Applications In Spintronic Devices Research Articles

Topological transformation of synthetic ferromagnetic skyrmions: thermal assisted switching of helicity by spin-orbit torque

This study demonstrates the controllable switching of skyrmion helicity using spin-orbit torque, enhanced by thermal effects. Electric current pulses applied to a [Pt/Co]3/Ru/[Co/Pt]3 multilayer stripe drive skyrmions in a direction opposite to the current flow. Continuous pulsing results in an unexpected reversal of skyrmion motion. Micromagnetic simulations reveal that skyrmions in the upper and lower ferromagnetic layers exhibit distinct helicities, forming a hybrid synthetic skyrmion. The helicity switch of this hybrid structure accounts for the motion reversal. This study introduces innovative helicity control methods, advancing spintronic device applications, including data storage and quantum computing based on skyrmion helicity.

Influence of atomic substitution on the structural stability and half-metallicity of Fe2-xCrxCoSi (x = 0 to 1) alloys

Bulk Fe2-xCrxCoSi (x = 0, 0.25, 0.5, 0.75, and 1) Heusler alloys have been prepared by arc melting method. Alloys with 0.0 ≤ x ≤ 0.75 show a highly ordered phase pure XA structure. However, 17 % of an impurity (A15 phase) was detected in the alloy with x = 1. The saturation magnetization (Ms) and Curie temperature (TC) decreased linearly with an increase in Cr content for alloys with x ≤ 0.75. Ms measured at 5 K followed the Slater–Pauling rule for half-metals. Ab initio calculations with the GGA + U approach revealed that spin polarization (P) increased with an increase in Cr and eventually reached 100 % for the alloys with x = 0.5. Though Fe-Co disorder affects P, it is still high (>98 %) for alloys with x ≥ 0.5. Despite the smaller bandgap (0.61 eV) of Fe1.5Cr0.5CoSi than FeCrCoSi (0.91 eV), it has higher Ms, elevated TC, and 100 % P. These factors, coupled with the challenges associated with obtaining phase pure FeCrCoSi alloy, make Fe1.5Cr0.5CoSi a preferred candidate for spintronic device applications.

Manipulating dwell time and spin polarization via δ-doping for electrons in spin-orbit-coupling modulated magnetic nanostructure

With the help of atomic-layer doping technology, we theoretically explore how to use a δ-potential to manipulate a temporal electron-spin splitter (TESS), which is based on a spin-orbit-coupling (SOC) modulated magnetic nanostructure. Due to the SOC, the dwell time still depends on electron spins even if a δ-doping is embedded inside the TESS. Moreover, both the magnitude and sign of spin polarization ratio can be controlled by tuning the weight or position of the δ-doping. Therefore, a structurally manipulable TESS device can be obtained for semiconductor spintronic device applications.

Modulation of ferromagnetism through electron doping in Pd-doped β-Ga2O3

The incorporation of magnetism into semiconductor materials offers promising opportunities for expanding their applications in spintronics. In this study, first-principles calculations are employed to investigate the defect energetics and magnetic properties of Pd-doped β-Ga2O3, where Pd atoms substitute for Ga atoms. The results reveal that Pd substitution at tetrahedrally coordinated Ga sites incurs significantly higher energy, favoring octahedral coordination instead. Under n-type doping conditions, Pd tends to stabilize in a negatively charged state, contributing to its magnetic behavior. A detailed analysis of the interaction between Pd-Pd pairs demonstrates that ferromagnetism can be effectively controlled by tuning the carrier concentration. Specifically, at optimal n-type carrier densities, a pronounced ferromagnetic interaction is observed, while this effect diminishes with further increases in electron concentration. The findings provide valuable insights into the defect structures, charge states, and magnetic properties of Pd-doped β-Ga2O3, offering a pathway to manipulating magnetic behavior in semiconductors via carrier concentration modulation, thus paving the way for future spintronic device applications.

Unconventional Anomalous Hall Effect Driven by Self-Intercalation in Covalent 2D Magnet Cr2Te3.

Covalent 2D magnets such as Cr2Te3, which feature self-intercalated magnetic cations located between monolayers of transition-metal dichalcogenide material, offer a unique platform for controlling magnetic order and spin texture, enabling new potential applications for spintronic devices. Here, it is demonstrated that the unconventional anomalous Hall effect (AHE) in Cr2Te3, characterized by additional humps and dips near the coercive field in AHE hysteresis, originates from an intrinsic mechanism dictated by the self-intercalation. This mechanism is distinctly different from previously proposed mechanisms such as topological Hall effect, or two-channel AHE arising from spatial inhomogeneities. Crucially, multiple Weyl-like nodes emerge in the electronic band structure due to strong spin-orbit coupling, whose positions relative to the Fermi level is sensitively modulated by the canting angles of the self-intercalated Cr cations. These nodes contribute strongly to the Berry curvature and AHE conductivity.This component competes with the contribution from bands that are less affected by the self-intercalation, resulting in a sign change in AHE with temperature and the emergence of additional humps and dips. The findings provide compelling evidence for the intrinsic origin of the unconventional AHE in Cr2Te3and further establish self-intercalation as a control knob for engineering AHE in complex magnets.

Giant Domain Wall Anomalous Hall Effect in a Layered Antiferromagnet EuAl_{2}Si_{2}.

Generally, the dissipationless Hall effect in solids requires time-reversal symmetry breaking (TRSB), where TRSB induced by external magnetic field results in the ordinary Hall effect, while TRSB caused by spontaneous magnetization gives rise to the anomalous Hall effect (AHE) which scales with the net magnetization. The AHE is therefore not expected in antiferromagnets with vanishing small magnetization. However, large AHE was recently observed in certain antiferromagnets with noncollinear spin structure and nonvanishing Berry curvature. Here, we report another origin of AHE in a layered antiferromagnet EuAl_{2}Si_{2}, namely, the domain wall (DW) skew scattering with Weyl points near the Fermi level, in experiments for the first time. Interestingly, the DWs form a unique periodic stripe structure with controllable periodicity by external magnetic field, which decreases nearly monotonically from 975nm at 0T to 232nm at 4T. Electrons incident on DW with topological bound states experience strong asymmetric scattering, leading to a giant AHE, with the DW Hall conductivity (DWHC) at 2K and 1.2T reaching a record value of ∼1.51×10^{4} Scm^{-1} among bulk systems and being 2 orders of magnitude larger than the intrinsic anomalous Hall conductivity. The observation not only sets a new paradigm for exploration of large anomalous Hall effect, but also provides potential applications in spintronic devices.

Two-Dimensional Rare-Earth-Based Half-Metals with Topological Bimerons.

Two-dimensional magnets with spontaneous topological spin textures have important application prospects in highly integrated spintronic devices. However, so far, the predicted two-dimensional magnets with topological spin textures are mainly based on transition metals, and most of them are semiconductors or metals. Here, based on first-principles calculations, we predict two-dimensional rare-earth-based half-metallic monolayer GdA2N4 (A = Ge, Sn), with 100% spin polarization. Spontaneous topological spin textures, i.e., bimeron clusters, are revealed in those monolayers due to the magnetic frustration and easy-plane magnetic anisotropy. The bimeron clusters can be efficiently tuned through biaxial strain and driven by in-plane spin-polarized current. These results underscore the promising potential of rare-earth-based two-dimensional half-metals for spintronic device applications.

In-plane strain tuning multiferroicity in monolayer van der Waals NiI2

Multiferroic order with the engineered levels of strain in monolayer NiI2 is explored based on density functional theory calculations and Monte Carlo simulations. Through the investigation of strain-free monolayer NiI2, we find that the first nearest neighbor and third nearest neighbor exchange interactions play an essential role in the formation of its magnetic phase diagrams. The competition of these interactions induces magnetic frustration, leading to the formation of proper-screw helimagnetic ground state. We further show that these conclusions drawing from the strain-free monolayer can be well generalized to the cases within our engineered range of strains. Notably, our calculations show that with 6% tensile strain on the a-axis and 8% compressive strain on the b-axis, the Néel temperature TN can be significantly enhanced to 101 K, about 5 times larger than that of the strain-free one. The strength of spontaneous electric polarizations can also be more than doubled under 8% uniform compressive strain on both axis. Our work suggests that strain is a promising way to tune multiferroic orders in the monolayer NiI2, with the potential to significantly promote its transition temperatures and electric polarizations, therefore broaden the prospect of its applications in spintronics devices.

Tunability of half metallicity and thermoelectric indicators in Na2TaX6 (X = Cl, Br) vacancy ordered double perovskites

With the growing development in spintronics and thermoelectrics, researchers across the globe are extensively trying to fabricate and characterize novel materials. In this regard, the current work analyses the magnetic and thermoelectric characteristics of vacancy-ordered double perovskites Na2TaX6 (X = Cl, Br) computed using density functional theory. The geometry optimization reveals a cubic crystal structure with a relatively more stable ferromagnetic state. The mechanical and thermodynamic stability analyses also indicate the stability of both compounds. The computed electronic band structures demonstrate a half-metallic (HM) nature with metallic behavior in the up-spin channel. A semiconducting nature in down-spin configuration shows a direct bandgap of 3.6 eV and 4 eV for Na2TaCl6 and Na2TaBr6, respectively. The computation of transport parameters is found suitable for thermoelectric device applications. The present study demonstrates the high potential of the examined materials for applications in energy conversion and spintronics devices.

Room-temperature ferromagnetic MnGa nanoparticles in dilute magnetic semiconductor (Ga, Mn)As thin film: preparation and characterization

The GaAs based diluted magnetic semiconductor, (Ga, Mn)As, with the unique advantage of manipulating the spin and charge was widely investigated in the scientific community and considered as a potential material for the spintronic devices. However, its Curie temperature (Tc), which is limited to around 200 K, hinders the research progress of diluted magnetic semiconductors for potential device applications. Herein, we propose an approach to prepare the MnGa nanoparticles embedded in (Ga, Mn)As matrix using the magnetron sputtering deposition of Mn on GaAs surface, followed by the nano-second pulsed laser annealing (PLA), which gives aTcabove 400 K. We demonstrate that the MnGa nanoparticles are only formed in (Ga, Mn) As thin film during the nano-second PLA under a critical range of energy density (0.4-0.5 J cm-2). The highest achieved coercivity, saturation magnetization and remanent magnetization are 760 Oe, 11.3 emu cm-3and 9.6 emu cm-3, respectively. This method for preparing the hybrid system of ferromagnetic metal/dilute magnetic semiconductor builds a platform for exploring the interesting spin transport phenomenon and is promising for the application of spintronic devices.

Novel B6P6X (X=As, Sb) monolayers for antiferromagnetic spintronics and hydrogen storage

Embedding foreign atoms into porous two-dimensional (2D) materials has emerged as a promising strategy to tailor their electronic, magnetic, and adsorption properties, enabling promising applications in energy storage and spintronics devices. In this work, spin-polarized density functional theory (DFT) calculations were employed to investigate the ground state properties and hydrogen (H2) storage of interstitially X = As and Sb atom doped B6P6 (B6P6X) graphenylene monolayers. The resulting B6P6X (X = As, Sb) monolayers exhibit very good mechanical, dynamical, and thermal stabilities with antiferromagnetic (AFM) ground states. Electronic structure calculations reveal AFM semiconducting behavior for both monolayers, with indirect/direct band gaps of 0.71/0.60 eV (PBE) and 2.19/2.14 eV (HSE06) for B6P6As/B6P6Sb, respectively. All B6P6X monolayers exhibit an in-plane easy magnetization axis. The obtained Berezinskii–Kosterlitz–Thouless transition (BKT) temperature value of B6P6Sb monolayer is 268.74 K. Furthermore, the H2 storage capabilities of these B6P6X monolayers were examined. We find that B6P6As and B6P6Sb monolayers can each adsorb up to 48H2 molecules with an average adsorption energy (Ea) of -0.14 eV/H2. The corresponding H2 storage gravimetric capacities are 6.91 wt% for B6P6As@48H2 and 6.10 wt% for B6P6As@48H2, surpassing the U.S. Department of Energy’s 2025 target of 5.50 wt%. These findings highlighting the potential of B6P6X (X = As, Sb) monolayers for AFM spintronics and H2 storage applications.

Electronic Structure, Elasticity, Magnetism of Mn2XIn (X = Fe, Co) Full Heusler Compounds under biaxial strain: First-Principles Calculations

Abstract The electronic structure, elasticity, and magnetic properties of the Mn2XIn (X = Fe, Co) full-Heusler compounds are comprehensively investigated via first-principles calculations. The calculated elastic constants indicate that both Mn2FeIn and Mn2CoIn possess ductility. At the optimal lattice constants, the magnetic moments are found to be 1.40 μB/f.u for Mn2FeIn and 1.69 μB/f.u for Mn2CoIn. Under the biaxial strain ranging from -2% to 5%, Mn2FeIn demonstrates a remarkable variation in the spin polarization, spanning from -2% to 74%, positioning it as a promising candidate for applications in spintronic devices. Analysis of the electronic structure reveals that the change in spin polarization under strain is due to the shift of the spin-down states at the Fermi surface. Additionally, under biaxial strain, the magnetic anisotropy of Mn2FeIn undergoes a transition of easy-axis direction. Utilizing second-order perturbation theory and electronic structure analysis, the variation in magnetic anisotropy with strain can be attributed to changes of d-orbital states near the Fermi surface.

Magnetic proximity effect and spin transport properties of MnPc/CuPc/MnPc molecular spintronic device

Molecular-scale spintronic devices show great application potential in information storage due to tiny size and rich controllability. Spin transport of molecular devices relies heavily on the magnetic interaction between magnetic metal atom and molecule, which is the core of determining the performance of spintronic devices. In this study, the magnetic proximity effect in MnPc/CuPc/MnPc molecular device and the influence on spin transport were investigated using non-equilibrium Green’s function method in combination with density functional theory. Mn atoms in MnPc molecules not only endow magnetism with system, but also trigger magnetic proximity effect which works in synergy with the spin filtering of phthalocyanine molecules to achieve a spin injection efficiency of 100 % in molecular device, and this efficiency remains stable under bias voltage. The MnPc/CuPc/MnPc molecular device shows a tunneling magnetoresistance ratio of up to 4165 % at 5 mV, indicating potential application in multifunctional spintronic devices. This work elucidates the unique physical properties and excellent performance of MnPc/CuPc/MnPc molecular device, providing valuable insights for spintronic applications.

Investigations on full-Heusler alloys Mn2TaAl and Mn2WAl for spintronic and thermoelectric applications

Investigations on full-Heusler alloys Mn2TaAl and Mn2WAl for spintronic and thermoelectric applications

Unveiling half-metallic, thermoelectric and optoelectronic behavior of the new Heusler alloy RbCrZ (Z = Si, Ge): a DFT perspective

Abstract Utilizing the density functional theory (DFT) method, this study aims to predict with precision the structural, elastic, electronic, magnetic, thermoelectric, thermal, and optical properties of two recently discovered half-Heusler alloys, namely RbCrSi and RbCrGe. The exchange and correlation potential are accounted for using the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE) and the Tran–Blaha-modified Becke–Johnson exchange potential (TB-mBJ). Through structural analysis, it is observed that both RbCrSi and RbCrGe alloys exhibit energetic stability in a type-3 structure with a ferromagnetic (FM) state. Both alloys exhibit half-metallic properties and integer magnetic moments of 3 μB, following the Slater-Pauli rule. Additionally, elastic calculations confirm their mechanical stability and anisotropic ductile behavior. The quasi-harmonic Debye model (QHDM) is employed for calculating thermodynamic properties, while the BoltzTraP code, based on semi-classical Boltzmann theory (SCBT), is utilized for evaluating thermoelectric properties. Findings reveal that RbCrZ alloys (with Z = Si, Ge) exhibit high figure of merit (ZT) values nearing unity at highest temperature. Consequently, the newfound half-Heusler alloys RbCrSi and RbCrGe hold significant promise for applications in thermoelectricity and spintronic devices. This comprehensive analysis underscores the potential of these alloys in the realm of renewable energy applications.

Switchable Photovoltaic Effect and Robust Nonlinear Optical Response in a High-Temperature Molecular Ferroelectric [C8N2H22][PbI4

Hybrid organic-inorganic molecular ferroelectrics (HOIMFs) have garnered significant attention for their potential applications in nonvolatile memory and spintronic devices. However, few efforts have been devoted to the photoelectric properties of lead halide molecular ferroelectrics, despite the fact that robust ferroelectricity and flexibility are desirable for thin-film photoelectric devices. Herein, we present a novel lead halide molecular ferroelectric [C8N2H22][PbI4] (1) synthesized hydrothermally. A polar monoclinic structure of 1 was solved by single-crystal X-ray diffraction and second-harmonic generation (SHG) tests. A direct band gap of 2.36 eV was confirmed by UV-vis spectrum and theoretical calculation. Hysteresis measurements demonstrated inherent room-temperature (RT) ferroelectricity in 1 with a spontaneous polarization (Ps) of 3.2 μC/cm2. The 1-based photoelectric device shows a notable photovoltaic (PV) effect with Voc ∼ 0.27 V, Jsc ∼ 38 nA/cm2 under AM 1.5 G illumination, and a rapid response time of ∼1.5 ms. A considerable enhancement in PV performance has been achieved by adjusting the ferroelectric polarization, resulting in a maximum Voc ∼ 0.75 V, Jsc ∼ 2.28 μA/cm2. Notably, 1 exhibits a rather large SHG signal, which is approximately 2.61-fold higher than that of KH2PO4 (KDP) upon a 1064 nm laser radiation. This study offers a bright avenue for lead halide molecular ferroelectrics as promising optoelectronic devices and SHG materials.

Circular photocurrents in centrosymmetric semiconductors with hidden spin polarization

Centrosymmetric materials with site inversion asymmetries possess hidden spin polarization, which remains challenging to be converted into spin currents because the global inversion symmetry is still conserved. This study demonstrates the spin-polarized circular photocurrents in centrosymmetric transition metal dichalcogenide semiconductors at normal incidence without applying electric bias. The global inversion symmetry is broken by using a spatially-varying circularly polarized light beam, which could generate spin gradient owing to the hidden spin polarization. The dependence of the circular photocurrents on electrode configuration, illumination position, and beam spot size indicates an emergence of circulating electric current under spatially inhomogeneous light, which is associated with the deflection of spin-polarized current through the inverse spin Hall effect. The circular photocurrents is subsequently utilized to probe the spin polarization and the inverse spin Hall effect under different excitation wavelengths and temperatures. The results of this study demonstrate the feasibility of using centrosymmetric materials with hidden spin polarization and non-vanishing Berry curvature for spintronic device applications.

Magnetoelectric Tuning of 2D Ferromagnetism in 1T-CrTe2 through In2Se3 Substrate.

Electric field control of two-dimensional (2D) materials with optimized magnetic properties is not only of scientific interest but also of technological importance in terms of the functionality of various nanoscale devices. Here, we report the multiferroic control of the 2D ferromagnetism in 1T-CrTe2 monolayer through a ferroelectric In2Se3 sublayer. Our results reveal the effect of polarization switching on the electronic structures and magnetic properties of 1T-CrTe2/In2Se3 heterostructures, enabling effective manipulation of their magnetic anisotropy energy (MAE) and magnetization orientation. Additionally, we also demonstrate the strong dependence of their MAE and switching effect on the external strain and surface hydrogenation. Notably, polarization switching exhibits a reversal modification in the hydrogenated multiferroic structures. These tunable behaviors are primarily attributed to the alteration of p-orbitals near the Fermi level of the interfacial Te atoms due to magnetoelectric coupling. Our findings suggest the potential of 1T-CrTe2/In2Se3 heterojunctions for the practical application of 2D multiferroic spintronic devices.

Observation of Néel-type magnetic skyrmion in a layered non-centrosymmetric itinerant ferromagnet CrTe1.38

Magnetic skyrmions are nanoscale vortex-like magnetization textures that hold great promise for next-generation memory and spintronic devices. While extensive research has focused on discovering such localized spin textures in bulk magnets and multilayers with heavy metals, there is a growing interest in finding them in two-dimensional (2D) magnetic materials. In this research work, we report two distinct phases of the 2D CrxTey family: non-centrosymmetric CrTe1.38 and centrosymmetric CrTe0.96, with a Curie temperature of around 200 and 300 K, respectively. Detailed magnetic study indicates a prominent out-of-plane magnetic anisotropy in CrTe1.38. In contrast, CrTe0.96 exhibits a weak uniaxial magnetic anisotropy. Lorentz transmission electron microscopy shows that the spontaneous ferromagnetic ground state of CrTe1.38 consists of Néel skyrmions, whereas CrTe0.96 exhibits Bloch domain walls, consistent with their crystalline symmetries. This research expands the quasi-2D CrxTey family and opens up new avenues for exploring non-trivial spin structures and their potential applications in spintronic devices.

Polar phonons features and intrinsic dielectric properties of RE2CoMnO6 (RE = Tb, Dy, Ho, Tm and Yb) double perovskites

RE-based double perovskite (DP) oxides of the RE₂TMTM'O₆ family exhibit intriguing magnetodielectric (MD) properties and magnetocaloric effects (MCEs), making them promising candidates for applications in high-performance supercapacitors, memories, spintronic devices, and cryogenic magnetic refrigeration. This paper addresses the vibrational properties of RE2CoMnO6 (RE = Tb, Dy, Ho, Tm, and Yb) ceramics for the first time using infrared reflectance spectroscopy. The dielectric merit factors in the microwave (MW) range, including the quality factor (Qu) and the static dielectric constant (ɛ0), were estimated. It was observed that the intrinsic dielectric constants decrease from approximately 26.2 to 14.4 as the rare earth ionic radius decreases. The mean values of these compounds suggest their suitability for applications in MW circuitry devices.