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Giant and tunneling magnetoresistance are physical phenomena used for reading information in commercial spintronic devices. The effects rely on a conserved spin current passing between a reference and a sensing ferromagnetic electrode in a multilayer structure. Recently, we have proposed that these fundamental spintronic effects can be realized in unconventional collinear antiferromagnets with nonrelativistic alternating spin-momentum coupling. Here, we elaborate on the proposal by presenting archetype model mechanisms for the giant and tunneling magnetoresistance effects in multilayers composed of these unconventional collinear antiferromagnets. The models are based, respectively, on anisotropic and valley-dependent forms of the alternating spin-momentum coupling. Using first-principles calculations, we link these model mechanisms to real materials and predict an approximately 100% scale for the effects. We point out that, besides the giant or tunneling magnetoresistance detection, the alternating spin-momentum coupling can allow for magnetic excitation by the spin-transfer torque.

In a Dirac semimetal, each Dirac node is resolved into two Weyl nodes with opposite \"handedness\" or chirality. The two chiral populations do not mix. However, in parallel electric and magnetic fields (EǀǀB), charge is predicted to flow between the Weyl nodes, leading to negative magnetoresistance. This \"axial\" current is the chiral (Adler-Bell-Jackiw) anomaly investigated in quantum field theory. We report the observation of a large, negative longitudinal magnetoresistance in the Dirac semimetal Na3Bi. The negative magnetoresistance is acutely sensitive to deviations of the direction of B from E and is incompatible with conventional transport. By rotating E (as well as B), we show that it is consistent with the prediction of the chiral anomaly.

In this paper, a practical model structure capable of being a non-contact system is derived and investigated. A magnetoresistance model is established. By analysing several influencing factors affecting the transformer core, and on the basis of the traditional transformer according to the design formula of the transformer, according to the electromagnetic geometric relationship and the multi-objective optimization algorithm, the design process of the ipt system is improved by using electromagnetic simulation analysis.

An electrical current running through two stacked magnetic layers is larger if their magnetizations point in the same direction than if they point in opposite directions. These so-called magnetic tunnel junctions, used in electronics, must be carefully engineered. Two groups now show that high magnetoresistance intrinsically occurs in samples of the layered material CrI 3 sandwiched between graphite contacts. By varying the number of layers in the samples, Klein et al. and Song et al. found that the electrical current running perpendicular to the layers was largest in high magnetic fields and smallest near zero field. This observation is consistent with adjacent layers naturally having opposite magnetizations, which align parallel to each other in high magnetic fields. Science , this issue p. 1218 , p. 1214 The atomic layers of the material CrI 3 act as spin filters in graphite/CrI 3 /graphite junctions. Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI 3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and interlayer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI 3 barriers, respectively. We further measure inelastic tunneling spectra for our junctions, unveiling a rich spectrum consistent with collective magnetic excitations (magnons) in CrI 3 .

Implementations of artificial neural networks that borrow analogue techniques could potentially offer low-power alternatives to fully digital approaches 1 – 3 . One notable example is in-memory computing based on crossbar arrays of non-volatile memories 4 – 7 that execute, in an analogue manner, multiply–accumulate operations prevalent in artificial neural networks. Various non-volatile memories—including resistive memory 8 – 13 , phase-change memory 14 , 15 and flash memory 16 – 19 —have been used for such approaches. However, it remains challenging to develop a crossbar array of spin-transfer-torque magnetoresistive random-access memory (MRAM) 20 – 22 ,  despite the technology’s practical advantages such as endurance and large-scale commercialization 5 . The difficulty stems from the low resistance of MRAM, which would result in large power consumption in a conventional crossbar array that uses current summation for analogue multiply–accumulate operations. Here we report a 64 × 64 crossbar array based on MRAM cells that overcomes the low-resistance issue with an architecture that uses resistance summation for analogue multiply–accumulate operations. The array is integrated with readout electronics in 28-nanometre complementary metal–oxide–semiconductor technology. Using this array, a two-layer perceptron is implemented to classify 10,000 Modified National Institute of Standards and Technology digits with an accuracy of 93.23 per cent (software baseline: 95.24 per cent). In an emulation of a deeper, eight-layer Visual Geometry Group-8 neural network with measured errors, the classification accuracy improves to 98.86 per cent (software baseline: 99.28 per cent). We also use the array to implement a single layer in a ten-layer neural network to realize face detection with an accuracy of 93.4 per cent. A crossbar array of magnetic memory to execute analogue in-memory computing has been developed, and performs image classification and facial detection at low power.

Understanding the competition between superconductivity and other ordered states (such as antiferromagnetic or charge-density-wave (CDW) state) is a central issue in condensed matter physics. The recently discovered layered kagome metal A V 3 Sb 5 ( A  = K, Rb, and Cs) provides us a new playground to study the interplay of superconductivity and CDW state by involving nontrivial topology of band structures. Here, we conduct high-pressure electrical transport and magnetic susceptibility measurements to study CsV 3 Sb 5 with the highest T c of 2.7 K in A V 3 Sb 5 family. While the CDW transition is monotonically suppressed by pressure, superconductivity is enhanced with increasing pressure up to P1 ≈ 0.7 GPa, then an unexpected suppression on superconductivity happens until pressure around 1.1 GPa, after that, T c is enhanced with increasing pressure again. The CDW is completely suppressed at a critical pressure P2 ≈ 2 GPa together with a maximum T c of about 8 K. In contrast to a common dome-like behavior, the pressure-dependent T c shows an unexpected double-peak behavior. The unusual suppression of T c at P1 is concomitant with the rapidly damping of quantum oscillations, sudden enhancement of the residual resistivity and rapid decrease of magnetoresistance. Our discoveries indicate an unusual competition between superconductivity and CDW state in pressurized kagome lattice. The recently discovered kagome metal A V 3 Sb 5 is a new playground to study the interplay between superconductivity and charge-density-wave (CDW) state. Here, the authors report pressure-dependent evolution of CDW and superconductivity in CsV 3 Sb 5 , suggesting an unusual competition between the two phases.

This article summarizes the commonly used in magnetic sensors Hall sensors, Anisotropic magnetoresistive sensor (AMR), Giant magnetoresistance effect sensor (GMR) and Tunneling magnetoresistance sensor (TMR). The structure and working principle of each sensor are introduced. In addition, some error sources of magnetic sensors and the calibration techniques used are introduced, and some typical application examples of each sensor are introduced.

An electrical current running through two stacked magnetic layers is larger if their magnetizations point in the same direction than if they point in opposite directions. These so-called magnetic tunnel junctions, used in electronics, must be carefully engineered. Two groups now show that high magnetoresistance intrinsically occurs in samples of the layered material CrI 3 sandwiched between graphite contacts. By varying the number of layers in the samples, Klein et al. and Song et al. found that the electrical current running perpendicular to the layers was largest in high magnetic fields and smallest near zero field. This observation is consistent with adjacent layers naturally having opposite magnetizations, which align parallel to each other in high magnetic fields. Science , this issue p. 1218 , p. 1214 The atomic layers of the material CrI 3 act as spin filters in graphite/CrI 3 /graphite junctions. Magnetic multilayer devices that exploit magnetoresistance are the backbone of magnetic sensing and data storage technologies. Here, we report multiple-spin-filter magnetic tunnel junctions (sf-MTJs) based on van der Waals (vdW) heterostructures in which atomically thin chromium triiodide (CrI 3 ) acts as a spin-filter tunnel barrier sandwiched between graphene contacts. We demonstrate tunneling magnetoresistance that is drastically enhanced with increasing CrI 3 layer thickness, reaching a record 19,000% for magnetic multilayer structures using four-layer sf-MTJs at low temperatures. Using magnetic circular dichroism measurements, we attribute these effects to the intrinsic layer-by-layer antiferromagnetic ordering of the atomically thin CrI 3 . Our work reveals the possibility to push magnetic information storage to the atomically thin limit and highlights CrI 3 as a superlative magnetic tunnel barrier for vdW heterostructure spintronic devices.

Electric currents carrying a net spin polarization are widely used in spintronics, whereas globally spin-neutral currents are expected to play no role in spin-dependent phenomena. Here we show that, in contrast to this common expectation, spin-independent conductance in compensated antiferromagnets and normal metals can be efficiently exploited in spintronics, provided their magnetic space group symmetry supports a non-spin-degenerate Fermi surface. Due to their momentum-dependent spin polarization, such antiferromagnets can be used as active elements in antiferromagnetic tunnel junctions (AFMTJs) and produce a giant tunneling magnetoresistance (TMR) effect. Using RuO 2 as a representative compensated antiferromagnet exhibiting spin-independent conductance along the [001] direction but a non-spin-degenerate Fermi surface, we design a RuO 2 /TiO 2 /RuO 2 (001) AFMTJ, where a globally spin-neutral charge current is controlled by the relative orientation of the Néel vectors of the two RuO 2 electrodes, resulting in the TMR effect as large as ~500%. These results are expanded to normal metals which can be used as a counter electrode in AFMTJs with a single antiferromagnetic layer or other elements in spintronic devices. Our work uncovers an unexplored potential of the materials with no global spin polarization for utilizing them in spintronics. Spin-polarised electric currents have been studied extensively for use in spintronics, while their spin-neutral counterparts have been largely ignored. Here Shao et al show that such spin-neutral currents can be controlled by the Neel vector orientation of an antiferromagnet and detected using an antiferromagnetic tunnel junction.

The results of measurements of electrical resistivity without a field and in magnetic field of 0.8 T in the temperature range 100 K < T < 450 K for compositionYbxMn1-xS with x = 0.05, 0.1 are presented. For the x = 0.05 the gigantic magnetoresistive effect at room temperature is found.