Spintronic Applications Research Articles

First-principles study of robust half-metallic ferromagnetism and electronic structure of the Heusler compounds Co2-xCrxMnGe

Abstract Half-metallic ferromagnets (HMFs) are among the most promising materials in the field of spintronics because of their distinct band structures, which consist of two characteristic subbands, one with semiconductor-like behaviour and the other with metallic features. Using density functional theory-based calculations, we have carried out in-depth studies to predict the effects of Co replacement by Cr on electronic structure as well as the magnetic properties of Co2-xCrxMnGe with 0 ≤ x ≤ 1. The results demonstrate that the alloys are stable in the ferromagnetic phase with half-metallic nature. The origin of ferromagnetism can be explained by Ruderman-Kittel-Kasuya-Yosida (RKKY), like exchange interaction. Due to their high Curie temperatures, which increase linearly with the total magnetic moment, all alloys are suitable for applications at and above room temperature. Besides, the electronic properties have revealed a transition from half-metallic to semi-metallic character for higher doping concentration (x = 0.75, x = 1.0). The calculated total magnetic moments, however, decrease with increasing doping concentration, consistent with the Slater-Pauling rule. The observed high value of spin polarisation of all the studied compounds suggests their futuristic roadmaps for possible spintronics applications beyond room temperature.

Exploring Spin-Crossover Cobalt(II) Single-Ion Magnets as Multifunctional and Multiresponsive Magnetic Devices: Advancements and Prospects in Molecular Spintronics and Quantum Computing Technologies

Spin-crossover (SCO) and single-ion magnets (SIMs), or their mixed SCO-SIM derivatives, are a convenient solution in the evolution from molecular magnetism toward molecular spintronics and quantum computing. Herein, we report on the current trends and future directions on the use of mononuclear six-coordinate CoII SCO-SIM complexes with potential opto-, electro-, or chemo-active 2,6-pyridinediimine (PDI)- and 2,2′:6′,2′-terpyridine (TERPY)-type ligands as archetypical examples of multifunctional and multiresponsive magnetic devices for applications in molecular spintronics and quantum computing technologies. This unique class of spin-crossover cobalt(II) molecular nanomagnets is particularly well suited for addressing and scaling on different supports, like metal molecular junctions or carbon nanomaterials (CNMs) and metal–organic frameworks (MOFs) or metal-covalent organic frameworks (MCOFs), in order to measure the single-molecule electron transport and quantum coherence properties, which are two major challenges in single-molecule spintronics (SMS) and quantum information processing (QIP).

Room-temperature in-plane ferromagnetism in Co-substituted Fe5GeTe2 investigated by magnetic X-ray spectroscopy and microscopy

Abstract The exploration of two-dimensional (2D) van der Waals ferromagnets has revealed intriguing magnetic properties with significant potential for spintronics applications. In this study, we examine the magnetic properties of Co-doped Fe5GeTe2 using X-ray photoemission electron microscopy (XPEEM) and X-ray magnetic circular dichroism (XMCD), complemented by density functional theory (DFT) calculations. Our XPEEM measurements reveal that the Curie temperature (T C) of a bilayer of (CoxFe1-x)5-δGeTe2 (with x = 0.28) reaches ∼300 K — a notable enhancement over most 2D ferromagnets in the ultrathin limit. Interestingly, the TC shows only a small dependence on film thickness (bulk T C ≈ 340 K), in line with the observed in-plane magnetic anisotropy and robust in-plane exchange coupling. XMCD measurements indicate that the spin moments for both Fe and Co are significantly reduced compared to the theoretical values. These insights highlight the potential of Co-doped Fe5GeTe2 for stable, high-temperature ferromagnetic applications in 2D materials.

Bimeron stability and non-reciprocal energy behavior in magnetic nanodots

Magnetic bimerons, solitonic spin textures with the same topology as skyrmions, have attracted attention for their potential in spintronic applications. In this work, we explore the stabilization conditions and energy characteristics of bimerons in a circular nanodot through micromagnetic simulations and analytical calculations. We examine the dependence of the size, position, and orientation of the meron and antimeron cores on the anisotropy-induced easy-axis. Our results demonstrate that the bimeron orientation relative to the surrounding homogeneous state is strongly influenced by the Dzyaloshinskii–Moriya interaction type. Additionally, we show a non-reciprocal energy dependence on the bimeron's position within the nanodot. We also obtain that the bimeron size decreases with increasing anisotropy, while its equilibrium position is displaced from the nanodot center. Furthermore, an analysis of energy barriers reveals that bimeron contraction is the dominant annihilation mechanism under thermal fluctuations. These insights are valuable for developing magnetic devices that require precise control of topological spin textures.

Co–Fe–Al Heusler Alloy Nanowires Prepared by Electrospinning Route for Spintronics Applications

Co–Fe–Al Heusler Alloy Nanowires Prepared by Electrospinning Route for Spintronics Applications

Magnetic Properties of All-d Metallic Heusler Compounds: A First-Principles Study

All-d metallic Heusler compounds are promising materials for nanoelectronic applications. Such materials combining 3d, 4d, and 5d atoms have not yet been studied. In this respect, we perform ab initio electronic structure calculations and focus on Co2MnZ, Rh2MnZ, and Ru2MnZ compounds, where Z represents transition metal atoms from groups 3B, 4B, 5B, and 6B of the periodic table. Our results demonstrate that most of these compounds exhibit a distinctive region of very low minority-spin state density at the Fermi level when crystallized in the L21 lattice structure. The Co-based compounds follow a Slater–Pauling behavior for their total spin magnetic moments, while the Ru-based compounds consistently deviate from the predicted Slater–Pauling values. Rh-based compounds show similarities to Co-based compounds for lighter Z atoms and to Ru-based compounds for heavier Z atoms. We find that the choice of the Z element within the same periodic table column has only a minor effect on the results, except for the Rh2Mn(Cr, Mo, W) compounds. Our findings suggest that these compounds hold significant promise for applications in spintronics and magnetoelectronics.

Pure spin currents induced by asymmetric H-passivation in B3C2P3 nanoribbons.

Inspired by the recently reported novel two-dimensional material B3C2P3, we performed one-dimensional shearing along the zigzag direction to obtain four B3C2P3 nanoribbons with various edge atom combinations. An asymmetric hydrogen passivation scheme was employed to modulate the electronic properties and successfully open the band gap, especially the 2H-1H passivation with dihydrogenation and monohydrogenation at the top and bottom edges, respectively, achieving bipolar magnetic semiconductors with edge P-atoms contributing to the main magnetism. Furthermore, three crucial spin-polarized transmission spectra yielded a significant spin-dependent Seebeck effect (SDSE), displaying superior thermoelectric conversion capabilities by generating pure spin currents. Our work shows that this asymmetric H-passivation effectively enables the enhancement of the spin caloritronic transport properties of the B3C2P3, which is of great significance for the exploitation of novel materials and their applications in spintronics.

Electronic, magnetic, and topological properties of ferromagnetic 2D perovskite-type oxides

Abstract Two-dimensional (2D) materials within the hematene-type binary oxides and perovskites family have recently gathered huge research interest for nanoelectronic devices. However, the exploration of their fascinating topological properties remains limited. Herein, through first-principles calculations, we systematically examine the electronic, magnetic, and topological properties of substitutionally doped 2D ABO3 (A=As, Sb, or Bi, and B = V, Nb, or Ta) perovskite structures at the B site of a B2O3 system. Interestingly, the atomic substitution makes the 2D ABO3 structures dynamically stable. Our detailed calculations show the ferromagnetic and antiferromagnetic phases of these materials. The calculated Chern number (C) for the ferromagnetic 2D ABO3 (A = As, Sb, or Bi, B = Nb or Ta) suggests their topologically non-trivial phases. Furthermore, the computed nontrivial Berry curvature highlights the topological properties in AsNbO3. These findings highlight opportunities in 2D-ABO3 materials, for applications in spintronics.

Origin of the contrasting magnetic stability of antiferromagnetic CuMnAs and CuMnSb

Antiferromagnetic (AFM) materials exhibit great potential for next-generation spintronic applications because they have some unique characteristics compared to ferromagnetic (FM) materials. For example, the successful electrical manipulation and detection of the Néel vector at room temperature was recently realized for AFM CuMnAs in its tetragonal phase. The Néel temperature (TN) for tetragonal CuMnAs is about 480 K. In contrast, cubic half-Heusler CuMnSb, despite it is isovalent to CuMnAs, exhibits a notably lower TN of about 50 K, limiting its applicability in spintronic devices. The physical origin behind the stark difference in TN between the two compounds remains unclear. In this study, we investigate both CuMnAs and CuMnSb in both tetragonal and cubic phases. We find that the band crossing between the valence band and conduction band is more pronounced in CuMnSb compared to CuMnAs. This disparity arises from the higher energy level of the Sb 5p orbital relative to the As 4p orbital, resulting in a greater abundance of carriers in CuMnSb than in CuMnAs. Utilizing the effective band coupling model, we establish a relationship between carrier concentration and magnetic stability and confirm that the elevated carrier concentration is the origin of the weakened antiferromagnetism observed in both phases of CuMnSb.

Monolayer Magnetic Metal with Scalable Conductivity.

2D magnets have emerged as a class of materials highly promising for studies of quantum phenomena and applications in ultra-compact spintronics. Current research aims at design of 2D magnets with particular functional properties. A formidable challenge is to produce metallic monolayers: the material landscape of layered magnetic systems is strongly dominated by insulators; rare metallic magnets, such as Fe3GeTe2, become insulating as they approach the monolayer limit. Here, electron transport measurements demonstrate that the recently discovered 2D magnet GdAlSi - graphene-like AlSi layers coupled to layers of Gd atoms - remains metallic down to a single monolayer. Band structure analysis indicates the material to be an electride, which may stabilize the metallic state. Remarkably, the sheet conductance of 2D GdAlSi is proportional to the number of monolayers - a manifestation of scalable conductivity. The GdAlSi layers are epitaxially integrated with silicon, facilitating applications in electronics.

Computational characterization of structural, electronic, elastic and magnetic properties of double half-Heusler alloy Fe2MnCoGe2

Using the augmented plane wave method based on density functional theory and implemented in the WIEN2k code, we study the structural, elastic, electronic, and magnetic properties of FeCoGe, FeMnGe, and the parent half-Heusler (HH) alloys, as well as their derivative Fe2CoMnGe2 double half-Heusler (DHH) compounds. By analysing the stability of the HH structure in both the ferromagnetic and non-magnetic phases of FeCoGe and FeMnGe alloys, we determine that the latter phase of type II and type III FeCoGe and FeMnGe arrangements is the most stable. The Fe2CoMnGe2 DHH alloy, which is derived from the magnetic and structural ground states of FeCoGe and FeMnGe HH alloys, is found to be most stable in the type II arrangement. Among these materials, the FeMnGe HH alloy demonstrates greater resistance to reversible deformation by shear strain, indicated by its higher Young's modulus, while FeCoGe shows the best overall resistance to deformation. The electronic structures of FeCoGe, FeMnGe, and Fe2CoMnGe2 compounds reveal metallic behavior in the spin-up channel and semiconducting behavior in the spin-down channel. Their half-metallic gaps are 0.437 (0.181) eV, 0.543 (0.224) eV, and 0.353 (0.035) eV, respectively, with Fe2CoMnGe2 DHH retaining half-metallicity despite a lower band gap. The total magnetic moments for FeCoGe, FeMnGe, and Fe2CoMnGe2 are found to be 3, 1, and 4 μB, respectively. Given their half-metallic properties, these alloys show potential as candidates for spintronic applications.

Unexpected Magnetic Moments in Manganese-Doped (CdSe)13 Nanoclusters: Role of Ligands.

This study explores the enhancement in magnetic and photoluminescence properties of Mn2+-doped (CdSe)13 nanoclusters, significantly influenced by the introduction of paramagnetic centers through doping, facilitated by optimized precursor chemistry and precisely controlled surface ligand interactions. Using a cost-effective and scalable synthesis approach with elemental Se and NaBH4 (Se-NaBH4) in n-octylamine, we tailored bonding configurations (Cd-O, Cd-N, and Cd-Se) on the surface of nanoclusters, as confirmed by EXAFS analysis. These bonding configurations allowed for tunable Mn2+-doping with tetrahedral coordination, further stabilized by hydrogen-bonded acetate ligands, as evidenced by 13C NMR and IR spectroscopy. Mulliken charge analysis indicates that the charge redistribution on Se2- suggests electron transfer between surface ligands and the nanocluster, contributing to spin fluctuations. These tailored configurations markedly increased the nanoclusters' magnetic susceptibility and photoluminescence efficiency. The resulting nanoclusters demonstrated a clear concentration-dependent response in emission lifetimes and intensities upon exposure to magnetic field effects (MFE) and spin-spin coupling, alongside a large magnetic moment exceeding 40 μB at 180K. These findings highlight the potential of these nanoclusters for magneto-optical devices and spintronic applications, showcasing their tunable magnetic properties and exciton dynamics.

Unexpected Magnetic Moments in Manganese‐Doped (CdSe)13 Nanoclusters: Role of Ligands

This study explores the enhancement in magnetic and photoluminescence properties of Mn2+‐doped (CdSe)13 nanoclusters, significantly influenced by the introduction of paramagnetic centers through doping, facilitated by optimized precursor chemistry and precisely controlled surface ligand interactions. Using a cost‐effective and scalable synthesis approach with elemental Se and NaBH4 (Se‐NaBH4) in n‐octylamine, we tailored bonding configurations (Cd‐O, Cd‐N, and Cd‐Se) on the surface of nanoclusters, as confirmed by EXAFS analysis. These bonding configurations allowed for tunable Mn2+‐doping with tetrahedral coordination, further stabilized by hydrogen‐bonded acetate ligands, as evidenced by 13C NMR and IR spectroscopy. Mulliken charge analysis indicates that the charge redistribution on Se2‐ suggests electron transfer between surface ligands and the nanocluster, contributing to spin fluctuations. These tailored configurations markedly increased the nanoclusters' magnetic susceptibility and photoluminescence efficiency. The resulting nanoclusters demonstrated a clear concentration‐dependent response in emission lifetimes and intensities upon exposure to magnetic field effects (MFE) and spin‐spin coupling, alongside a large magnetic moment exceeding 40 μB at 180K. These findings highlight the potential of these nanoclusters for magneto‐optical devices and spintronic applications, showcasing their tunable magnetic properties and exciton dynamics.

Unveiling the impact of Ni doping on the structural, electronic, and magnetic properties of nanocrystalline FeCo2O4spinel oxide: A combined experimental andab initioinvestigations.

In the present work, nanocrystalline samples of compositions 〖Ni〗_x 〖Fe〗_(1-x) 〖Co〗_2 O_4 (x = 0.0, 0.25, 0.50, and 0.75) have been synthesized via co-precipitation method by annealing at 900 oC. The nanocrystalline samples of compositions Ni0.25Fe0.75Co2O4 (D0.25) and Ni0.5Fe0.5Co2O4 (D0.5) crystallize in a pure spinel phase, whereas Ni0.75Fe0.25Co2O4 (D0.75) show the existence of secondary phase of NiO, as confirmed by the X-ray diffraction analysis. The particle size and lattice strain in the samples both decrease as Ni substitution is increased. The field-dependent dc magnetization M(H) virgin curve measured at 5 K for sample D0.75 shows the existence of field-induced metamagnetic transition, while this behavior is absent in samples D0.5 and D0.25. Dynamic magnetic properties have been investigated by ac susceptibility measurement, which shows a strong frequency dependence behavior resulting from the blocking/spin-glass freezing states depending upon the amount of Ni substitution and the range of measurement temperature. High-resolution X-ray photoelectron spectroscopy (HR-XPS) analysis reveals the presence of mixed valence states of Fe2+/Fe3+, Co2+/Co+3, and Ni2+/Ni+3 in all samples. Using first principles-based Density Functional Theory (DFT) calculations with HSE06 exchange-correlation functional predicts the correct description of ground state which is ferrimagnetic and insulating in their inverse spinel case for D0.25, D0.5, and D0.75 samples that agreed well with our experimental observations. A closer look at the electronic structure near the Fermi level (EF) of Ni-doped samples suggests a typical Mott-Hubbard insulating state while it is found to be a mixture of charge-transfer and Mott-Hubbard insulating state for parent compound FeCo2O4. The obtained spin-dependent gap hierarchy can have possible application in spintronics. We have studied a detailed correlation between experiment and theory.

Magneto‐Capacitance of PEDOT:PSS Thin Films; Effects of a Two‐Phase System and Coulomb Interaction

AbstractThe study of the net magneto‐capacitance, C(B), in thin films of the conducting polymer Poly(3 4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is presented. In the films there are charged electrically‐conducting PEDOT‐rich regions surrounded by PSS insulating charged material. The high‐conductivity grade PEDOT:PSS thin films are studied at low temperature, where the hopping conduction is dominant. It is experimentally observed that there is a finite net magneto‐capacitance, C(B), in the temperature range T = 1.7–3 K. Thus, the observed C(B) is a direct evidence for an intra‐site Coulomb interaction, U ≈ 2 meV, among the mobile charge carriers in the PEDOT‐rich regions. The lifting of spin degeneracy motivates PEDOT for use in spintronic applications.

Strong Magneto‐chiroptical Effects through Introducing Chiral Transition‐metal Complex Cations to Lead Halide

The interplay between chirality with magnetism can break both the space and time inversion symmetry and have wide applications in information storage, photodetectors, multiferroics and spintronics. Herein, we report the chiral transition‐metal complex cation‐based lead halide, R‐CDPB and S‐CDPB. In contrast with the traditional chiral metal halides with organic cations, a novel strategy for chirality transfer from the transition‐metal complex cation to the lead halide framework is developed. The chiral complex cations directly participate the band structure and introduce the d‐d transitions and tunable magneto‐chiroptical effects in both the ultraviolet and full visible range into R‐CDPB and S‐CDPB. Most importantly, the coupling between magnetic moment of the complex cation and chiroptical properties is confirmed by the magneto‐chiral dichroism. For the band‐edge transition, the unprecedented modulation of +514% for S‐CDPB and ‐474% for R‐CDPB was achieved at ‐1.3 Tesla. Our findings demonstrate a novel strategy to combine chirality with magnetic moment, and provide a versatile material platform towards magneto‐chiroptical and chiro‐spintronic applications.

Bent zigzag graphene nanoribbons for spintronic applications

Abstract We investigate a spintronic device utilizing bent zigzag graphene nanoribbons (ZGNRs) to explore their spin-dependent electronic and transport properties. Employing a mean-field Hubbard model and the Landauer-Büttiker formalism, we examine the effects of curvature on a large-scale bent ZGNR, revealing a spin-semiconducting phase in the antiferromagnetic ground state. The device comprises a circularly curved nanoribbon connected to two straight ZGNRs, forming a two-terminal, stretchable system. Our findings demonstrate that the spin energy gap and spin-splitting effects in bent ZGNRs are highly tunable via curvature parameters—total rotation, radius, and width. Even minimal curvature induces significant spin-dependent behavior and spin Seebeck coefficient (SSC), resulting in full spin polarization in both the density of states and the transmission coefficient. The degree of spin polarization increases with the bending parameter, leading to enhanced spin-polarized current and a substantial SSC. These results suggest that bent ZGNRs are promising for advancing spintronic applications, particularly in flexible device technologies.

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.

Biocompatibility of Bi2Se3 regarding primary mixed retinal cells

Abstract Bismuth chalcogenides have a groundbreaking impact on materials science because of their potential applications in spintronics and optoelectronics, especially for their properties as topological insulators. Investigation of the biocompatibility of the electrode material at the tissue/electrode interface is essential to assess the use of topological insulators in bioelectronics. Here, we addressed the biocompatibility of Bi2Se3 by demonstrating that porcine primary mixed retinal cells can survive on its surface with or without poly-D-lysine/laminin coating. Neuronal and glial cell survival were demonstrated using cell culture and imaging techniques. These results highlight the promising potential of Bi2Se3 for integration into bioelectronic devices, particularly for the development of neural interfaces and other biomedical applications.

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.