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Investigation of Fe-doped room temperature dilute magnetic ZnO semiconductors
摘要： Different ceramics sample of Zn1-xFexO (ZFO) series have been sintered by solid state reaction method. Single phase polycrystalline Fe-doped ZnO sample with hexagonal wurtzite structure has been obtained with x < 0.03 mol. Segregation of Fe and/or its oxides have not been found in the XRD patterns. A weak secondary phase of ZnFe2O4 has been detected with x ≥ 0.03 mol. Presence of Ohmic conductivity has been detected in the dielectric property analysis and the reasons for this Maxwell-Wagner-Sillars (MWS) relaxation has been explained by the grain boundary barrier defect (GBBD) process. The obtained shift of diamagnetic behavior of pure ZnO samples to para-magnetic for ZFO samples has been established with the defect and impurity structure. The band gap energy for ZFO samples has been calculated between 2.85 eV to 3.15 eV. The results indicate the potential use of Fe doped ZnO ceramics in high frequency device applications.
关键词： Spintronics,XRD,Hysteresis loops,Dilute magnetic semiconductor,Dielectric constant,Optical property
更新于2025-10-22 19:40:53
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Spatial Separation of Carrier Spin by the Valley Hall Effect in Monolayer WSe <sub/>2</sub> Transistors
摘要： We investigate the valley Hall effect (VHE) in monolayer WSe2 field-effect transistors using optical Kerr rotation measurements at 20 K. While studies of the VHE have so far focused on n-doped MoS2, we observe the VHE in WSe2 in both the n- and p-doping regimes. Hole doping enables access to the large spin-splitting of the valence band of this material. The Kerr rotation measurements probe the spatial distribution of the valley carrier imbalance induced by the VHE. Under current flow, we observe distinct spin-valley polarization along the edges of the transistor channel. From analysis of the magnitude of the Kerr rotation, we infer a spin-valley density of 44 spins/μm, integrated over the edge region in the p-doped regime. Assuming a spin diffusion length less than 0.1 μm, this corresponds to a spin-valley polarization of the holes exceeding 1%.
关键词： magneto-optical Kerr effect,Tungsten diselenide,valleytronics,spintronics
更新于2025-09-23 15:23:52
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Non-Equilibrium Green's Function based Circuit Models for Coherent Spin Devices
摘要： With recent developments in spintronics, it is now possible to envision 'spin-driven' devices with magnets and interconnects that require a new class of transport models using generalized Fermi functions and currents, each with four components: one for charge and three for spin. The corresponding impedance elements are not pure numbers but 4 × 4 matrices. Starting from the Non-Equilibrium Green's Function (NEGF) formalism in the elastic, phase-coherent transport regime, we develop spin generalized Landauer-Büttiker formulas involving such 4 × 4 conductances, for multi-terminal devices in the presence of Normal-Metal (NM) leads. In addition to usual 'terminal' conductances describing currents at the contacts, we provide 'spin-transfer torque' conductances describing the spin currents absorbed by ferromagnetic (FM) regions inside the conductor, specifying both of these currents in terms of Fermi functions at the terminals. We derive universal sum rules and reciprocity relations that would be obeyed by such matrix conductances. Finally, we apply our formulation to two example Hamiltonians describing the Rashba and the Hanle effect in 2D. Our results allows the use of pure quantum transport models as building blocks in constructing circuit models for complex spintronic and nano-magnetic structures and devices for simulation in SPICE-like simulators.
关键词： Rashba effect,spintronics,Landauer-Büttiker formula,spin-transfer torque,Non-Equilibrium Green's Function,Hanle effect,SPICE simulation
更新于2025-09-23 15:23:52
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Single spin localization and manipulation in graphene open-shell nanostructures
摘要： Turning graphene magnetic is a promising challenge to make it an active material for spintronics. Predictions state that graphene structures with specific shapes can spontaneously develop magnetism driven by Coulomb repulsion of π-electrons, but its experimental verification is demanding. Here, we report on the observation and manipulation of individual magnetic moments in graphene open-shell nanostructures on a gold surface. Using scanning tunneling spectroscopy, we detect the presence of single electron spins localized around certain zigzag sites of the carbon backbone via the Kondo effect. We find near-by spins coupled into a singlet ground state and quantify their exchange interaction via singlet-triplet inelastic electron excitations. Theoretical simulations picture how electron correlations result in spin-polarized radical states with the experimentally observed spatial distributions. Extra hydrogen atoms bound to radical sites quench their magnetic moment and switch the spin of the nanostructure in half-integer amounts. Our work demonstrates the intrinsic π-paramagnetism of graphene nanostructures.
关键词： scanning tunneling spectroscopy,graphene,Kondo effect,magnetism,spintronics
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - FANTASI: A Novel Devices-to-Circuits Simulation Framework for Fast Estimation of Write Error Rates in Spintronics
摘要： Though physical mechanisms such as spin-transfer torque (STT), spin-orbit torque (SOT), and voltage-controlled magnetic anisotropy (VCMA) has potential to enable energy-efficient and ultra-fast switching of spintronic devices, the switching dynamics are stochastic due to thermal fluctuations. Thus, there is a need in spintronics to understand the interactions between circuit design and the error rate in the switching mechanism, called as write error rate. In this paper, we propose a novel devices-to-circuits simulation framework (FANTASI) for fast estimation of the write error rates (WER) in different spintronic devices and circuits. Here, we show that, FANTASI enables efficient spintronic device-circuit co-design, with results in good agreement with the experimental measurements.
关键词： Fokker-Planck equation,spin-orbit torque,Spin-transfer torque,voltage-controlled magnetic anisotropy,spintronics
更新于2025-09-23 15:22:29
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Electroburning of few-layer graphene flakes, epitaxial graphene, and turbostratic graphene discs in air and under vacuum
摘要： Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we report a systematic characterization of the electroburning (EB) process, leading to the formation of nanometer-spaced gaps, on different types of few-layer graphene (namely mechanically exfoliated graphene on SiO2, graphene epitaxially grown on the C-face of SiC and turbostratic graphene discs deposited on SiO2) under air and vacuum conditions. The EB process is found to depend on both the graphene type and on the ambient conditions. For the mechanically exfoliated graphene, performing EB under vacuum leads to a higher yield of nanometer-gap formation than working in air. Conversely, for graphene on SiC the EB process is not successful under vacuum. Finally, the EB is possible with turbostratic graphene discs only after the creation of a constriction in the sample using lithographic patterning.
关键词： graphene,graphene based electrodes,molecular electronics,molecular spintronics
更新于2025-09-23 15:22:29
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Millimeter-sized magnetic domains in perpendicularly magnetized ferrimagnetic Mn <sub/>4</sub> N thin films grown on SrTiO <sub/>3</sub>
摘要： The use of epitaxial layers for domain wall-based spintronic applications is often hampered by the presence of pinning sites. Here, we show that when depositing Mn4N (10 nm) epitaxial films, the replacement of MgO(001) by SrTiO3(001) substrates allows minimizing the misfit, and to obtain an improved crystalline quality, a sharper switching, a full remanence, a high anisotropy and remarkable millimeter-sized magnetic domains, with straight and smooth domain walls. In a context of rising interest for current-induced domain wall motion in rare-earth ferrimagnets, we show that Mn4N/SrTiO3, which is rare-earth free, constitutes a very promising ferrimagnetic system for current-induced domain wall motion.
关键词： domain wall motion,Mn4N,ferrimagnetic,spintronics,SrTiO3
更新于2025-09-23 15:21:21
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Fano-resonant Excitations of Generalized Optical Spin Waves
摘要： While chiral materials possess spin-form wave functions as their eigenmodes, optical spin excitations cannot be obtained solely in chiral materials due to a lack of spin impedances. To date, spin excitation has generally been induced through non-conservative methods, such as circular dichroism or magneto-optical effects. In this chapter, we describe a conservative approach to optical spin excitation and control based on the spin-dependent appearance of Fano resonance. Starting from the development of the spin-form temporal coupled mode theory for 2D and 3D chiral resonances, the origin of the spin-Fano interactions is demonstrated in terms of the link between the spin eigenmodes in the polarization domain and anti-symmetric Fano resonances in the spectral domain. By comparing this spin-dependent Fano-resonant system with other optical spin materials, such as chiral, circular dichroic, and birefringent media, we discuss the impact of our results toward the realization of optical spintronics, such as applications of highly selective spin switching and unpolarized spinning operations.
关键词： Fano resonance,chiral materials,temporal coupled mode theory,optical spin,spintronics
更新于2025-09-23 15:21:21
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Room temperature spin injection into SiC via Schottky barrier
摘要： Electrical spin injection into and spin extraction from a wide-bandgap semiconductor SiC at room temperature were demonstrated via Schottky junctions. The spin relaxation time of SiC could reach 300 ps, overwhelming that of Si with similar carrier density due to the smaller atomic number. We also found that there existed two channels in SiC/CoFeB Schottky junctions for spin relaxation, one from bulk SiC and the other from interfacial defect states within the barrier whose spin relaxation times were about 1 ns. The bias condition controlled transport channels via bulk or defect states within the barrier and then affected the effective spin relaxation process. Realization of spin injection into SiC shed light on spintronics of wide-bandgap semiconductors such as spin-resolved blue light emitting diodes and high power/temperature spintronics.
关键词： spintronics,SiC,spin injection,Schottky barrier,wide-bandgap semiconductor
更新于2025-09-23 15:21:21
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Unprecedented charge state control in graphene quantum dots
摘要： High-quality double quantum dots in bilayer graphene are realized with controlled charge down to one electron. These devices provide a promising basis for spin-based qubits with long spin lifetimes.
关键词： Quantum dots,graphene,spintronics,quantum information
更新于2025-09-23 15:21:01