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Out-of-plane spin polarization σ z has attracted increasing interests of researchers recently, due to its potential in high-density and low-power spintronic devices. Noncollinear antiferromagnet (AFM), which has unique 120° triangular spin configuration, has been discovered to possess σ z . However, the physical origin of σ z in noncollinear AFM is still not clear, and the external magnetic field-free switching of perpendicular magnetic layer using the corresponding σ z has not been reported yet. Here, we use the cluster magnetic octupole in antiperovskite AFM Mn 3 SnN to demonstrate the generation of σ z . σ z is induced by the precession of carrier spins when currents flow through the cluster magnetic octupole, which also relies on the direction of the cluster magnetic octupole in conjunction with the applied current. With the aid of σ z , current induced spin-orbit torque (SOT) switching of adjacent perpendicular ferromagnet is realized without external magnetic field. Our findings present a new perspective to the generation of out-of-plane spin polarizations via noncollinear AFM spin structure, and provide a potential path to realize ultrafast high-density applications. One consistent challenge in spintronics is electrical control of the magnetisation. Here, You et al demonstrate switching of magnetisation in a heterostucture composed of Mn3SnN and Permalloy, making use of the out-of-plane spin polarization induced by currents in the antiferromagnetic Mn3SnN.

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.

In conventional ferromagnet/spacer/ferromagnet sandwiches, noncollinear couplings are commonly absent because of the low coupling energy and strong magnetization. For antiferromagnets (AFM), the small net moment can embody a low coupling energy as a sizable coupling field, however, such AFM sandwich structures have been scarcely explored. Here we demonstrate orthogonal interlayer coupling at room temperature in an all-antiferromagnetic junction Fe 2 O 3 /Cr 2 O 3 /Fe 2 O 3 , where the Néel vectors in the top and bottom Fe 2 O 3 layers are strongly orthogonally coupled and the coupling strength is significantly affected by the thickness of the antiferromagnetic Cr 2 O 3 spacer. From the energy and symmetry analysis, the direct coupling via uniform magnetic ordering in Cr 2 O 3 spacer in our junction is excluded. The coupling is proposed to be mediated by the non-uniform domain wall state in the spacer. The strong long-range coupling in an antiferromagnetic junction provides an unexplored approach for designing antiferromagnetic structures and makes it a promising building block for antiferromagnetic devices. Ferromagnet/spacer/ferromagnet sandwiches have been studied extensively, and used in a variety of spintronic devices. Here, Zhou et al. create an all anti-ferromagnetic sandwich of Fe 2 O 3 /Cr 2 O 3 /Fe 2 O 3 , and demonstrate strong orthogonal coupling between the top and bottom Fe 2 O 3 layers.

Antiferromagnetic materials, which have ordered but alternating magnetic moments, exhibit fast spin dynamics and produce negligible stray fields, and could be used to build high-density, high-speed memory devices with low power consumption. However, the efficient electrical detection and manipulation of antiferromagnetic moments is challenging. Here we show that the spin current and antiferromagnetic moments in the topological insulator/antiferromagnetic insulator bilayer (Bi,Sb) 2 Te 3 /α-Fe 2 O 3 can be controlled via topological surface states. In particular, the orientation of the antiferromagnetic moments in α-Fe 2 O 3 can modulate the spin current reflection at the bilayer interface. In turn, the spin current can control the moment rotation in the antiferromagnetic insulator by means of a giant spin–orbit torque generated by the topological surface state. The required threshold switching current density is 3.5 × 10 6  A cm −2 at room temperature, which is one order of magnitude smaller than that required in heavy-metal/antiferromagnetic insulator systems. The antiferromagnetic moments in the topological insulator/antiferromagnetic insulator bilayer (Bi,Sb) 2 Te 3 /α-Fe 2 O 3 can be reversibly switched using electrical currents at room temperature, and with a critical current density that is one order of magnitude smaller than that required in heavy-metal/magnetic insulator systems.

Purpose The purpose of this study was to determine the reliability of applying conventional anatomical landmarks to locate venous sinus in posterior fossa using subtraction computed tomography angiography (CTA) technique. Methods We retrospectively reconstructed transverse sinus (TS), sigmoid sinus (SS), and cranial imaging from 100 patients undergoing head CTA examination. Subtraction CTA data was merged with nonenhanced data and then cranium transparency was adjusted to 50% on three-dimensional volume rendering, indicating the anatomical relationship between surface landmarks of cranium and confluens sinuum, TS, and SS. Results CTA technique precisely displayed the anatomical relations between venous sinus in posterior fossa and cranial surface landmarks. The asterion was located directly over the transverse–sigmoid sinus junction (TSST) in 81% cases, inferior to TSST in 15%, and superior to TSST in 4%, mainly distributing on the TS side of TSST, namely the distal-end of TS. Superior nuchal line had complex relation with TS and the line drawn from the zygoma root to the inion (LZI), but failed to represent the location of TS and the trend of LZI. In proximal-end of TS, majority of LZI overlapped with TS line. However, most LZI was gradually positioned below TS line as TS moved outwards. Almost half of line drawn from the squamosal–parietomastoid suture junction to the inion and line drawn from the asterion to the inion shared the same trend with TS. Conclusion Subtraction CTA merged into nonenhanced cranial bone with 50% skull transparency provides a feasible method to identify the anatomical relation between venous sinus and surface landmarks of cranium, which is significantly varied among individuals, so it is not accurate to determine venous sinus in posterior fossa merely using surface landmarks.

Out-of-plane spin polarization {\\sigma}_z has attracted increasing interests of researchers recently, due to its potential in high-density and low-power spintronic devices. Noncollinear antiferromagnet (AFM), which has unique 120{\\deg} triangular spin configuration, has been discovered to possess {\\sigma}_z. However, the physical origin of {\\sigma}_z in noncollinear AFM is still not clear, and the external magnetic field-free switching of perpendicular magnetic layer using the corresponding {\\sigma}_z has not been reported yet. Here, we use the cluster magnetic octupole in antiperovskite AFM Mn3SnN to demonstrate the generation of {\\sigma}_z. {\\sigma}_z is induced by the precession of carrier spins when currents flow through the cluster magnetic octupole, which also relies on the direction of the cluster magnetic octupole in conjunction with the applied current. With the aid of {\\sigma}_z, current induced spin-orbit torque (SOT) switching of adjacent perpendicular ferromagnet is realized without external magnetic field. Our findings present a new perspective to the generation of out-of-plane spin polarizations via noncollinear AFM spin structure, and provide a potential path to realize ultrafast high-density applications.

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.

Anomalous Nernst effect (ANE), the generation of a transverse electric voltage by a longitudinal temperature gradient, has attracted increasing interests of researchers recently, due to its potential in the thermoelectric power conversion and close relevance to the Berry curvature of the band structure. Avoiding the stray field of ferromagnets, ANE in antiferromagnets (AFM) has the advantage of realizing highly efficient and densely integrated thermopiles. Here, we report the observation of ANE in an antiperovskite noncollinear AFM Mn3SnN experimentally, which is triggered by the enhanced Berry curvature from Weyl points located close to the Fermi level. Considering that antiperovskite Mn3SnN has rich magnetic phase transition, we modulate the noncollinear AFM configurations by the biaxial strain, which enables us to control its ANE. Our findings provide a potential class of materials to explore the Weyl physics of noncollinear AFM as well as realizing antiferromagnetic spin caloritronics that exhibits promising prospects for energy conversion and information processing.

Magnetotransport is at the center of the spintronics. Mn3Sn, an antiferromagnet that has a noncollinear 120{\\deg} spin order, exhibits large anomalous Hall effect (AHE) at room temperature. But such a behavior has been remained elusive in Mn3Sn films. Here we report the observation of robust AHE up to room temperature in quasi-epitaxial Mn3Sn thin films, prepared by magnetron sputtering. The growth of both (11-20)- and (0001)-oriented Mn3Sn films provides a unique opportunity for comparing AHE in three different measurement configurations. When the magnetic field is swept along (0001) plane, such as the direction of [01-10] and [2-1-10] the films show comparatively higher anomalous Hall conductivity than its perpendicular counterpart ([0001]), irrespective of their respectively orthogonal current along [0001] or [01-10]. A quite weak ferromagnetic moment of 3 emu/cm^3 is obtained in (11-20)-oriented Mn3Sn films, guaranteeing the switching of the Hall signals with magnetization reversal. Our finding would advance the integration of Mn3Sn in antiferromagnetic spintronics.