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Manipulation of the magnetization by spin‐orbit torque (SOT) stands as a crucial advancement in spintronics due to its merits in energy‐efficient and high‐speed operation. However, the conventional SOT devices involving a heavy metal/ferromagnet cannot deterministically switch the perpendicularly magnetized ferromagnet without an external magnetic field, which hinders its practical implementation. Here, room temperature field‐free switching for perpendicularly magnetized ferromagnets is demonstrated using spin currents with the out‐of‐plane spin polarization induced by noncollinear antiferromagnets L12‐Mn3Ir. Both in‐plane and out‐of‐plane spin polarizations are observed, and the tilting angle of the spin polarization is estimated to be ≈10°. The spin Hall conductivity of out‐of‐plane spin is 1.43 × 104 ћ/2e·Ω−1m−1, which is the largest among several 2D and antiferromagnetic materials, including WTe2, RuO2, and Mn3GaN. Furthermore, field‐free SOT switching is demonstrated with an ns‐current pulse, and the current density is comparable with the reported values of the field‐assisted pulse switching. This work paves the way for employing noncollinear antiferromagnets for wafer‐scale spintronic device applications. [ABSTRACT FROM AUTHOR]

We have theoretically investigated the Andreev reflection (AR)-induced conductance spectra through antiferromagnet/normal layer/superconductor junctions with hexagonal lattices. When the PT symmetry is broken by the staggered sublattice potential, antiferromagnet may exhibit spin polarization. A gap-edge conductance peak is usually shown, reflecting the characteristic of conventional AR. Equal-spin AR can be generated by the spin-flip scattering caused by Rashba spin–orbit coupling in the normal layer. Surprisingly, when the equal-spin AR process dominates, the conductance peak divides into two peaks near the singlet-gap energy, indicating the existence of spin-triplet pairings in the antiferromagnet. Furthermore, as the amplitudes of the conventional and equal-spin ARs can be modulated by the staggered sublattice potential and electrostatic potential, a conversion from the conductance peak to the conductance peak splitting can be realized, which can help us to distinguish between the spin-singlet and spin-triplet pairings. These findings make the antiferromagnet/superconductor junctions as promising platforms for future superconducting spintronics applications. [ABSTRACT FROM AUTHOR]

We discuss the correspondence between the current-induced spin polarization in non-centrosymmetric magnetic metals and the linear magnetoelectric effect in non-centrosymmetric magnetic insulators using a linear-response theory and the concept of magnetoelectric multipoles. We show that the magnetoelectric toroidal moment is a particularly useful quantity since it determines the ground-state antiferromagnetic domain of a non-centrosymmetric antiferromagnet in the presence of a steady-state electric current. We analyze two prototypical antiferromagnetic spintronic materials— Mn 2 Au and CuMnAs—and show that the experimentally reported domain reorientations are consistent with the alignment of their toroidal moments parallel to the applied electric current. Finally, we determine whether similar behavior should be expected in the prototypical insulating magnetoelectric materials, Cr 2 O 3 and Li M PO 4 , if they could be doped into a semiconducting or metallic regime. [ABSTRACT FROM AUTHOR]

In the current stage, valley-contrasting physics is mainly rooted in nonmagnetic and/or ferromagnetic hexagonal lattices and is rarely used to observe the simultaneous spin and valley polarization in antiferromagnetic materials. In this work, we propose a general scheme that can be achieved easily in experiments to break the P T joint symmetry of antiferromagnetic structures, that is, introducing an out-of-plane potential gradient to realize spin–valley splitting and spontaneous valley polarization. In combination of the model analysis and first-principles calculations, we translate the concept into Mn2P2X3Y3 monolayers and clarify the valley-related physics. It is obvious that our finding significantly extends the scope of valleytronics in both theory and experiments. [ABSTRACT FROM AUTHOR]

Manipulating spin polarization orientation is challenging but crucial for field-free spintronic devices. Although such manipulation has been demonstrated in a limited number of antiferromagnetic metal-based systems, the inevitable shunting effects from the metallic layer can reduce the overall device efficiency. In this study, we propose an antiferromagnetic insulator-based heterostructure NiO/Ta/Pt/Co/Pt for such spin polarization control without any shunting effect in the antiferromagnetic layer. We show that zero-field magnetization switching can be realized and is related to the out-of-plane component of spin polarization modulated by the NiO/Pt interface. The zero-field magnetization switching ratio can be effectively tuned by the substrates, in which the easy axis of NiO can be manipulated by the tensile or compressive strain from the substrates. Our work demonstrates that the insulating antiferromagnet based heterostructure is a promising platform to enhance the spin-orbital torque efficiency and achieve field-free magnetization switching, thus opening an avenue towards energy-efficient spintronic devices. Electrically switching perpendicular magnetized ferromagnets using spin-orbit torques without assisting magnetic fields is a major goal for spintronics. Recently, several works have proposed using out-of-plane spin polarized currents to achieve this, but these rely on antiferromagnetic metals with low Neel temperatures. Here, Wang et al show that such out-of-plane spin polarization driven switching can be achieved using the interface of an antiferromagnetic insulator and a heavy metal. [ABSTRACT FROM AUTHOR]

Non‐covalent hybrid materials based on graphene and A3‐type copper corrole complexes were computationally investigated. The corroles complexes contain strong electron‐withdrawing fluorinated substituents at the meso positions. Our results show that the non‐innocent character of corrole moiety modulates the structural, electronic, and magnetic properties once the hybrid systems are held. The graphene‐corrole hybrids displayed outstanding stability via the interplay of dispersion and electrostatic driving forces, while graphene act as an electron reservoir. The hybrid structures exposed an intriguing magneto‐chemical performance, compared to the isolated counterparts, that evidenced how structural and electronic effects contributed to the magnetic response for both ferromagnetic and antiferromagnetic cases. Directional spin polarization and spin transfer from the corrole to the graphene surface participate in the amplification. Finally, there are relations between the spin transfer, the magnetic response, and the copper distorted ligand field, offering exciting hints about modulating the magnetic response. Therefore, this work shows that copper corroles emerged as versatile building blocks for graphene hybrid materials, especially in applications requiring a magnetic response. [ABSTRACT FROM AUTHOR]

Herein, a comparative computational study inquiring about ground state magnetic properties of a nanometer‐size bowtie graphene quantum dot with an AA‐stacking bilayer trapezoid counterpart based on the single‐orbital Hubbard model and density functional theory (DFT) is presented. The structures have an antiferromagnetic ground state with a 1‐to‐1 correspondence between the local spin polarizations of the two systems. The tight‐binding energy spectra look different. However, a similar fashion in the energy spectra emerges after considering the Hubbard interaction term. A comparison between the spatial distributions of edge states shows that the wave functions in both structures are sublattice polarized by proposing a specific unit cell in the bilayer case. In addition, the on‐site coulombic repulsion consequence on the rising of magnetization and the size of the local magnetic moment has been considered. [ABSTRACT FROM AUTHOR]

Vertical stacks of graphene and ferromagnetic layers are predicted to be efficient spin filters, while the experimentally observed figures of merit systematically remain below the theoretical predictions. According to general consensus, a vaguely defined interface contamination is found responsible for this discrepancy. Here, it is demonstrated how the spin‐polarized electronic structure of single‐layer graphene supported on a ferromagnetic cobalt substrate is affected by the presence of an interfacial carbidic buffer layer, formed by residual carbon present in the Co substrate. It is found that the Co‐C hybridized single‐spin state near the Fermi level disappears upon thermal segregation of bulk carbon at the graphene–Co interface, which determines the electronic decoupling of graphene from the ferromagnetic support and consequently, the suppression of net spin polarization. These observations are shown to be independent of the graphene azimuthal orientation with respect to the high symmetry directions of the substrate. The findings provide clear evidence that the realization of highly polarized spin currents in graphene/ferromagnet heterostacks depends on careful control of the graphene growth process in order to eliminate interfacial carbon. [ABSTRACT FROM AUTHOR]

Antiferromagnetic (AFM) spintronics is an emerging field, with significant advances in particular in the study of the tunable spin generation, transport, manipulation, and detection based on the control and probe of AFM moments. The Néel-vector-dependent spin current generation in AFM materials makes them an efficient and controllable spin source, paving the way for future spintronic devices with ultralow power consumption and high operability. Herein, we aim to provide a comprehensive review of recent progress in charge-spin conversion mediated by AFMs. First, we present a brief summary of several typical characterization techniques of charge-spin conversion. Then, we focus on the recent efforts for improving the charge-spin conversion efficiency and performances of spin torques in the antiferromagnet/ferromagnet bilayer. In the third part, we review the controllable spin current and multidirectional spin polarization generated by AFMs and the resultant field-free magnetization switching. Finally, we discuss the prospects of the AFM spin sources, which will inspire more in-depth studies and advance practical applications. [ABSTRACT FROM AUTHOR]

Based on first-principles band-structure calculations, we predict that FM MnHg2Te3 is a Weyl semimetal candidate. When the direction of spin polarization is toward the c-axis, there are six Weyl points in the whole Brillouin zone. With spin orientation along the a-axis, there exist eight Weyl points. For AFM MnHg2Te3, when the spin direction is along the c-axis, the band structure is fully gapped. The calculation of the Z2 number confirms that AFM-c MnHg2Te3 is a 3D AFM topological insulator. Adjusting the spin direction from the c-axis to the a-axis only changes the bandgap without affecting the topological properties of this system. The gapless surface-state on the (100) surface is also obtained, the results of which correspond with the properties of the AFM topological insulator. [ABSTRACT FROM AUTHOR]

Based on first-principles band-structure calculations, we predict that FM MnHg2Te3 is a Weyl semimetal candidate. When the direction of spin polarization is toward the c-axis, there are six Weyl points in the whole Brillouin zone. With spin orientation along the a-axis, there exist eight Weyl points. For AFM MnHg2Te3, when the spin direction is along the c-axis, the band structure is fully gapped. The calculation of the Z2 number confirms that AFM-c MnHg2Te3 is a 3D AFM topological insulator. Adjusting the spin direction from the c-axis to the a-axis only changes the bandgap without affecting the topological properties of this system. The gapless surface-state on the (100) surface is also obtained, the results of which correspond with the properties of the AFM topological insulator. [ABSTRACT FROM AUTHOR]

The development of two-dimensional (2D) magnetic semiconductors promotes the study of nonvolatile control of magnetoelectric nanodevices. MnBi2Te4 is the first realization of antiferromagnetic topological insulator. In semiconductor circuits, metal-semiconductor contacts are usually essential. In future all-carbon circuits, graphene is a promising material for 2D conductive connections. This work studies electronic transport through graphene-MnBi2Te4-graphene junctions. We find that graphene-MnBi2Te4 interfaces are perfect Ohmic contacts, which benefits the use of MnBi2Te4 in carbon circuits. The currents through MnBi2Te4 junctions possess high spin polarization. Compared with usual van der Waals junctions, lateral graphene-MnBi2Te4-graphene junctions present a lower barrier and much higher conductance to electrons. These findings may provide guidance for further study of 2D spin filtering. [ABSTRACT FROM AUTHOR]

Adjusting the spin polarization of carbon nanotubes is critical for achieving functional applications of spintronic devices such as magnetic switches. Herein, heterojunction carbon nanotubes (HCNTs) are constructed by connecting two different zigzag edges to achieve this goal. First‐principles calculations indicate spin ferromagnetic (FM) or antiferromagnetic (AFM) coupling in the corresponding structure, which can be regulated by the number of carbon atoms at the zigzag edges of the HCNTs. Further calculations related to the charged HCNTs indicate that electronic ground states of the same structure can be transformed from spin AFM to spin FM coupling states. Thus, the behavior of spin polarization for zigzag–zigzag HCNTs can also be regulated by the charge. This finding opens up a new approach for spin adjustment, which can potentially contribute to the design of spintronic devices. [ABSTRACT FROM AUTHOR]

Magnon excitations in antiferromagnetic materials and their physical implications have helped to facilitate the emergence of device concepts not presently available in ferromagnets. A unique characteristic of antiferromagnetic magnons is the coexistence of opposite spin polarization, which mimics the electron spin in a variety of transport phenomena. Among them, the most prominent spin-contrasting phenomenon is the magnon spin Nernst effect (SNE), which refers to the generation of a transverse pure magnon spin current through a longitudinal temperature gradient. We introduce selected recent progress in the study of magnon SNE in collinear antiferromagnets with focus on its underlying physical mechanism entailing profound topological features of magnon band structures. By reviewing how the magnon SNE has inspired and enriched the exploration of topological magnons, we offer our perspective on this emerging frontier that holds potential in future spintronic nano-technology. [ABSTRACT FROM AUTHOR]

Antiferromagnets offer unique advantages in the development of spintronics because of the absence of stray field, insensitivity to external disturbances and the ultrafast terahertz eigenfrequency, advancing the development of devices toward small‐size and high‐speed. However, the ultralow read‐out signals of antiferromagnetic spintronics are notoriously smaller than their ferromagnetic counterpart, seriously hindering the development of antiferromagnets. Thus, experimental realization of large read‐out signals in antiferromagnets, especially in vertical devices, is intensely pursued. Here the antiferromagnetic magnon drag effect and a giant on–off ratio of ≈1000 are realized in a vertical sandwich structure of heavy metal/antiferromagnetic insulator/heavy metal (Pt/α‐Fe2O3/Pt). The read‐out signal can exist up to room temperature, and the detected signal owing to the transmission and blocking of magnon strongly relies on the relative orientation between spin polarization and Néel vector. Benefiting from the nonvolatile characteristic of Fe2O3, zero‐field vertical magnon transport is achieved. The giant on–off signals in vertical devices that can be tightly packed, can greatly promote the practical application of antiferromagnetic magnon devices toward smaller, faster, and lower energy consumption. [ABSTRACT FROM AUTHOR]

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 RuO2 as a representative compensated antiferromagnet exhibiting spin-independent conductance along the [001] direction but a non-spin-degenerate Fermi surface, we design a RuO2/TiO2/RuO2 (001) AFMTJ, where a globally spin-neutral charge current is controlled by the relative orientation of the Néel vectors of the two RuO2 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. [ABSTRACT FROM AUTHOR]

The formation of a magnetic order in a three-dimensional topological insulator is manifested in the behavior of electronic states at its boundaries. The modification of the surface electronic structure under the effect of a noncollinear domain-wall magnetization texture appearing in an intrinsic antiferromagnetic topological insulator is theoretically studied in this work. It is shown that a bound one-dimensional state induced by a domain wall appears in addition to the modulation of the surface exchange gap and the shift of the two-dimensional Dirac cone in the momentum space. The main characteristics of the bound state such as the energy spectrum, spin polarization, spatial localization, and their dependence on the mutual orientation of magnetizations in domains are described. Methods of the experimental detection of a one-dimensional state associated with a domain wall, as well as a possible contribution of this state to new quantum effects, on the surface of the antiferromagnetic topological insulator such as MnBi2Te4 are discussed. [ABSTRACT FROM AUTHOR]

Out-of-plane spin polarization σz 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 σz. However, the physical origin of σz in noncollinear AFM is still not clear, and the external magnetic field-free switching of perpendicular magnetic layer using the corresponding σz has not been reported yet. Here, we use the cluster magnetic octupole in antiperovskite AFM Mn3SnN to demonstrate the generation of σz. σz 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 σz, 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. [ABSTRACT FROM AUTHOR]

Antiferromagnets are promising materials for memory devices owing to their ultrafast spin dynamics. For efficient control of antiferromagnets, a direct interaction between the spin current and local magnetization of the sublattice is required. In this study, we demonstrated that a short-pulsed spin current can induce fast dynamics of metallic antiferromagnets of PtMn and IrMn via spin-transfer torque on the magnetization of sublattices. We employed two methods to generate a short-pulsed spin current, namely ultrafast demagnetization of a ferromagnet and optical spin polarization of a heavy metal. The magnetization dynamics were measured using the time-resolved magneto-optical Kerr effect and were analyzed using the Landau–Lifshitz–Gilbert equation. Our results provide important evidence of the direct interaction between the magnetization of antiferromagnets and spin current. [ABSTRACT FROM AUTHOR]

Antiferromagnetic materials are expected to trigger the revolution of spintronic applications because they are robust against the perturbation of magnetic fields, produce no stray fields, and display ultrafast dynamics. To design antiferromagnetic devices, the generation and manipulation of spin-polarized current in antiferromagnetic materials are vital. Unfortunately, it has long been believed that spin-polarized current could not be achieved in collinear antiferromagnetic materials because of the symmetry of spin sublattices. Inspired by the possibility of breaking the symmetry using a bias voltage, a special Au/NiO/Au junction is proposed and constructed along the [111] direction of NiO using the collinear NiO antiferromagnetic insulator as a prototype. It was found that the symmetry of spin sublattices was broken by an external bias, which induces a nonequivalent transport for spin-up and spin-down currents, that is, the appearance of spin-polarized current. Unexpectedly, this study found that the magnitude and sign of spin polarization could be adjusted by varying the bias. A positive spin polarization up to 80% was obtained at ∼ 0.9 V, and the spin polarization turned negative when the bias voltage was beyond 1.6 V. The related physical mechanisms were explored and clarified by analyzing spin-resolved transmission, kǁ-resolved density of states, and layer-resolved local density of states of Au/NiO/Au, etc. The effects of NiO layer thicknesses, different electrodes, and interfacial disorders on the spin polarization were also analyzed and found to offer promising applications. This study provides new physical insight into spin-polarized current transport in collinear antiferromagnetic materials and greatly contributes to the development of novel antiferromagnetic spintronic devices. [ABSTRACT FROM AUTHOR]

Mn2PtSn tetragonal is promising for spintronic devices, especially for spin-transfer-torque based devices. We apply the density functional theory formalism to make a detailed study of the structural, magnetic, and electronic properties for Mn2PtSn crystals. The dependence of the elastic constants Cij for cubic and tetragonal structure, the aggregate elastic moduli B, G, and the anisotropy A, along with the related mechanical properties are investigated. The Curie temperatures and the magnetic moments in both the cubic as well as tetragonal phases have been calculated. Mn2PtSn can be studied in inverse tetragonal crystal structure with antiferromagnetic spin order. Because of the high magnetic anisotropy, low magnetization, and high spin polarization at the Fermi level, this material is expected to be promising for spin-transfer-torque applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Spin-polarized field emitter using antiferromagnetic Cr thin film on W(0 0 1) facet. • The maximum spin polarization of 50% at room temperature. • The stable value and direction of spin polarization over 3 h. Abstract To generate high and stable spin-polarized electron beams by field-emission for applications to electron microscopy and spectroscopy, we demonstrated spin-polarized field-emitted electrons from a Cr thin film deposited on W 〈 0 0 1 〉 tips at room temperature without an external magnetic field. A spin polarization of the field-emitted electrons of 35–50% was achieved when the Cr thickness was higher than 20 nm. In addition, a maximum spin polarization of 50% was achieved, consistent with the value for a Cr(0 0 1) surface expected by first-principles calculations. The polarization direction was also stable for 3 h with no abrupt change. This study indicates that antiferromagnetic Cr is proper cathode material for a field emitter than other ferromagnetic materials with an instability limited by superparamagnetic state. [ABSTRACT FROM AUTHOR]

In this work, we have used the first-principle calculations approach based on spin-polarized density functional theory, and predicted the half-metallic behavior of In1-xMnxSb alloys (x = 0:25, 0.50, 0.75). The structural, electronic and magnetic properties of these ternary cubic crystals have been investigated. The electronic exchangecorrelation energy has been characterized by the generalized gradient approximation with the WC functional improved by the Tran-Blaha modified Becke-Johnson exchange potential approximation. The calculated formation energy indicates that In1-xMnxSb compounds (at all compositions) are thermodynamically stable, and can be synthesized. Our calculated structural parameters are in good accordance with the available theoretical and experimental data. The ternary alloys In1-xMnxSb are half-metallic ferromagnets with a spin polarization at the Fermi level of 100%. Our investigation shows an antiferromagnetic interaction between Mn-Sb and Mn-In, the total magnetic moment is equal to 4:00 μB for all studied structures. These materials are half-metallic ferromagnets, and thus may be potential candidates for spintronics applications. [ABSTRACT FROM AUTHOR]

Spin-polarized scanning tunneling microscopy (SP-STM) measures magnetoresistance with atomic resolution. While various methods for achieving SP probes have been developed, each is limited with respect to fabrication, performance, and operating conditions. In this study, we present the fabrication and use of SP-STM tips made from commercially available antiferromagnetic Mn88Ni12 foils. The tips are intrinsically SP, which is attractive for exploring magnetic phenomena in the zero field limit. The tip material is relatively ductile, is straightforward to etch, and has a Néel temperature exceeding 300 K. We benchmark the topographic and spectroscopic performance of our tips and demonstrate their spin sensitivity by measuring the two-state switching of holmium single atom magnets on MgO/Ag(100). [ABSTRACT FROM AUTHOR]

Highlights • Surface antiferromagnetism of the Cr(0 0 1) c(2 × 2) surface. • Quantitative determination of the antiferromagnetic coupling angles. • New spin quantization axes along the [1 1 0] of Cr(0 0 1). Abstract We present spin-polarized scanning tunneling microscopy results for 8 micrometer thick, chromium (0 0 1)-oriented thin films deposited using molecular beam epitaxy on MgO(0 0 1) substrates, achieving a smooth, atomically-stepped staircase morphology. The c(2 × 2) surface structure of the Cr(0 0 1) surface was found via atomically-resolved scanning tunneling microscopy images and dI/dV spectroscopy. A practical method of interpreting spin-polarized scanning tunneling microscopy dI/dV images was developed and applied to the c(2 × 2) Cr(0 0 1) surface structure. A 180° spin reversal between atomic layers, characteristic of a topological, layer-wise antiferromagnetic spin structure, was quantitatively verified. In addition, the spin anisotropy directions for 3 different antiferromagnetic, atomic staircase domains occurring on the c(2 × 2) surface were quantitatively determined to coincide with the [1 0 0], [0 1 0], and [1 1 0] crystallographic axes of chromium. [ABSTRACT FROM AUTHOR]

• Superconducting NbN has low spin–orbit coupling and makes a good candidate to perform meservey-tedrow measurements. • Using the robust surface oxide, tunnel junctions on NbN can be fabricated using a facile process without lithography. • Due to the high t c of NbN (∼16.5 K), one can perform the spin polarization measurement of ferromagnets at temperatures at high as 1.57 K. We report a two-step process for the fabrication of superconductor-insulator-normal metal tunnel junctions using NbN as the superconducting electrode and its surface oxide as the insulating tunnel barrier, and investigate its efficacy in measuring spin-polarisation of ferromagnets using the Meservey-Tedrow technique. We observe that for NbN film thickness below 10 nm, under the application of parallel magnetic field, the superconducting density of states show clear "Zeeman" splitting into spin-up and spin-down sub-bands. Tunnelling measurements on devices where ferromagnetic Co is used as the normal electrode shows that these devices can be used to measure spin polarisation of a ferromagnet at temperatures up to 1.6 K. The simplicity of our fabrication process makes NbN a very attractive candidate for spin polarisation measurements. Some limitations of this process are also discussed. [ABSTRACT FROM AUTHOR]

The structural, electronic, and magnetic properties of (ZnO) 12 clusters doped with Cr atoms have been investigated by using spin-polarized first-principles calculations. The exohedral a3 isomer is favorable than endohedral a2 isomer. The isomer a1 and a5 respectively have the narrowest and biggest gap between highest unoccupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO) of 0.473 and 1.291 eV among these five monodoped isomers. The magnetic moment may be related to the local environment around the Cr atom that the a2 isomer whose total magnetic moment is 6 μ B while the other monodoped isomers which all isomers have nearly total magnetic moments 4 μ B . For Cr-doped (ZnO) 12 on a1 or a3 isomer, the DOS of spin-up channel cross the Fermi level E F showing a finite magnitude near the Fermi level which might be useful for half metallic character. For the bidoped cases, the exohedral isomers are found to be most favorable. Including all bipoed isomers of substitutional, exohedral and endohedral bidoped clusters, the total magnetic moment of the ferromagnetic (antiferromagnetic) state is 8 (0) μ B and the HOMO-LUMO gap of antiferromagnetic state is slightly larger than that of ferromagnetic state. The magnetic coupling between the Cr atoms in bidoped configurations is mainly governed by the competition between direct Cr and Cr atoms antiferromagnetic interaction and the ferromagnetic interaction between two Cr atoms via O atom due to strong p-d hybridization. Most importantly, we show that the exohedral bidoped (ZnO) 12 clusters favor the ferromagnetic state, which may have the future applications in spin-dependent magneto-optical and magneto-electrical devices. [ABSTRACT FROM AUTHOR]

Fine-tuning magnetic states by understanding topological frustration inducing magnetic mechanism should allow greater flexibility for the design of graphene-based spintronics. Based on first-principles calculations, it is predicted that bowtie-shaped graphene nanoflake (GNF) is of spin-polarized ground state exhibiting antiferromagnetic (AFM) ordering between two individual triangular GNFs. It is demonstrated that strength of antiferromagnetic coupling of both symmetric and asymmetric bowtie-shaped GNF displays strong zero-energy-state-orientated behavior due to non-trivial nature of topological frustration, with implications for designing graphene nanostructures with predefined magnetic states. It also proposes a specific example of structures that can serve as nanoscale molecular logic gates composed by asymmetric bowtie-shaped GNFs units, which augment the special antiferromagnetic function through structural configuration of multi-bowtie-shaped GNFs. [ABSTRACT FROM AUTHOR]

We have investigated topological confinement effects of edge potentials on gapless edge states in zigzag-edge graphene nanoribbons (ZGNRs) under a staggered bulk potential. A variety of gapless edge states were predicted with the concept of topological confinement effect alone, which was confirmed by using tight-binding model calculations. Half-metallicity of ZGNR, which has been semiclassically described, was revealed to fundamentally result from a topological confinement effect. Edge potentials were found to allow an infinitesimal staggered bulk potential to result in gapless edge states, regardless of the ribbon width. A uniform or staggered potential applied to the boundary region narrower than a critical width was found to play a role of the edge potentials, and the critical width was estimated. [ABSTRACT FROM AUTHOR]

This study focuses on new diluted magnetic semiconductors that have good characteristics. The chemical compound we use in this paper is Mg 1-x Cr x S (x = 0,0, 0.125, 0.25, 0.50, 0.75) at the ferromagnetic rock salt phase, We used the linearized augmented plane wave method implemented in the wien2k package to simulate compound properties and adopted the WC-GGA approximation to calculate structural and elastic properties and the Tb-mBJ approximation (Tran-Blaha modified Becke-Johnson potential) to calculate electronic, and optical properties. The results obtained prove that the ferromagnetic (FM) phase is more stable than the antiferromagnetic (AFM) and nonmagnetic (NM) phases, the energy band of all ternary compounds Mg 1-x Cr x S has been shown to be half-metals with a 100% spin polarization at the Fermi level (E F) and total magnetic moment values equal to 4 μB. The study reported that the elastic properties of Mg 1-x Cr x S (x = 0.125, 0.25, 0.50, 0.75) compounds are mechanically stable with high mechanical anisotropy. The optical spectra of ternary compounds Mg 1-x Cr x S (x = 0.125, 0.25, 0.50, 0.75) are distinguished from those of MgS by the appearance of additional absorption at low energy. The compounds are dispersive media that show strong absorption in the ultraviolet radiation region observed on the α (ω) curve. [ABSTRACT FROM AUTHOR]

The interfacial interaction between graphene and ferromagnetic substrate is known to bring additional controls to the intrinsic properties of graphene, in addition to inducing some novel properties to the system which may have potential application in spintronics. In this work the spin-polarized electronic structures across the graphene–ferromagnet interface has been investigated using first principles density functional theory calculation as it is implemented on Vienna ab-initio simulation package (VASP). The electronic and magnetic properties of the interface have also been investigated. The ferromagnet substrate was represented by N i (111) and C o (111) surfaces due to their structural resemblance to graphene. The study reveals that the ferromagnet layers adjacent to the interface show a transition of spin orientation from in plane to out of plane. The critical thickness of the slab which yields the maximum shifting of the spin orientation of the ferromagnet layers is also determined. The strong hybridization between different orbitals of graphene and ferromagnet significantly affects the electronic and magnetic properties of the interface. Reduction on the local magnetic moments of the ferromagnet layers adjacent to the interface and the induced spin polarization on the graphene layer were also observed which is due to the impacts of the hybridization. This work will provide important information which can be used for efficient design of interfaces for graphene-based spintronics. [ABSTRACT FROM AUTHOR]

Comprehensive spin-polarized calculations were performed for the recently synthesized antiferromagnetic CaCoSO single crystal based on the full-potential method plus Hubbard Hamiltonian. The experimental lattice parameters of the CaCoSO single crystal were optimized and the experimental atomic positions were relaxed so as to minimize the forces acting on the atoms. The calculations show that the spin-up (-down) channels exhibit a direct energy band gap Γ v - Γ c (K v -K c ) of about 2.187 (1.187) eV and the spin-polarized antiferromagnetic CaCoSO single crystal exhibits an indirect energy band gap (Γ v - K c ) of about 0.4 eV. The obtained magnetic moment of 3d electrons within the Co sphere (2.56 μ B) is the highest among the others and agrees well with the measured ones (2.75 μ B). Further, the charge density distribution of the spin-polarized valence electrons for the spin-up and spin-down channels were investigated in two crystallographic planes. The calculated bond lengths and angles show good agreement with the measured ones. [ABSTRACT FROM AUTHOR]

We have investigated the adsorption sites and the electronic structure correlated with the magnetic properties of ultrathin Fe films on W(110) system using spin-polarized calculations within the density-functional approach with generalized gradient approximation by the pseudopotential plane-wave code. For one Fe monolayer (ML) on W(110) system the Fe atoms prefer to bind on the bridge adsorption sites of the W(110) surface, with an inward relaxation of 12.68%. The top and diagonal bridge sites investigated are energetically less favorable. We have shown that intermixing between Fe and W is unlikely: the surface ordered Fe-W alloy is unstable against the 1-ML Fe on W(110). While the control of oxygen element is known to be an important key to a perfect growth of Fe on W(110), its possible contamination is checked. Performing spin polarized calculations with the optimized geometry, the induced magnetic moments on W subsurface are obtained: the W atoms are always antiferromagnetically coupled to the Fe atoms, one exception being the case of the antiferromagnetic Fe surface where, due to frustration, the induced polarization on the W atoms is zero. The bridge site is the lower adsorption energy one for O2 molecular bonding perpendicular to the surface. In the case of O2 bonding parallel and oblique to the surface, it is always dissociated into two O atoms on Fe/W(110) surface through geometry optimization, for all considered sites. [ABSTRACT FROM AUTHOR]

An incommensurate spin-density wave (Q phase) confined inside the superconducting state at high basal plane magnetic field is an unique property of the heavy-fermion metal CeCoIn5. The neutron scattering experiments and the theoretical studies point out that this state come out from the soft mode condensation of magnetic resonance excitations. We show that the fixation of direction of antiferromagnetic modulations by a magnetic field reported by Gerber et al. [Nat. Phys. 10, 126 (2014)], is explained by spin-orbit coupling. This result, obtained on the basis of quite general phenomenological arguments, is supported by the microscopic derivation of the Xzz susceptibility dependence on the mutual orientation of the basal plane magnetic field and the direction of modulation of spin polarization in a multiband metal. [ABSTRACT FROM AUTHOR]

The antiferromagnetic (AFM) CrI 3 bilayer is a particularly interesting representative of van der Waals 2D semiconductors, which are currently being studied for their magnetism and for their potential in spintronics. Using ab initio density-functional theory calculations, we investigate the spin texture in momentum space of the states of the (doubly degenerate) highest valence band of the AFM CrI 3 bilayer with Cr-spin moments perpendicular to the layers. We find the existence, in the main central part of the Brillouin zone, of a Rashba in-plane spin texture of opposite signs on the two layers, resulting from the intrinsic local electric fields acting on each layer. To study the layer segregation of the wavefunctions, we apply a small electric field that splits the degenerate states according to their layer occupancy. We find that the wavefunctions of the highest valence band are layer-segregated, belonging to only one of the two layers with opposite in-plane spin textures, and the segregation occurs over nearly the whole Brillouin zone. The corresponding layer locking of the in-plane-canted spin is related to the separation in energy of the highest AFM band from the rest of the valence bands. We explain how the band interactions destroy the layer locking at the K , K ′ , and Γ points. Furthermore, we compare the layer locking of the in-plane-canted spin in our AFM bilayer system with the hidden spin polarization in centrosymmetric nonmagnetic materials, pointing out the differences in segregation mechanisms and their consequences for the layer locking. We note that a similar Rashba effect with layer locking of in-plane-canted spin could occur in other van der Waals AFM bilayers with strong spin–orbit coupling and an isolated energy band. [Display omitted] • k -space spin-texture is studied for antiferromagnetic chromium-tri-halide bilayer. • Existence of Rashba-type spin textures with opposite spin canting on two monolayers. • Segregation of wavefunctions of highest valence band on one of the two layers. • Layer locking is related to separation in energy of the highest AFM valence band. [ABSTRACT FROM AUTHOR]

Because of this lattice mismatch, the tetragonal FM Mn 3 Ge grown along c -axis on STO will definitely be stretched at the interface. The thickness dependent double-phase Mn 3 Ge films with large magnetic anisotropy and robust anomalous Hall effect were obtained. [Display omitted] • The high quality perpendicularly magnetized Mn 3 Ge films were grown by magnetron sputtering. • XRD shows that hexagonal antiferromagnetic Mn 3 Ge is mixed with tetragonal ferromagnetic Mn 3 Ge. • The thickness dependent double-phase Mn 3 Ge films with large magnetic anisotropy and robust anomalous Hall effect were obtained. Mn 3 Ge, a typical member of the Heusler family, has a high spin polarization and large spin Hall angle, making it a potential material for spintronic devices. Regarded as a topological Weyl semi-metal, Mn 3 Ge could be applied in topological spintronics owing to its special Fermi-arc-type surface states and various spin transport properties. In this study, we grew high-quality perpendicularly magnetized Mn 3 Gefilms through magnetron sputtering. X-ray diffraction (XRD) showed that hexagonal antiferromagnetic Mn 3 Ge was mixed with tetragonal ferromagnetic Mn 3 Ge. Thickness-dependent double-phase Mn 3 Ge films with large magnetic anisotropy and robust anomalous Hall effect (AHE) were obtained. The triangular spin structure of hexagonal Mn 3 Ge enhances the AHE; however, it shrinks the coercivity of the tetragonal ferromagnetic property. This manipulation of coexisting multi-phases comes from the strain of the substrate during growth, achieved by controlling the film thickness. Structural, magnetic, and transport measurements demonstrated stress modulation of the defect pinning, magnetic anisotropy, and spin transport properties. The coexistence of antiferromagnetic and ferromagnetic Mn 3 Ge provides the possibility of a new generation of Mn 3 X-based devices for applications in spin-torque memories. [ABSTRACT FROM AUTHOR]

The electronic structures of ε-phase of solid oxygen (O2)4 are studied within the framework of densityfunctional theory. The intriguing molecule has been known to have magnetic properties at room temperature by applying pressure. Nevertheless, until now there was no evidence of band structure studied in the antiferromagnetic behaviour of (O2)4. We report a comparison study for spin and non-spin polarization orbital which suggests that this ferromagnetic configuration of (O2)4 could not be seen experimentally, and antiferromagnetic configuration of (O2)4 was seen at higher pressure of about 10 GPa. The antiferromagnetic state transforms into the superconducting state as the sample temperature decreases. The results can serve as a useful approximation in studying general features of the electronic structure. The (O2)4 clusters are reported in the Raman study, having significant absorption at 1516 cm-1 below infrared region. [ABSTRACT FROM AUTHOR]

We study spin-dependent electron transport properties of zigzag silicene nanoribbons in the presence of anti-ferromagnetic exchange field using a nonequilibrium Green׳s function method. Applying a transverse electric field, spin splitting can take place and the silicene nanoribbon can work as a spin filter. The spin polarization is calculated and it is shown that the spin filtering is perfect and the spin states of electrons are fully coherent. The spin direction of transmitted electrons through the silicene filter can be easily controlled by changing the transverse electric field direction. Using Hubbard model, we take into account the electron–electron interaction and we find that although this interaction causes some changes in the electron conductance, it has no destructive effect on spin filtering properties. The effect of a single vacancy on electron transport is also investigated and it is found that, the vacancy causes to decrease the electron conductance; however, the spin-dependent properties remain the same. The vacancy in the near of the edges of nanoribbon has less destructive effect on electron conductance than that in the middle. [ABSTRACT FROM AUTHOR]

Molecular semiconductors may exhibit antiferromagnetic correlations well below room temperature. Although inorganic antiferromagnetic layers may exchange bias single-molecule magnets, the reciprocal effect of an antiferromagnetic molecular layer magnetically pinning an inorganic ferromagnetic layer through exchange bias has so far not been observed. We report on the magnetic interplay, extending beyond the interface, between a cobalt ferromagnetic layer and a paramagnetic organic manganese phthalocyanine (MnPc) layer. These ferromagnetic/organic interfaces are called spinterfaces because spin polarization arises on them. The robust magnetism of the Co/MnPc spinterface stabilizes antiferromagnetic ordering at room temperature within subsequent MnPc monolayers away from the interface. The inferred magnetic coupling strength is much larger than that found in similar bulk, thin or ultrathin systems. In addition, at lower temperature, the antiferromagnetic MnPc layer induces an exchange bias on the Co film, which is magnetically pinned. These findings create new routes towards designing organic spintronic devices. [ABSTRACT FROM AUTHOR]

Perpendicularly magnetized flat thin films of antiperovskite Mn67Ga24N9 were grown on an MgO(001) substrate by reactive sputtering using an argon/1% nitrogen gas mixture and a Mn70Ga30 target. The films showed a saturation magnetization of 80-100kA/m, an effective perpendicular magnetic anisotropy (PMA) energy of 0.1-0.2MJ/m³, and a Curie temperature of 660-740K. Upon increasing the N composition, the films transformed from ferromagnetic to antiferromagnetic as expected in the stoichiometric Mn3 GaN phase. Point contact Andreev reflection spectroscopy revealed that the ferromagnetic MnGaN has a current spin polarization of 57%, which is comparable to D022-MnGa. These findings suggest that MnGaN is a promising PMA layer for future spintronics devices. [ABSTRACT FROM AUTHOR]

Antiferromagnets produce no stray field, and therefore, a tip electrode made of antiferromagnetic material has been considered to be the most suitable choice to measure such as magnetoresistance (MR) through single isolated magnetic nanoparticles, molecules, and ultrathin films. Spin polarizations (P) of antiferromagnetic 3-nm, 6-nm, and annealed 3-nm Mn films grown on W tips with a bcc(110) apex as well as bulk-NiMn tips were obtained at 300 K by measuring MR in ultra-high vacuum by means of spin-polarized scanning tunneling microscopy using a layerwise antiferro-magnetically stacking bct-Mn(001) film electrode. The Mn-coated tips with coverages of 3 and 6nm exhibited P values of 1 ± 1% and 3 ± 2%, respectively, which tips likely contain α- or strained Mn. With a thermal assist, the crystalline quality and the magnetic stability of the film could increase. The annealed tip exhibited P = 9 ± 2%. The bulk-NiMn tips exhibit spin polarizations of 0 or 6 ± 2% probably depending on the chemical species (Mn or Ni) present at the apex of the tip. Fe-coated W tips were used to estimate the bct-Mn(001) film spin polarization. [ABSTRACT FROM AUTHOR]

Abstract: We performed a spin polarized density-function theory study of the stabilities, electronic and magnetic properties of zigzag silicene nanoribbons (ZSiNRs) substitutionally doped with a single N or B atom located at various sites ranging from edge to center of the ribbon. From minimization of the formation energy, it is found that the substitutional doping is favorable at edge of the ribbon. A single N or B atom substitution one edge Si atom of ZSiNRs can greatly suppress the spin-polarizations of the impurity atom site and its vicinity region, and leads to a transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state, which is attributed to the splitting of the original spin degenerate edge bands. A single N atom doped ZSiNRs still keep semiconductor property but a single B atom doped ZSiNRs exhibit a half-metallic character. Our results reveal that substitution doped ZSiNRs have potential applications in Si-based nanoelectronics, such as field effect transisitors (FETs), negative differential resistance (NDR) and spin filter (SF) devices. [Copyright &y& Elsevier]

We investigate the properties of antiferromagnetic spin-S ladders with the help of local Berry phases defined by imposing a twist on one or a few local bonds. In gapped systems with time-reversal symmetry, these Berry phases are quantized, hence able in principle to characterize different phases. In the case of a fully frustrated ladder where the total spin on a rung is a conserved quantity that changes abruptly upon increasing the rung coupling, we show that two Berry phases are relevant to detect such phase transitions: the rung Berry phase defined by imposing a twist on one rung coupling, and the twist Berry phase defined by twisting the boundary conditions along the legs. In the case of nonfrustrated ladders, we have followed the fate of both Berry phases when interpolating between standard ladders and dimerized spin chains, with the surprising conclusion that, at least far enough from dimerized chains, they define different domains in parameter space. A careful investigation of the spin gap and of edge states shows that a change of twist Berry phase is associated with a quantum phase transition at which the bulk gap closes, and at which, with appropriate boundary conditions, edge states appear or disappear, while a change of rung Berry phase is not necessarily associated with a quantum phase transition. The difference is particularly acute for regular ladders, in which the twist Berry phase does not change at all upon increasing the rung coupling from zero to infinity while the rung Berry phase changes 2S times. By analogy with the fully frustrated ladder, these changes are interpreted as crossovers between domains in which the rungs are in different states of total spin from 0 in the strong rung limit to 2S in the weak rung limit. This interpretation is further supported by the observation that these crossovers turn into real phase transitions as a function of rung coupling if one rung is strongly ferromagnetic, or equivalently if one rung is replaced by a spin 2S impurity. [ABSTRACT FROM AUTHOR]

The magnetism of a metallic two-dimensional triangular antiferromagnetic (AF) compound, Ag2CrO2, has been investigated by muon-spin rotation and relaxation (μ+SR) using a powder sample in the temperature range between 1.8 and 40 K. Below TN = 24 K, a muon-spin precession signal was clearly observed in the zero-field spectrum, indicating the formation of static AF order. It was also found that the internal field is temperature independent except for in the vicinity of TN, as in the case for the susceptibility versus temperature curve. This suggests that the AF transition is induced by a first-order structural phase transition at TN. Combining the μ+SR result with the prediction for muon sites in the lattice by first-principles calculations, a partially disordered AF state was found to be the most reasonable spin structure for Ag2CrO2. [ABSTRACT FROM AUTHOR]

Magnetic exchange force microscopy (MExFM) is one of the most important methods to investigate the spin structure of magnetic surfaces. However, a deep understanding of the measured spin contrast and the spin-dependent forces is missing. For the prototypical antiferromagnetic MnO(001) and NiO(001) surfaces probed by ferromagnetic Fe tips we demonstrate by means of spin-polarized density functional theory that the differences in the tip-surface interaction are due to the distance-dependent occupation of the transition-metal 3d states. While agreement is achieved with recent MExFM measurements of NiO(001), we predict opposite spin-contrast for MnO(001). [ABSTRACT FROM AUTHOR]

In this work we explore how a two-stranded magnetic ladder with vanishing net magnetization can be utilized to generate polarized spin current from a completely unpolarized one. Considering three different types (A-, C- and G-type) of antiferromagnetic ladders within a tight-binding framework, we make a comparative study to find the best suitable ladder for spin filtration. Our analysis can be implemented to design efficient spintronic devices with the help of antiferromagnetic materials, circumventing the use of conventional ferromagnetic systems. • Spin filtration in an antiferromagnetic ladder is studied. • Condition of getting spin polarization is achieved analytically. • Results can be extended to any magnetic system with zero net magnetization. • Effect of spin flipping is explored. • Experimental realizations are discussed. [ABSTRACT FROM AUTHOR]

We present experimental observations of coherent spin-population oscillations in a cold thermal, Bose gas of spin-1 23Na atoms. The population oscillations in a multi-spatial-mode thermal gas have the same behavior as those observed in a single-spatial-mode antiferromagnetic spinor Bose-Einstein condensate. We demonstrate this by showing that the two situations are described by the same dynamical equations, with a factor of 2 change in the spin-dependent interaction coefficient, which results from the change to particles with distinguishable momentum states in the thermal gas. We compare this theory to the measured spin population evolution after times up to a few hundreds of ms, finding quantitative agreement with the amplitude and period. We also measure the damping time of the oscillations as a function of magnetic field. [ABSTRACT FROM AUTHOR]

We propose a scheme of band engineering by means of staggered electric potential, antiferromagnetic exchange field and intrinsic spin-orbit coupling for electrons on a honeycomb lattice. With fine control on the degrees of freedom of spin, sublattice and valley, one can achieve a topological state with simultaneous non-zero charge and spin Chern numbers. With first principles calculations, we confirm that the scheme can be realized by material modification in perovskite G-type antiferromagnetic insulators grown along the [111] direction, where Dirac electrons from d orbits are achieved on an atomic sheet of a buckled honeycomb lattice. In a finite sample, this state provides a spin-polarized quantum edge current, robust to both non-magnetic and magnetic defects, with the spin polarization reversible by electric field, and is thus ideal for spintronics applications. [ABSTRACT FROM AUTHOR]

The unique properties of synchrotron radiation, such as broad energy spectrum, variable light polarization, and flexible time structure, have made it an enormously powerful tool in the study of magnetic phenomena and materials. The refinement of experimental techniques has led to many new research opportunities, keeping up with the challenges put up by modern magnetism research. In this contribution, we review some of the recent developments in the application of synchrotron radiation and particularly soft X-rays to current problems in magnetism, and we discuss future perspectives. [ABSTRACT FROM AUTHOR]