Search Results (180)

Spin transport behaviors in heavy metal/ferromagnetic insulator (HM/FI) bilayers have attracted considerable attention due to various novel phenomena and applications in spintronic devices. Herein, we investigate the planar Hall effect (PHE) in Pt/Tm₃Fe₅O₁₂ (Pt/TmIG) heterostructures at low temperatures; moment switching in the ferrimagnetic insulator TmIG is detected by using electrical measurements. Double switching hysteresis PHE curves are found in Pt/TmIG bilayers, closely related to the magnetic moment of Tm³⁺ ions, which makes a key contribution to the total magnetic moment of TmIG film at low temperature. More importantly, a magnetoresistance (MR) curve with double switching is found, which has not been reported in this simple HM/FI bilayer, and the sign of this MR effect is sensitive to the angle between the magnetic field and current directions. Our findings of these effects in this HM/rare earth iron garnet (HM/REIG) bilayer provide insights into tuning the spin transport properties of HM/REIG by changing the rare earth. Full article

Recently, a new class of magnetic material, termed altermagnets, has caught the attention of the magnetism and spintronics community. The magnetic phenomenon arising from these materials differs from traditional ferromagnetism and antiferromagnetism. It generally lacks net magnetization and is characterized by unusual non-relativistic spin-splitting and broken time-reversal symmetry. This leads to novel transport properties, such as the anomalous Hall effect, the crystal Nernst effect, and spin-dependent phenomena. Spin-dependent phenomena such as spin currents, spin-splitter torques, and high-frequency dynamics emerge as key characteristics in altermagnets. This paper reviews the main aspects pertaining to altermagnets by providing an overview of theoretical investigations and experimental realizations. We discuss the most recent developments in altermagnetism and prospects for exploiting its unique properties in next-generation devices. Full article

An altermagnet, characterized by its distinctive magnetic properties, may hold potential applications in diverse fields such as magnetic materials, spintronics, data storage, and quantum computing. As a prototypical altermagnet, RuO₂ exhibits spin polarization and demonstrates the advantageous characteristics of high electrical conductivity and low thermal conductivity. These exceptional properties endow it with considerable promise in the emerging field of thermal spintronics. We studied the electronic structure and thermoelectric properties of RuO₂; the constructed RuO₂/TiO₂/RuO₂ all-antiferromagnetic tunnel junction (AFMTJ) exhibited thermally induced magnetoresistance (TIMR), reaching a maximum TIMR of 1756% at a temperature gradient of 5 K. Compared with prior studies on RuO₂-based antiferromagnetic tunnel junctions, the novelty of this work lies in the thermally induced magnetoresistance based on its superior thermoelectric properties. In parallel structures, the spin-down current dominates the transmission spectrum, whereas in antiparallel structures, the spin-up current governs the transmission spectrum, underscoring the spin-polarized thermal transport. In addition, thermoelectric efficiency emphasizes the potential of RuO₂ to link antiferromagnetic robustness with ferromagnetic spin functionality. These findings promote the development of efficient spintronic devices and spin-based storage technology for waste heat recovery and emphasize the role of spin splitting in zero-magnetization systems. Full article

The spin polarization of current in a conventional ferromagnetic and semiconductor-based Rashba spin–orbit interaction (RSOI) in an infinite two-dimensional system and the electrical properties of the junction are described using the square lattice model. In particular, a suitable approach is devised to compute the particle transport characteristics in the junction, taking into consideration the interface quality. It is found that the spin polarization becomes strongly reliant on the spin-flip scattering potential at applied voltages close to the crossings of the semiconductor-based RSOI band. On the other hand, in the voltage near the middle band, the spin polarization of current is found to remain modest and not influenced by either the spin-flip or non-spin-flip scattering potentials. Full article

Diluted magnetic semiconductors (DMSs) represent a significant area of interest for research and applications in spintronics. Recently, DMSs derived from BaZn₂As₂ have garnered significant interest due to the record Curie temperature (T_C) of 260 K. However, the influence of doping on their magnetic evolution and transport characteristics has not been thoroughly investigated. This study aims to fill this gap through susceptibility and magnetization measurements, electric transport analysis, and muon spin relaxation and rotation (µSR) measurements on (Ba_1−xRb_x)(Zn_1−yMn_y)₂As₂ (0.1 ≤ x, y ≤ 0.25, BRZMA). Key findings include the following: (1) BRZMA showed a maximum T_C of 138 K, much lower than (Ba,K)(Zn,Mn)₂As, because of a reduced carrier concentration. (2) A substantial electromagnetic coupling is evidenced by a negative magnetoresistance of up to 34% observed in optimally doped BRZMA. (3) A 100% static magnetic ordered volume fraction is achieved in the low-temperature region, indicating a homogeneous magnet. (4) Furthermore, a systematic and innovative methodology has been initially proposed, characterized by clear step-by-step instructions aimed at enhancing T_C, grounded in robust experimental findings. The findings presented provide valuable insights into the spin–charge interplay concerning magnetic and electronic transport properties. Furthermore, they offer clear direction for the investigation of higher T_C DMSs. Full article

Tin oxide (SnO₂) is an attractive candidate for the electron transport layer (ETL) in perovskite-based solar cells because of its low temperature process requirement. The ability to form ETL layers at low temperatures opens up opportunities for the use of flexible and low-cost materials suitable for photovoltaic applications. The ETL is necessary for the extraction of electrons and charge separation from the perovskite active layer. Herein, we present a study of the effect of annealing temperature on SnO₂ used as an ETL. The annealing temperature of the SnO₂ has a considerable effect on the morphology, crystallinity, grain size, and surface topography of the SnO₂ layer. The surface properties of the ETL influence the structural properties of the perovskite films. In this study, the annealing temperature of the SnO₂, deposited using spin coating, was changed from 90 °C to 150 °C. The SnO₂ films annealed at 120$°$C resulted in reduced surface defects, improved electron extraction, and produced a significant increase in the grain size of the perovskite active layers. The increase in grain size led to improved efficiency of the PSCs. Devices annealed at 120 °C yielded PSCs with an average efficiency of 15% for a 0.36 cm² active area, while devices treated at 90 °C and 150 °C produced an average efficiency of 12%. The PSCs fabricated at low temperatures provide an effective technique for low-cost manufacturing, especially on flexible and polymer-based substrates. Full article

Metalloporphyrins and porphyrins (MPs) have garnered increasing attention as potential candidates for molecular-based electronic devices and single-atom catalysis. Recent studies have found that electronic structure calculations are important factors in controlling the performance of MPs as building blocks for single-molecule devices. Our study investigates metalloporphyrins with central 3d-metals from Sc to Cu and chalcogen containing anchoring groups such as -SH, -SeH, and -TeH substituted at the meso-position of the porphyrin rings. We carried out Density Function Theory (DFT)-based calculations to determine the ground state geometry, spin multiplicity, spatial distribution of the molecular orbitals, and electronic structure descriptors to gain insights into the reactivity trends and possible impact on factors influencing electron transport properties. The results suggest that the central metal shapes the spin multiplicity, while variations between sulfur, selenium, and tellurium play a role in charge distribution. This study provides insights into how the selection of the central metal and control of spin channels influence the electronic structure and reactivity of metalloporphyrin molecules. The knowledge provided here can play a role in the design of porphyrin-based molecular materials for diverse applications in molecular junctions, catalysis, photovoltaics, and sensing. Full article

The low-symmetry Weyl semimetallic Td-phase WTe₂ exhibits both a distinct out-of-plane damping torque (${\tau }_{\mathrm{DL}}$) and exceptional charge–spin interconversion efficiency enabled by strong spin-orbit coupling, positioning it as a prime candidate for spin–orbit torque (SOT) applications in two-dimensional transition metal dichalcogenides. Herein, we report on thickness-dependent unconventional out-of-plane ${\tau }_{\mathrm{DL}}$ in chemically vapor-deposited (CVD) polycrystalline Td-WTe₂ (t)/Ni₈₀Fe₂₀/MgO/Ti (Td-WTN-t) heterostructures. Angle-resolved spin-torque ferromagnetic resonance measurements on the Td-WTN-12 structure showed significant spin Hall conductivities of σ_SH,y = 4.93 × 10³ (ℏ/2e) Ω⁻¹m⁻¹ and σ_SH,z = 0.81 × 10³ (ℏ/2e) Ω⁻¹m⁻¹, highlighting its potential for wafer-scale spin–orbit torque device applications. Additionally, a detailed examination of magnetotransport properties in polycrystalline few-layer Td-WTe₂ films as a function of thickness revealed a marked amplification of the out-of-plane magnetoresistance, which can be ascribed to the anisotropic nature of charge carrier scattering mechanisms within the material. Spin pumping measurements in Td-WTN-t heterostructures further revealed thickness-dependent spin transport properties of Td-WTe₂, with damping analysis yielding an out-of-plane spin diffusion length of λ_SD ≈ 14 nm. Full article

By combining density functional theory with the non-equilibrium Green’s function method, we conducted a first-principles investigation of spin-dependent transport properties in a molecular device featuring a dynamic covalent chemical bridge connected to zigzag graphene nanoribbon electrodes. The effects of spin-filtering and spin-rectifying on the I–V characteristics are revealed and explained for the proposed molecular device. Interestingly, our results demonstrate that all three devices exhibit significant single-spin-filtering behavior in parallel (P) magnetization and dual-spin-filtering effects in antiparallel (AP) configurations, achieving nearly 100% spin-filtering efficiency. At the same time, from the I–V curves, we find that there is a weak negative differential resistance effect. Moreover, a high rectifying ratio is found for spin-up electron transport in AP magnetization, which is explained by the transmission spectrum and local density of state. The fundamental mechanisms governing these phenomena have been elucidated through a systematic analysis of spin-resolved transmission spectra and spin-polarized electron transport pathways. These results extend the design principles of spin-controlled molecular electronics beyond graphene-based systems, offering a universal strategy for manipulating spin-polarized currents through dynamic covalent interfaces. The nearly ideal spin-filtering efficiency and tunable rectification suggest potential applications in energy-efficient spintronic logic gates and non-volatile memory devices, while the methodology provides a framework for optimizing spin-dependent transport in hybrid organic–inorganic nanoarchitectures. Our findings suggest that such systems are promising candidates for future spintronic applications. Full article

Controllable intramolecular spin-polarized flow refers to the manipulation of spin-polarized electron transport within molecules through externally applied stimuli, thereby modulating their intramolecular spin characteristics and magnetic properties. In this work, we designed and synthesized four paramagnetic molecules, PDTN-NN, PDTN-IN, PO-NN, and PO-IN, by introducing nitronyl nitroxide (NN) and iminonitroxide (IN) radicals into phenothiazine and phenoxazine frameworks. Remarkably, we successfully generated the corresponding radical-substituted radical cations (diradical cations) and controlled their spin density distributions (SDDs) through redox stimuli. UV-Vis absorption spectroscopy, cyclic voltammetry (CV), electron paramagnetic resonance (EPR), and density functional theory (DFT) were employed to confirm the formation of diradical cations during the redox processes. Furthermore, EPR spectroscopy and DFT calculations were also employed to provide clear evidence of intramolecular magnetic coupling in the diradical cations. Full article

Among hole transport materials (HTMs), 2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) is the most frequently adopted, due to its suitable energy band level in conventional-type perovskite solar cells (PSCs). However, the high price of spiro-OMeTAD is an obstacle faced in its research and commercialization. In our previous work, we introduced a low-cost HTM, (E,E,E,E)-4,4′,4″,4‴-[Benzene-1,2,4,5-tetrayltetrakis(ethene-2,1-diyl)]tetrakis[N,N-bis(4-methoxyphenyl)aniline] (α2); however, it was immiscible in the conventional solvent chlorobenzene, leading to the adoption of dichloromethane (DCM) as an alternative. Nevertheless, its high vapor pressure led to poor reproducibility, limiting its practical applicability. To address this issue, we investigated alternative solvents to DCM to facilitate the application of α2 to dichloride alkane materials, from 1,2-dichloroethane (DCE) to 1,4-dichlorobutane. In these materials, DCE exhibits the most superior properties in terms of layer formation control, due to its vapor pressure in spin-coating. Accordingly, a PSC containing α2-DCE HTL showed high performance, with 1.15V of open-circuit voltage and a 22.7% power conversion efficiency. Full article

Two-dimensional (2D) Xenes, including graphene where X represents C, Si, Ge, and Te, represent a groundbreaking class of materials renowned for their extraordinary electrical transport properties, robust photoresponse, and Quantum Spin Hall effects. With the growing interest in 2D materials, research on germanene-based systems remains relatively underexplored despite their potential for tailored optoelectronic functionalities. Herein, we demonstrate a facile and rapid chemical synthesis of tellurium-doped germanene hydride (Te-GeH) nanostructures (NSs), achieving precise atomic-scale control. The 2D Te-GeH NSs exhibit a broadband optical absorption spanning ultraviolet (UV) to visible light (VIS), which is a critical feature for multifunctional photodetection. Leveraging this property, we engineer photoelectrochemical (PEC) photodetectors via a simple drop-casting technique. The devices deliver excellent performance, including a high responsivity of 708.5 µA/W, ultrafast response speeds (92 ms rise, 526 ms decay), and a wide operational bandwidth. Remarkably, the detectors operate efficiently at zero-bias voltage, outperforming most existing 2D-material-based PEC systems, and function as self-powered broadband photodetectors. This work not only advances the understanding of germanene derivatives but also unlocks their potential for next-generation optoelectronics, such as energy-efficient sensors and adaptive optical networks. Full article

Self-assembled monolayers (SAMs) have gained significant attention as an interfacial engineering strategy for perovskite solar cells (PSCs) due to their efficient charge transport ability and work function tunability. While solution-based methods such as dip-coating and spin-coating are widely used for SAM deposition, challenges such as non-uniform coverage, solvent contamination, and limited control over molecular orientation hinder their scalability and reproducibility. In contrast, vacuum deposition techniques, including thermal evaporation, overcome these limitations by enabling the formation of highly uniform materials with precise control over thickness and molecular arrangement. Importantly, the chemical interactions between SAM materials and perovskite layers, including coordination bonding with Pb²⁺ ions, play an important role in passivating surface defects, modulating energy levels, and promoting uniform perovskite crystallization. These interactions not only enhance wettability but also improve the overall quality and stability of perovskite films. This review highlights the advantages of vacuum-deposited SAMs, promoting strong chemical interactions with perovskite layers and improving interfacial properties critical for scalable applications. Full article

Nanostructured hybrid materials based on the combination of semiconductor QDs and GO are promising candidates for different optoelectronic and catalytic applications and being able to produce such hybrid materials in solution will expand their possible range of applications. In the current work, capping ligand-exchange procedures have been developed to replace the lead oleate normally found on the surface of PbS QDs synthesized by the popular hot-injection method. After the capping ligand-exchange process, the QDs are water soluble, which makes them soluble in most GO solutions. Solution-processed nanostructured hybrid materials based on GO flakes decorated with ligand-exchanged (EDT, TBAI and L-Cysteine) PbS QDs were synthesized by combining PbS QDs and GO solutions. Afterward, the resulting hybrid materials were thoroughly characterized by means of FTIR, XPS, Raman, UV-Vis-NIR and photoluminescence spectroscopy, as well as SEM and TEM techniques. The results indicate a clear surface chemistry variation in the capping ligand-exchanged PbS QDs, showing the presence of the exchanged ligand molecules. Thin films from the solution-processed nanostructured hybrid materials were deposited by the spin coating technique, and their optoelectronic properties were studied. Depending on the capping ligand molecule, the photoresponse and resistance of the thin films varied; the sample with the EDT ligand exchange showed the highest photoresponse and the lowest resistance. This surface chemistry had a direct effect on the charge carrier transfer and transport behavior of the nanostructured hybrid materials synthesized. These results show a novel and accessible route for synthesizing solution-processed and affordable nanostructured hybrid materials based on semiconductor QDs and GO. Additionally, the importance of the surface chemistry displayed by the PbS QDs and GO was clearly seen in determining the final optoelectronic properties displayed by their hybrid materials. Full article

A topological insulator with large bulk-insulating behavior and high electron mobility of the surface state is needed urgently, not only because it would be a good platform for studying topological surface states but also because it is a prerequisite for potential future applications. In this work, we demonstrated that tin (Sn) or indium (In) dopants could be introduced into a BiSbTeSe₂ single crystal. The impacts of the dopants on the bulk-insulating property and electron mobility of the surface state were systematically investigated by electrical transport measurements. The doped single crystals had the same crystal structure as the pristine BiSbTeSe₂, no impure phase was observed, and all elements were distributed homogeneously. The electrical transport measurements illustrated that slight Sn doping could improve the performance of BiSbTeSe₂ a lot, as the longitudinal resistivity (ρ_xx), bulk carrier density (n_b), and electron mobility of the surface state (μ_s) reached about 11 Ωcm, 7.40 × 10¹⁴ cm⁻³, and 6930 cm²/(Vs), respectively. By comparison, indium doping could also improve the performance of BiSbTeSe₂ with ρ_xx, n_b, and μ_s up to about 13 Ωcm, 1.29 × 10¹⁵ cm⁻³, and 4500 cm²/(Vs), respectively. Our findings suggest that Sn- or indium-doped BiSbTeSe₂ crystals should be good platforms for studying novel topological properties, as well as promising candidates for low-dissipation electron transport, spin electronics, and quantum computing. Full article