Potential Applications In Spintronics Research Articles

High-throughput inverse design and Bayesian optimization of functionalities: spin splitting in two-dimensional compounds

The development of spintronic devices demands the existence of materials with some kind of spin splitting (SS). In this Data Descriptor, we build a database of ab initio calculated SS in 2D materials. More than that, we propose a workflow for materials design integrating an inverse design approach and a Bayesian inference optimization. We use the prediction of SS prototypes for spintronic applications as an illustrative example of the proposed workflow. The prediction process starts with the establishment of the design principles (the physical mechanism behind the target properties), that are used as filters for materials screening, and followed by density functional theory (DFT) calculations. Applying this process to the C2DB database, we identify and classify 358 2D materials according to SS type at the valence and/or conduction bands. The Bayesian optimization captures trends that are used for the rationalized design of 2D materials with the ideal conditions of band gap and SS for potential spintronics applications. Our workflow can be applied to any other material property.

Manipulating the metal-to-insulator transition and magnetic properties in manganite thin films via epitaxial strain

Strain engineering of epitaxial transition metal oxide heterostructures offers an intriguing opportunity to control electronic structures by modifying the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, we demonstrate that the electronic structure, magnetic and transport properties of ${\mathrm{La}}_{0.9}{\mathrm{Ba}}_{0.1}{\mathrm{MnO}}_{3}$ thin films can be effectively controlled by epitaxial strain. Spectroscopic studies and first-principles calculations reveal that the orbital occupancy in Mn ${e}_{g}$ orbitals can be switched from the ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbital to the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbital by varying the strain from compressive to tensile. The change of orbital occupancy associated with Mn $3d$-O $2p$ hybridization leads to dramatic modulation of the magnetic and electronic properties of strained ${\mathrm{La}}_{0.9}{\mathrm{Ba}}_{0.1}{\mathrm{MnO}}_{3}$ thin films. Under moderate tensile strain, an emergent ferromagnetic insulating state with an enhanced ferromagnetic Curie temperature of 215 K is achieved. These findings not only deepen our understanding of electronic structures, magnetic and transport properties in the ${\mathrm{La}}_{0.9}{\mathrm{Ba}}_{0.1}{\mathrm{MnO}}_{3}$ system, but also demonstrate the use of epitaxial strain as an effective knob to tune the electronic structures and related physical properties for potential spintronic device applications.

Rational Design of Heteroanionic Two-Dimensional Materials with Emerging Topological, Magnetic, and Dielectric Properties.

Designing and tuning the physical properties of two-dimensional (2D) materials at the atomic level are crucial to the development of 2D technologies. Here, we introduce heteroanions into metal-centered octahedral structural units of a 2D crystal breaking the Oh symmetry, together with the synergistic effect of anions' electrons and electronegativity, to realize ternary 2D materials with emerging topological, magnetic, and dielectric properties. Using an intrinsic heteroanionic van der Waals layered material, VOCl, as a prototype, 20 2D monolayers VXY (X = B, C, N, O, or F; Y = F, Cl, Br, or I) are obtained and investigated by means of first-principles calculations. The anion engineering in this family significantly reshapes the electronic properties of VOCl, leading to nonmagnetic topological insulators with nontrivial edge states in VCY, ferromagnetic half-semimetals with a nodal ring around the Fermi energy in VNY, and insulators with dielectric constants in VOY higher than that of h-BN. This work demonstrates the rationality and validity of the design strategy of multiple-anion engineering to achieve superior properties in the 2D monolayers with potential application in electronics and spintronics.

Tunable electronic and magnetic properties of two-dimensional magnetic semiconductor VIBr[formula omitted

The recent discovery of two-dimensional (2D) magnetic materials have attracted interest of the scientific community due to their potential applications in spintronics. In this work, we demonstrate by using density functional theory calculations that VIBr2 is a magnetic semiconductor. To tune the electronic and magnetic properties, we consider the application of biaxial strain (η), electric field (Ez) and combination of both. We find the phase transition from semiconductor → half-metal → metal, with ferromagnetic and antiferromagnetic ground states under different excitations. The maximum enhancement in Curie temperature is ∼1126% under application of external stimuli. The presence of various unique properties predicted by our detailed calculations give evidence that VIBr2 can be a promising candidate for future spintronic applications.

Visualizing Emergent Magnetic Flux of Antiskyrmions in Mn1.4PtSn Magnet

AbstractTopologically protected spin textures, such as magnetic skyrmions, have attracted considerable attention owing to their emergent electromagnetic phenomena and potential applications in spintronics. The antiskyrmion, a new member of the skyrmion family in the nanoscale dimension, consists of alternating Néel‐ and Bloch‐type boundary walls; it has already been discovered in non‐centrosymmetric magnets with D2d/S4 symmetry. However, its complex spin textures and unique magnetic‐charge‐induced emergent field have not been explicitly visualized thus far. Here, state‐of‐the‐art off‐axis electron holography is employed to directly resolve the antiskyrmions in a non‐centrosymmetric Heusler magnet Mn1.4PtSn with D2d symmetry. The magnetic flux distribution inside and outside the antiskyrmion is clearly imaged, indicating the emergent magnetic field induced by the broken cylindrical symmetry. More importantly, the closed emergent flux between adjacent antiskyrmions is revealed, indicating the antiskyrmion‐antiskyrmion interactions (a different mechanism compared to that of conventional skyrmions). These findings provide a clear and deep insight into the intrinsic magnetic flux configuration in the antiskyrmion‐hosted magnets, thus paving the way for the manipulation of antiskyrmions in the future.

Prediction of spin-dependent electronic structures of 3d transition metals doped Hittorf's violet phosphorene towards spintronics

Modulation of spin-dependent properties in semiconductor is of importance in exploring the potential application in spintronics. Here, we theoretically investigated the structural deformation, electronic characters, and magnetic properties of the single-layered Hittorf's violet phosphorene nanosheet with 3 d transition metal atoms (ranging from Sc to Ni) doping and under external electric field. The electronic band structures and magnetic properties was found to be obviously modulated by the dopants: the existence of a large spin splitting of the dopant 3 d states tailors the semiconducting phosphorene into simple magnetic semiconductor or bipolar magnetic semiconductor, except for the case of Sc. The application of an appropriate electric field to V-doped system could induce a transition from bipolar magnetic semiconductor to half metal with the carriers fully spin-polarized in alternative spin channel. Moreover, Hittorf's violet phosphorene-based field-effect transistor was proposed with the aim of realizing gate-voltage control on the carriers' spin orientation. Our findings pointed out the possibilities for realizing spin-dependent field-effect transistor in doped Hittorf's violet phosphorene nanosheet and opened a window for the burgeoning field of multifunctional 2D nanoelectronics and spintronics devices. • Ranging from Ti to Ni dopants can behave (bipolar) magnetic semiconductors. • Sc-doped Hittorfene is a nonmagnetic semiconductor. • The application of the electric field to V-doped Hittorfene can induce half metal transition. • The reversed carriers' spin orientation would be potential for spintronic devices.

Chemical Vapor Deposition of Ferrimagnetic Fe3O4 Thin Films

Ultrathin magnetic materials with room-temperature ferromagnetism/ferrimagnetism hold great potential in spintronic applications. In this work, we report the successful controllable growth of Fe3O4 thin films using a facile chemical vapor deposition method. Room-temperature ferrimagnetism was maintained in the as-grown Fe3O4 thin films down to 4 nm. Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis were conducted to reveal the structure and quality of the Fe3O4 film. Magnetization measurement showed ferrimagnetic hysteresis loops in all Fe3O4 thin films. A saturation magnetization of 752 emu/cm3 was observed for the 4 nm Fe3O4 film, which was higher than that of bulk Fe3O4 materials (480 emu/cm3). Additionally, the Verwey transition at ~120 K was visible for the Fe3O4 thin films. This work provides an alternative method of synthesizing ferrimagnetic ultrathin films for electronic, spintronic, and memory device applications.

Coexistence of multiple Weyl fermions and quantum anomalous Hall effect in 2D half-metallic Cr2NT2

Topological state in two-dimensional (2D) magnetic system has attracted widespread attention due to its potential application in spintronics and quantum computing fields. As a novel topological states of matter, Weyl semimetals with multiple topological phases have been studied. However, realizing multiple topological phases in 2D magnetic system and studying their entanglement still face great challenges. In this work, using first-principles calculations, we predict that 2D monolayer Cr2NT2 (T = -OH, -F, =O) has multiple Weyl fermions (WFs) and large spin-down gap. Ferromagnetic ground states of monolayer Cr2NT2meet the dynamic, thermal and mechanical stabilities. Without spin-orbit coupling (SOC), these WPs are fully spin-polarized. When considering SOC, apart from WP3 in Cr2NO2, all WPs are opened the gap, and the chiral edge states are observed in Cr2NT2. In particular, there is a quantum anomalous Hall effect in Cr2NF2. Further, a biaxial strain in the a-b plane leads to the emergence of rich topological phases without SOC. In addtion, an effective four-band tight-binding model is constructed to clarify the origin of WFs in the non-trivial band topology. Finally, we calculate the Berry curvature and abnormal Hall conductivity of Cr2NT2, and find that they are a non-zero energy points around the Fermi level, indicating that monolayer Cr2NT2 are promising candidates for spintronic applications. Therefore, it is necessary to explore 2D magnetic materials with multiple types of WFs and QAH phases.

Half-metallic of non-metal-adsorbed AsP and multifunctional two-dimensional spintronic device of impure AsP from first-principles calculations

Black arsenic phosphorus (b-AsP) monolayer is a new two-dimensional (2D) nano material with medium band gap and ultra-high carrier mobility , which will have broad application prospects in 2D electronic devices. Here the electron and magnetic of non-metallic light atoms adsorbed AsP are studied by density functional theory (DFT). The hollow sites of B and N adsorbed AsP are half-metallic make them a promising spin material. According to the calculation of the hollow site devices of AsP adsorbed by B and N exhibit almost perfect spin filtering effect. In addition, the I–V curve of the device for B-adsorbed AsP shows a significant negative differential resistance effect. The magnetoresistance of N-adsorbed AsP device is as high as 10 3 %. These results indicate that B-adsorbed and N-adsorbed AsP systems have potential applications in spintronics . • Pure arsenic phosphorus can be changed from non-magnetic semiconductor to half-metal by doping B and N at specific sites. • The spin filtration effect of 100% and tunnel maganetoresistance of around 10 3 % can be obtained in B and N adsorbed arsenic phosphorus devices. • The negative differential resistance effect is found in B adsorbed arsenic phosphorus devices.

The skyrmion annihilations induced by local reversal of background field in a skyrmion lattice

The understanding of the creation and annihilation dynamics of a magnetic skyrmion is significant due to its potential applications in information storage and spintronics. Although there have been extensive investigations on the annihilation of isolated skyrmions, topological annihilation in a periodic skyrmion lattice is a more complex process. We report a micromagnetic simulation study about the annihilation process of a two-dimensional (2D) skyrmion triangular lattice triggered by a uniform field H REV of comparable size to the skyrmion, which is opposite to the direction of the background field, revealing two annihilation modes. When the H REV center is within the range of a skyrmion, the neighboring skyrmions annihilate in-situ, while the center is between adjacent skyrmions, an anti-skyrmion is induced in the interstitial region. Both mechanisms tend to experience the intermediate topological vortex or antivortex structure, and the spin system undergoes a long period of relaxation to reach a stable state after the topological charge is stabilized. Our results present a local annihilation scheme that is easy to achieve in a 2D skyrmion lattice and highlight the role of interaction between skyrmions in the transformation between different kinds of topological defects.

π‐Extendedperi‐Acenes: Recent Progress in Synthesis and Characterization

AbstractNanographenes (NGs) with open‐shell character have gained intense attention due to their potential applications in future organic nanoelectronics and spintronics. Among them, NGs bearing a pair of parallel zigzag edges, such as acenes andperi‐acenes (PAs) bestow unique (opto)electronic and magnetic properties owing to their localized non‐bonding π‐state. However, their reactive zigzag edges impart intrinsic instability, leading to the challenging synthesis. The recent development of synthetic strategies provided access to several π‐extended PAs, which were considered unrealistic for decades. Notably, their laterally π‐extended structures of zigzag‐edged graphene nanoribbons was realised via on‐surface synthesis. However, synthesis of π‐extended PAs in solution is still in its infancy, more intensive scientific efforts are needed to surpass the existing challenges regarding stability and solubility. This Review provides an overview of recent progress in the synthesis and characterization of PAs through a bottom‐up synthetic strategy, including on‐surface and solution‐phase chemistry. In addition, views on existing challenges and the future prospects are also provided.

High Curie Temperature Achieved in the Ferromagnetic MnxGe1-x/Si Quantum Dots Grown by Ion Beam Co-Sputtering.

Ferromagnetic semiconductors (FMSs) exhibit great potential in spintronic applications. It is believed that a revolution of microelectronic techniques can take off, once the challenges of FMSs in both the room-temperature stability of the ferromagnetic phase and the compatibility with Si-based technology are overcome. In this article, the MnxGe1−x/Si quantum dots (QDs) with the Curie temperature (TC) higher than the room temperature were grown by ion beam co-sputtering (IBCS). With the Mn doping level increasing, the ripening growth of MnGe QDs occurs due to self-assembly via the Stranski–Krastanov (SK) growth mode. The surface-enhanced Raman scattering effect of Mn sites observed in MnGe QDs are used to reveal the distribution behavior of Mn atoms in QDs and the Si buffer layer. The Curie temperature of MnxGe1−x QDs increases, then slightly decreases with increasing the Mn doping level, and reaches its maximum value of 321 K at the doping level of 0.068. After a low-temperature and short-time annealing, the TC value of Mn0.068Ge0.932 QDs increases from 321 K to 383 K. The higher Ge composition and residual strain in the IBCS grown MnxGe1−x QDs are proposed to be responsible for maintaining the ferromagnetic phase above room temperature.

Monolayer CeI2 : An intrinsic room-temperature ferrovalley semiconductor

Two-dimensional ferrovalley semiconductors with robust room-temperature ferromagnetism and sizable valley polarization hold great prospects for future miniature information storage devices. As a new member of the ferroic family, however, such ferrovalley materials have rarely been reported. By first-principles calculations, we identify that monolayer $\mathrm{Ce}{\mathrm{I}}_{\text{2}}$ is an intrinsic ferromagnetic semiconductor and exhibits excellent ambient stability, strong easy in-plane magnetocrystalline anisotropy, and a high magnetic transition temperature up to 374 K. The ferromagnetism is found to arise from the hybridization of Ce-$4f/5d$ and I-$5p$ orbitals. When monolayer $\mathrm{Ce}{\mathrm{I}}_{\text{2}}$ is magnetized toward the off-plane $z$ direction, a spontaneous valley polarization as large as 208 meV in the top valence band can be achieved due to the simultaneous breaking of both inversion symmetry and time-reversal symmetry, which is further verified by the perturbation theory of spin-orbital coupling. Also, the anomalous valley Hall effect can be observed under an in-plane electrical field due to the robust valley-contrasting Berry curvature. Overall, the combination of intrinsic semiconducting ferromagnetism and spontaneous valley polarization renders monolayer $\mathrm{Ce}{\mathrm{I}}_{\text{2}}$ a compelling room-temperature ferrovalley semiconductor for potential applications in nanoscale spintronics and valleytronics.

Tuning the magnetic and electronic properties of MoI3 monolayer by 3d transition metal doping: A first-principles study

Two-dimensional (2D) materials with intrinsic magnetism have sparked a lot of attention due to their potential applications in spintronics. Recently, monolayer molybdenum triiodide (MoI3), which is a member of the transition metal trihalides (MX3) family, has been predicted to be a stable bipolar ferromagnetic semiconductor (BFMS) with intrinsic magnetism. By means of first-principle calculations based on the GGA + Ueff approach, we modified MoI3 through substitutional doping with 3d transition metal (TM) atoms to improve its spintronic properties. We focused on the study of structural, electronic and magnetic properties of the pristine and 3d TM (TM = Sc, Ti, V, Cr, and Mn) doped MoI3 systems. Our findings reveal that substitutional doping of MoI3 monolayers with Sc and Ti atoms changes their electronic character from a BFMS to a ferromagnetic semiconductor, while V- and Cr-doped MoI3 monolayers result in half semiconducting properties (HSC). More interestingly, the Mn-doped MoI3 monolayer reveals a half-metallic character with enhanced magnetism and sustains these properties even under spin–orbit coupling (SOC). In addition, robust ferromagnetism and high mean-field Curie temperatures were found in all doped systems, especially in the V-doped MoI3 monolayer. By exhibiting these unique electronic and magnetic properties, these TM-doped MoI3 systems could serve as potential candidates for spintronic applications.

Giant interlayer magnetic exchange interaction and charge-spin coupling in a van der Waals magnetic interface driven by p−d coupling

The van der Waals (vdW) heterostructures are a wonderful playground for condensed matter physics, and the recently discovered two-dimensional magnetism renovates this field. In this work, we construct vdW heterostructures composed of $p$- and $d$-magnetic layers, namely carbon-terminated $\mathrm{Si}\mathrm{C}(111)/\mathrm{Cr}{\mathrm{Br}}_{3}$ and hydrogenated graphene (HG)/$\mathrm{Cr}{\mathrm{Br}}_{3}$. By first-principles calculations, strong interlayer magnetic interaction is predicted, as the interlayer exchange energy is up to hundreds of meV, which may originate from the delocalization of magnetic $p$ orbitals in SiC(111) and HG. Moreover, upon transforming the interlayer magnetic order, the electronic structures of the heterostructures vary dramatically, such as the gap can change from 471 to 4 meV. This significant charge-spin coupling can be ascribed to spin-dependent $p\ensuremath{-}d$ orbital coupling across the vdW interface. The $p\ensuremath{-}d$ coupling is turned on/off by switching interlayer magnetic order, and shifts the energy level so that it alters the band gaps. Besides, the magnetic anisotropy of heterostructures also shows dependence on interlayer magnetic order. Our findings provide inspiration to design vdW heterostructures whose electronic structures can be effectively controlled by magnetism, which have potential applications in spintronics.

Efficient Hydrogen Evolution Reaction with Bulk and Nanostructured Mitrofanovite Pt3Te4.

Here, we discuss the key features of electrocatalysis with mitrofanovite (Pt3Te4), a recently discovered mineral with superb performances in hydrogen evolution reaction. Mitrofanovite is a layered topological metal with spin-polarized topological surface states with potential applications for spintronics. However, mitrofanovite is also an exceptional platform for electrocatalysis, with costs of the electrodes suppressed by 47% owing to the partial replacement of Pt with Te. Remarkably, the Tafel slope in nanostructured mitrofanovite is just 33 mV/dec, while reduced mitrofanovite has the same Tafel slope (36 mV/dec) as state-of-the-art electrodes of pure Pt. Mitrofanovite also affords surface stability and robustness to CO poisoning. Accordingly, these findings pave the way for the advent of mitrofanovite for large-scale hydrogen production.

Thickness-dependent topological phase transition and Rashba-like preformed topological surface states of α-Sn(001) thin films on InSb(001)

Topological materials, possessing spin-momentum locked topological surface states (TSS), have attracted much interest due to their potential applications in spintronics. \ensuremath{\alpha}-phase Sn (\ensuremath{\alpha}-Sn), being one of them, displays enriched topological phases via band-gap engineering through a strain or confinement effect. In this work, we investigated the band evolution of in-plane compressively strained \ensuremath{\alpha}-Sn(001) thin films on InSb(001) in a wide range of thickness from 3 bilayers (BL) to 370 BL by combining angle-resolved photoemission spectra and first-principles calculations. Gapped surface states evolved to a linearly dispersive TSS at a critical thickness of 6 BL, indicating that the system undergoes a phase transition from topologically trivial to nontrivial. For films thicker than 30 BL, additional Rashba-like surface states (RSS) were identified. These RSS served as preformed TSS in another strain-induced topological phase transition. In thick films, 370-BL \ensuremath{\alpha}-Sn(001), so as to preclude the confinement effect in thin films, our results were consistent with a Dirac semimetal phase with Dirac nodes located along $\mathrm{\ensuremath{\Gamma}}--Z$. This thickness-dependent band-structure study deepens our understanding of topological phase transitions and the evolution of Dirac states. Furthermore, the coexistence of TSS and RSS in a Dirac semimetal \ensuremath{\alpha}-Sn might significantly enhance the potential for spintronic applications.

Cooling low-dimensional electron systems into the microkelvin regime

Two-dimensional electron gases (2DEGs) with high mobility, engineered in semiconductor heterostructures host a variety of ordered phases arising from strong correlations, which emerge at sufficiently low temperatures. The 2DEG can be further controlled by surface gates to create quasi-one dimensional systems, with potential spintronic applications. Here we address the long-standing challenge of cooling such electrons to below 1 mK, potentially important for identification of topological phases and spin correlated states. The 2DEG device was immersed in liquid 3He, cooled by the nuclear adiabatic demagnetization of copper. The temperature of the 2D electrons was inferred from the electronic noise in a gold wire, connected to the 2DEG by a metallic ohmic contact. With effective screening and filtering, we demonstrate a temperature of 0.9 ± 0.1 mK, with scope for significant further improvement. This platform is a key technological step, paving the way to observing new quantum phenomena, and developing new generations of nanoelectronic devices exploiting correlated electron states.

Significant Improvement in Magnetic and Magnetoelectric Characteristics of (0.95 − x)Ba0.9Ca0.1TiO3-0.05Na0.5Bi0.5TiO3-xCoFe2O4 Ceramics

Multi-functional materials with high magnetic, electrical, and magnetoelectric characteristics play an important role in development of data storage devices. Herein, a multi-phase (0.95-x)Ba0.9Ca0.1TiO3-0.05Na0.5Bi0.5TiO3-xCoFe2O4 ceramics were prepared by two-stage mechanochemical activation technique. The objective of this study is to develop a multifunctional material with improved multiferroic characteristics. The structural analysis by Rietveld method shows the presence of heterogeneous structure without any impurity phase. The incorporation of CoFe2O4 (CFO) in 0.95Ba0.9Ca0.1TiO3-0.05Na0.5Bi0.5TiO3 (BCT-NBT) has resulted in significant improvement in magnetic and magnetoelectric characteristics without significantly hampering the electrical properties. The sample with x = 0.11 has shown high saturation magnetization of 8.26 emu/g along with moderately high magnetoelectric coefficient of 5.411 mV/cm.Oe. In addition to this, the energy storage performance of all the studied samples have also been investigated and the optimized sample x = 0.11 presents a large discharge energy density of 2.249 J/cm3 and moderately high energy efficiency of 63.8% at 388 kV/cm. The results obtained in the present work suggest a significant influence of CFO substitution on the magnetic characteristics of BCT-NBT ceramics, which subsequently indicate their potential applications in spintronics, magnetic memory storage, and electrical energy storage devices.

Modeling and Simulation of High-Performance CrTe Intrinsic Half Metal-Based Spin Valve and Spin Diode

Most of the pristine two-dimensional materials such as graphene, silicene, germanene etc. are non-magnetic in nature and the creation of magnetism in these materials is subjected to the doping, external field, vacancy, strain etc., but their control in the experimental is very difficult. That has motivated the researchers for the exploration of 2D materials like Transition metal chalcogenides (TMC) with intrinsic magnetism. In the present study, the ferromagnetism of the two-dimensional Chromium telluride (CrTe) is verified by the spin-dependent density of states. Moreover, taking into consideration the similar crystal structure and comparable lattice constants of Vanadium telluride (VTe) to that of CrTe, we have modelled a three-layer spin valve (CrTe-VTe-CrTe) and a two-layer spin diode (CrTe-VTe), and simulated for spin-dependent transport characteristics. The performance parameters like spin injection efficiency, magnetoresistance, rectification ratio has been calculated to carry out the performance evaluation of the modelled devices. The spin valve displays 100% spin injection efficiency and large magnetoresistance of 3.46 × 108%, a comparative study has been carried out to evaluate the performance of the modelled spin valve. Moreover, the spin diode displays high spin filtering efficiency and good rectification ratio, which suggests the potential spintronic applications of the proposed devices. The spin-dependent transport characteristics have been justified by using spin-dependent transmission spectrum and spin-dependent band structure.