Thus, tunnelling magnetoresistance (TMR) is considered to be proportional to spin polarization at the interface1 and, to date, has been studied primarily in ferromagnets. Here we report observation of TMR in an all-antiferromagnetic tunnel junction consisting of Mn3Sn/MgO/Mn3Sn (ref. 6). We measured a TMR ratio of around 2% at room temperature, which arises between the parallel and antiparallel configurations of the cluster magnetic octupoles in the chiral antiferromagnetic state. Moreover, we carried out measurements using a Fe/MgO/Mn3Sn MTJ and show that the sign and direction of anisotropic longitudinal spin-polarized current in the antiferromagnet7 can be controlled by octupole direction. Strikingly, the TMR ratio (about 2%) of the all-antiferromagnetic MTJ is much larger than that estimated using the observed spin polarization. Theoretically, we found that the chiral antiferromagnetic MTJ may produce a substantially large TMR ratio as a result of the time-reversal, symmetry-breaking polarization characteristic of cluster magnetic octupoles. Our work lays the foundation for the development of ultrafast and efficient spintronic devices using antiferromagnets8-10.

Perpendicular full switching of chiral antiferromagnetic order by current.

Electrical control of a magnetic state of matter lays the foundation for information technologies and for understanding of spintronic phenomena. Spin-orbit torque provides an efficient mechanism for the electrical manipulation of magnetic orders1-11. In particular, spin-orbit torque switching of perpendicular magnetization in nanoscale ferromagnetic bits has enabled the development of stable, reliable and low-power memories and computation12-14. Likewise, for antiferromagnetic spintronics, electrical bidirectional switching of an antiferromagnetic order in a perpendicular geometry may have huge impacts, given its potential advantage for high-density integration and ultrafast operation15,16. Here we report the experimental realization of perpendicular and full spin-orbit torque switching of an antiferromagnetic binary state. We use the chiral antiferromagnet Mn3Sn (ref. 17), which exhibits the magnetization-free anomalous Hall effect owing to a ferroic order of a cluster magnetic octupole hosted in its chiral antiferromagnetic state18. We fabricate heavy-metal/Mn3Sn heterostructures by molecular beam epitaxy and introduce perpendicular magnetic anisotropy of the octupole using an epitaxial in-plane tensile strain. By using the anomalous Hall effect as the readout, we demonstrate 100 per cent switching of the perpendicular octupole polarization in a 30-nanometre-thick Mn3Sn film with a small critical current density of less than 15 megaamperes per square centimetre. Our theory reveals that the perpendicular geometry between the polarization directions of current-induced spin accumulation and of the octupole persistently maximizes the spin-orbit torque efficiency during the deterministic bidirectional switching process. Our work provides a significant basis for antiferromagnetic spintronics.

Clamping enables enhanced electromechanical responses in antiferroelectric thin films.

Thin-film materials with large electromechanical responses are fundamental enablers of next-generation micro-/nano-electromechanical applications. Conventional electromechanical materials (for example, ferroelectrics and relaxors), however, exhibit severely degraded responses when scaled down to submicrometre-thick films due to substrate constraints (clamping). This limitation is overcome, and substantial electromechanical responses in antiferroelectric thin films are achieved through an unconventional coupling of the field-induced antiferroelectric-to-ferroelectric phase transition and the substrate constraints. A detilting of the oxygen octahedra and lattice-volume expansion in all dimensions are observed commensurate with the phase transition using operando electron microscopy, such that the in-plane clamping further enhances the out-of-plane expansion, as rationalized using first-principles calculations. In turn, a non-traditional thickness scaling is realized wherein an electromechanical strain (1.7%) is produced from a model antiferroelectric PbZrO3 film that is just 100 nm thick. The high performance and understanding of the mechanism provide a promising pathway to develop high-performance micro-/nano-electromechanical systems.

Manipulating chiral spin transport with ferroelectric polarization.

A magnon is a collective excitation of the spin structure in a magnetic insulator and can transmit spin angular momentum with negligible dissipation. This quantum of a spin wave has always been manipulated through magnetic dipoles (that is, by breaking time-reversal symmetry). Here we report the experimental observation of chiral spin transport in multiferroic BiFeO3 and its control by reversing the ferroelectric polarization (that is, by breaking spatial inversion symmetry). The ferroelectrically controlled magnons show up to 18% modulation at room temperature. The spin torque that the magnons in BiFeO3 carry can be used to efficiently switch the magnetization of adjacent magnets, with a spin-torque efficiency comparable to the spin Hall effect in heavy metals. Utilizing such controllable magnon generation and transmission in BiFeO3, an all-oxide, energy-scalable logic is demonstrated composed of spin-orbit injection, detection and magnetoelectric control. Our observations open a new chapter of multiferroic magnons and pave another path towards low-dissipation nanoelectronics.

Observation of the antiferromagnetic spin Hall effect.

The discovery of the spin Hall effect1 enabled the efficient generation and manipulation of the spin current. More recently, the magnetic spin Hall effect2,3 was observed in non-collinear antiferromagnets, where the spin conservation is broken due to the non-collinear spin configuration. This provides a unique opportunity to control the spin current and relevant device performance with controllable magnetization. Here, we report a magnetic spin Hall effect in a collinear antiferromagnet, Mn2Au. The spin currents are generated at two spin sublattices with broken spatial symmetry, and the antiparallel antiferromagnetic moments play an important role. Therefore, we term this effect the 'antiferromagnetic spin Hall effect'. The out-of-plane spins from the antiferromagnetic spin Hall effect are favourable for the efficient switching of perpendicular magnetized devices, which is required for high-density applications. The antiferromagnetic spin Hall effect adds another twist to the atomic-level control of spin currents via the antiferromagnetic spin structure.

Tumor Deposits and Perineural Invasion had Comparable Impacts on the Survival of Patients With Non-metastatic Colorectal Adenocarcinoma: A Population-Based Propensity Score Matching and Competing Risk Analysis.

BACKGROUND: Both tumor deposits (TD) and perineural invasion (PNI) have been identified as risk factors for poor survival in patients with non-metastatic colorectal adenocarcinoma (CRC). However, the adverse impacts of TD and PNI on the survival of patients with non-metastatic CRC have not been compared. METHOD: Patients with non-metastatic CRC with known TD and PNI status were selected from the Surveillance, Epidemiology, and End Results (SEER) database. First, bivariate logistic regression analysis was utilized to identify the factors associated with TD and PNI status. Then, patients were divided into four groups, according to TD and PNI status. Propensity score matching (PSM) was performed to balance the baseline covariates. The impact of TD and PNI on survival was assessed by analyzing overall survival (OS) and cancer-specific mortality (CSM) rates. OS was calculated by the Kaplan-Meier method with log-rank analysis. CSM was estimated by competing risk analysis using the Fine and Gray model. RESULTS: A total of 70 689 patients with CRC met the inclusion and exclusion criteria. The positive rates of TD and PNI were 9.37% and 9.91%, respectively. For TD, the most important risk factor was N stage. With respect to PNI, the most significant factor was T stage. Tumor location, tumor size, differentiation grade, and serum CEA level were also correlated with TD and PNI status. After PSM, 1849 pairs were selected. Patients with TD+PNI+ status had the worst 5 year CSM and 5 year OS. In addition, the long-term survival outcomes of patients with TD+PNI- and TD-PNI+ status were comparable. CONCLUSION: The adverse impacts of TD and PNI on the survival of patients with non-metastatic CRC were comparable. CRC patients with both TD and PNI positive had the worst survival outcome.

Long-term oncological outcomes of low anterior resection for rectal cancer with and without preservation of the left colic artery: a retrospective cohort study.

BACKGROUND: There is uncertainty in the literature about preserving the left colic artery (LCA) during low anterior resection for rectal cancer. We analyzed the effect of preserving the LCA on long-term oncological outcomes. METHODS: We retrospectively collected clinicopathological and follow-up details of patients who underwent low anterior resection for rectal cancer in the General Surgery Department of Guangdong Provincial People's Hospital, from January 2014 to December 2015. Cases were divided into low ligation (LL), LCA preserved, or high ligation (HL), LCA not preserved, of the inferior mesenteric artery. The 5-year overall survival (OS) and disease-free survival (DFS) rates were compared between the two groups. RESULTS: Altogether, there were 221 and 295 cases in the LL group and HL groups, respectively. Operating time in the LL group was significantly longer than in the HL group (224.7 vs. 211.7 min, p = 0.039). Postoperative 30-day mortality, early complications including anastomotic leakage showed no significant differences between the LL and HL groups (postoperative 30-day mortality, 0.9% LL, 1.4% HL, p = 0.884; early complications, 41.2% LL, 38.3% HL, p = 0.509; anastomotic leakage 8.6% LL, 13.2% HL, p = 0.100). The median follow-up periods were 51.4 (7-61) months in the LL group and 51.2 (8-61) months in the HL group. During follow-up, the percentages of patients who died, had local recurrence, or had metastases were 39.8, 7.7, and 38.5%, respectively, in the LL group and 39, 8.5, and 40%, respectively, in the HL group; these differences were not significant (all p > 0.05). The 5-year OS and DFS were 69.6 and 59.6% in the LL group, respectively, and 69.1 and 56.2% in the HL group, respectively; these differences were not significant (all p > 0.05). After stratification by tumor-node-metastasis stage, the difference between the 5-year OS and DFS for stages I, II, and III cancer were not significant (all p > 0.05). CONCLUSIONS: The long-term oncological outcomes of LL group are comparable with HL group. LL cannot be supported due to the absence of lower complication rates and the longer operating times.

Realization of Isolated and High-Density Skyrmions at Room Temperature in Uncompensated Synthetic Antiferromagnets.

Magnetic skyrmions are vortex-like spin textures with nontrivial spin topology and novel physical properties that show promise as an essential building block for novel spintronic applications. Skyrmions in synthetic antiferromagnets (SAF) have been proposed long-term to have many advantages than those in ferromagnetic materials, which suffer from fundamental limits for size and efficient manipulation. Thus, experimental realization of skyrmions in SAF is intensely pursued. Here we show the observation of zero-field stable magnetic skyrmions at room temperature in SAF [Co/Pd]/Ru/[Co/Pd] multilayers with Lorentz transmission electron microscope, where uncompensated moments of the SAF provide a medium for the skyrmion characterization. Isolated skyrmions and high-density skyrmions via magnetic field and electromagnetic coordinated methods have been observed, respectively. These created high-density skyrmions maintain at zero-field even when both the current and magnetic field are removed. The use of skyrmions in SAF would advance the process toward practical nonvolatile memories based on spin topology.

Electric field control of Néel spin-orbit torque in an antiferromagnet.

Electric field control of spin-orbit torque in ferromagnets1 has been intensively pursued in spintronics to achieve efficient memory and computing devices with ultralow energy consumption. Compared with ferromagnets, antiferromagnets2,3 have huge potential in high-density information storage because of their ultrafast spin dynamics and vanishingly small stray field4-7. However, the manipulation of spin-orbit torque in antiferromagnets using electric fields remains elusive. Here we use ferroelastic strain from piezoelectric materials to switch the uniaxial magnetic anisotropy in antiferromagnetic Mn2Au films with an electric field of only a few kilovolts per centimetre at room temperature. Owing to the uniaxial magnetic anisotropy, we observe an asymmetric Néel spin-orbit torque8,9 in the Mn2Au, which is used to demonstrate an antiferromagnetic ratchet. The asymmetry of the Néel spin-orbit torque and the corresponding antiferromagnetic ratchet can be reversed by the electric field. Our finding sheds light on antiferromagnet-based memories with ultrahigh density and high energy efficiency.

How to manipulate magnetic states of antiferromagnets.

Antiferromagnetic materials, which have drawn considerable attention recently, have fascinating features: they are robust against perturbation, produce no stray fields, and exhibit ultrafast dynamics. Discerning how to efficiently manipulate the magnetic state of an antiferromagnet is key to the development of antiferromagnetic spintronics. In this review, we introduce four main methods (magnetic, strain, electrical, and optical) to mediate the magnetic states and elaborate on intrinsic origins of different antiferromagnetic materials. Magnetic control includes a strong magnetic field, exchange bias, and field cooling, which are traditional and basic. Strain control involves the magnetic anisotropy effect or metamagnetic transition. Electrical control can be divided into two parts, electric field and electric current, both of which are convenient for practical applications. Optical control includes thermal and electronic excitation, an inertia-driven mechanism, and terahertz laser control, with the potential for ultrafast antiferromagnetic manipulation. This review sheds light on effective usage of antiferromagnets and provides a new perspective on antiferromagnetic spintronics.

Construction of a Biosensor Based on a Combination of Cytochrome c, Graphene, and Gold Nanoparticles.

A biosensor based on a combination of cytochrome c (Cyt c), electrochemical reduced graphene oxides (ERGO), and gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) was fabricated. The proposed biosensor electrode was denoted as GCE/ERGO-Nafion/AuNPs/Cyt c/Nafion, where ERGO-Nafion was deposited by dropping graphene oxides-Nafion mixed droplet first and following electrochemical reduction, AuNPs were directly deposited on the surface of the ERGO-Nafion modified electrode by electrochemical reduction, and other components were deposited by the dropping-dry method. The effect of the deposition amount of AuNPs on direct electrochemistry of Cyt c in the proposed electrode was investigated. The hydrogen peroxide was taken to evaluate the performance of the proposed biosensor. The results showed that the biosensor has great analytical performance, including a high sensitivity, a wide linear range, a low detection limit, and good stability, reproducibility, and reliability.

Activation of semantic information at the sublexical level during handwriting production: Evidence from inhibition effects of Chinese semantic radicals in the picture-word interference paradigm.

Using a non-alphabetic language (e.g., Chinese), the present study tested a novel view that semantic information at the sublexical level should be activated during handwriting production. Over 80% of Chinese characters are phonograms, in which semantic radicals represent category information (e.g., 'chair,' 'peach,' 'orange' are related to plants) while phonetic radicals represent phonetic information (e.g., 'wolf,' 'brightness,' 'male,' are all pronounced /lang/). Under different semantic category conditions at the lexical level (semantically related in Experiment 1; semantically unrelated in Experiment 2), the orthographic relatedness and semantic relatedness of semantic radicals in the picture name and its distractor were manipulated under different SOAs (i.e., stimulus onset asynchrony, the interval between the onset of the picture and the onset of the interference word). Two questions were addressed: (1) Is it possible that semantic information could be activated in the sublexical level conditions? (2) How are semantic and orthographic information dynamically accessed in word production? Results showed that both orthographic and semantic information were activated under the present picture-word interference paradigm, dynamically under different SOAs, which supported our view that discussions on semantic processes in the writing modality should be extended to the sublexical level. The current findings provide possibility for building new orthography-phonology-semantics models in writing.

Antiferromagnetic magnonic charge current generation via ultrafast optical excitation.

Néel spin-orbit torque allows a charge current pulse to efficiently manipulate the Néel vector in antiferromagnets, which offers a unique opportunity for ultrahigh density information storage with high speed. However, the reciprocal process of Néel spin-orbit torque, the generation of ultrafast charge current in antiferromagnets has not been demonstrated. Here, we show the experimental observation of charge current generation in antiferromagnetic metallic Mn2Au thin films using ultrafast optical excitation. The ultrafast laser pulse excites antiferromagnetic magnons, resulting in instantaneous non-equilibrium spin polarization at the antiferromagnetic spin sublattices with broken spatial symmetry. Then the charge current is generated directly via spin-orbit fields at the two sublattices, which is termed as the reciprocal phenomenon of Néel spin-orbit torque, and the associated THz emission can be detected at room temperature. Besides the fundamental significance on the Onsager reciprocity, the observed magnonic charge current generation in antiferromagnet would advance the development of antiferromagnetic THz emitter.

Switching the spin cycloid in BiFeO3 with an electric field.

Bismuth ferrite (BiFeO3) is a multiferroic material that exhibits both ferroelectricity and canted antiferromagnetism at room temperature, making it a unique candidate in the development of electric-field controllable magnetic devices. The magnetic moments in BiFeO3 are arranged into a spin cycloid, resulting in unique magnetic properties which are tied to the ferroelectric order. Previous understanding of this coupling has relied on average, mesoscale measurements. Using nitrogen vacancy-based diamond magnetometry, we observe the magnetic spin cycloid structure of BiFeO3 in real space. This structure is magnetoelectrically coupled through symmetry to the ferroelectric polarization and this relationship is maintained through electric field switching. Through a combination of in-plane and out-of-plane electrical switching, coupled with ab initio studies, we have discovered that the epitaxy from the substrate imposes a magnetoelastic anisotropy on the spin cycloid, which establishes preferred cycloid propagation directions. The energy landscape of the cycloid is shaped by both the ferroelectric degree of freedom and strain-induced anisotropy, restricting the spin spiral propagation vector to changes to specific switching events.

Room-Temperature, Current-Induced Magnetization Self-Switching in A Van Der Waals Ferromagnet.

2D layered materials with broken inversion symmetry are being extensively pursued as  spin source layers to realize high-efficiency magnetic switching. Such low-symmetry layered systems are, however, scarce. In addition, most layered magnets with perpendicular magnetic anisotropy show a low Curie temperature. Here, the experimental observation of spin-orbit torque magnetization self-switching at room temperature in a layered polar ferromagnetic metal, Fe2.5 Co2.5 GeTe2 is reported. The spin-orbit torque is generated from the broken inversion symmetry along the c-axis of the crystal. These results provide a direct pathway toward applicable 2D spintronic devices.

Electrical 180° switching of Néel vector in spin-splitting antiferromagnet.

Antiferromagnetic spintronics have attracted wide attention due to its great potential in constructing ultradense and ultrafast antiferromagnetic memory that suits modern high-performance information technology. The electrical 180° switching of Néel vector is a long-term goal for developing electrical-controllable antiferromagnetic memory with opposite Néel vectors as binary "0" and "1." However, the state-of-art antiferromagnetic switching mechanisms have long been limited for 90° or 120° switching of Néel vector, which unavoidably require multiple writing channels that contradict ultradense integration. Here, we propose a deterministic switching mechanism based on spin-orbit torque with asymmetric energy barrier and experimentally achieve electrical 180° switching of spin-splitting antiferromagnet Mn5Si3. Such a 180° switching is read out by the Néel vector-induced anomalous Hall effect. On the basis of our writing and readout methods, we fabricate an antiferromagnet device with electrical-controllable high- and low-resistance states that accomplishes robust write and read cycles. Besides fundamental advance, our work promotes practical spin-splitting antiferromagnetic devices based on spin-splitting antiferromagnet.

Spin disorder control of topological spin texture.

Stabilization of topological spin textures in layered magnets has the potential to drive the development of advanced low-dimensional spintronics devices. However, achieving reliable and flexible manipulation of the topological spin textures beyond skyrmion in a two-dimensional magnet system remains challenging. Here, we demonstrate the introduction of magnetic iron atoms between the van der Waals gap of a layered magnet, Fe3GaTe2, to modify local anisotropic magnetic interactions. Consequently, we present direct observations of the order-disorder skyrmion lattices transition. In addition, non-trivial topological solitons, such as skyrmioniums and skyrmion bags, are realized at room temperature. Our work highlights the influence of random spin control of non-trivial topological spin textures.

Spin homojunction with high interfacial transparency for efficient spin-charge conversion.

High interfacial transparency is vital to achieve efficient spin-charge conversion for ideal spintronic devices with low energy consumption. However, in traditional ferromagnetic/nonmagnetic heterojunctions, the interfacial Rashba spin-orbit coupling brings about spin memory loss (SML) and two-magnon scattering (TMS), quenching spin current crossing the heterointerfaces. To address the intrinsic deficiency of heterointerface, we design a ferromagnetic FeRh/antiferromagnetic FeRh spin homojunction for efficient spin-charge conversion, verified by a high interfacial transparency of 0.75 and a high spin torque efficiency of 0.34 from spin pumping measurements. First-principles calculations demonstrate that the interfacial electric field of homojunction is two orders of magnitude smaller than that of traditional heterojunction, producing negligible interfacial spin-orbit coupling to drastically reduce SML and TMS. Our spin homojunction exhibits potential and enlightenment for future energy-efficient spintronic devices.

Fabrication of pH-sensitive graphene oxide-Benazepril carrier as biosafety controlled release systems.

A novel graphene oxide (GO)-based carrier was fabricated for the controlled release of Benazepril (BENA). Freeze dried samples of GO-BENA carrier were prepared for controlled drug release at different pHs (pH = 2, 7, and 10) and release kinetics indicate BENA desorption from GO is by Fickian diffusion. The BENA yield from the carrier amounted to ~55% of the adsorbed material in a strongly acidic medium after 50 h. Binding fractions of BENA to 10 mg/L GO was determined for different solution concentrations of the drug. In vitro assays of cell proliferation (WST-1 kit), cell structural integrity (LDH kit) and flow cytometric indicators of necrosis in three different cell lines (CACO-2, SGC-7901, and primary mouse hepatic fibroblast) all demonstrated that the GO carrier had a good biocompatibility. The pH-dependent release sensitivity of the GO-based carrier suggests that it is a potential candidate for use in the controlled release of drugs in the acidic environment of the stomach.

Amplified Analysis of DNA or Proteins by TdT-generated DNAzyme.

Sensitive and specific detection of nucleic acids or proteins, which act as biomarkers, is of great importance in disease diagnosis. By combing the concept and operation of an endonuclease-assisted target-responsive amplification method and peroxidase-mimic DNAzyme generated by terminal deoxynucleotidyl transferase (TdT), a novel and facile colorimetric biosensor was developed for DNA and protein. Target DNA and thrombin were chosen as representative biomolecules. The production of cleavage fragments can only be triggered by specific target binding and the following nicking process, which do not occur spontaneously. In the signal collection part, numerous guanine-rich DNA were produced through the prolongation of cleavage fragments by TdT and formed highly effective DNAzyme with hemin. In this novel amplification method, we succeeded in realizing sensitive and specific detection of target DNA and thrombin. Under optimal conditions, target DNA can be detected as low as 1 pM, and thrombin with a detection limit of 100 pM. The method also proves the potential versatility and feasibility of TdT-generated DNAzyme in various bio-analyses.