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with pentagonal structure
摘要： Structure-property relationships have always been guiding principles for materials discovery. Here we explore the relationships to discover two-dimensional (2D) materials with the goal of identifying 2D magnetic semiconductors for spintronics applications. In particular, we report a density functional theory + U study of single-layer antiferromagnetic (AFM) semiconductor CoS2 with the pentagonal structure forming the so-called Cairo tessellation. We ?nd that this single-layer magnet exhibits an indirect band gap of 1.06 eV with electron and hole effective masses of 0.52 and 1.93 m0, respectively, which may lead to relatively high electron mobility. The hybrid density functional theory calculations correct the band gap to 2.24 eV. We also compute the magnetocrystalline anisotropy energy (MAE), showing that the easy axis of the AFM ordering is along the b axis with a sizable MAE of 153 μeV per Co ion. We further calculate the magnon frequencies at different spin-spiral vectors, based on which we estimate the N′eel temperatures to be 20.4 and 13.3 K using the mean ?eld and random phase approximations, respectively. We then apply biaxial strains to tune the band gap of single-layer pentagonal CoS2. We ?nd that the energy difference between the ferromagnetic and AFM structures strongly depends on the biaxial strain, but the ground state remains the AFM ordering. Although the low critical temperature prohibits the magnetic applications of single-layer pentagonal CoS2 at room temperature, the excellent electrical properties may ?nd single-layer semiconductor applications in optoelectronic nanodevices.
关键词： two-dimensional materials,magnon frequencies,N′eel temperature,biaxial strain,Cairo tessellation,antiferromagnetic semiconductor,density functional theory,band gap,magnetocrystalline anisotropy energy,pentagonal structure,spintronics
更新于2025-09-09 09:28:46
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Prediction of two-dimensional organic topological insulator in metal-DCB lattices
摘要： Based on first-principles calculations, we systematically investigated a two-dimensional (2D) organometallic framework consisting of metal atoms (elements from groups IIIA, IVA, VA, VIA, IB, and Pt) and dicyanobenzenes (DCBs). Our stability analysis showed that the system prefers the buckled structure in metals with p-orbital valence electrons, whereas in metals with d-orbitals, the planar phase is preferable. Topological invariants (Z2) of these systems were calculated, and they are identified as 2D intrinsic organic topological insulators. Au- and Bi-DCB are exemplar materials with the largest bandgaps within IB and VA groups. Moreover, Au-DCB exhibits robustness of its topological phase against strain. Furthermore, the topologically protected edge states in Au-DCB are identified to further verify the Z2 invariant. Interestingly, utilizing hole doping in Bi-DCB leads to a nearly flat Chern band and results in the quantum anomalous Hall phase. Our results suggest that these organometallic frameworks are promising for potential applications in quantum spintronics with the merits of low cost and ease of synthesis.
关键词： first-principles calculations,organic topological insulator,quantum spintronics,metal-DCB lattices,two-dimensional
更新于2025-09-09 09:28:46
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Effect of Synthesis Temperature on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Combustion Method
摘要： ZnO nanoparticles at different temperatures were synthesized by using the combustion method. The effect of synthesis temperature on the properties of the nanoparticles was studied by using XRD, FESEM, EDS, TEM, photoluminescence (PL), Raman, diffuse reflectance spectra (DRS), and VSM characterization techniques. The XRD results reveal that the grown nanoparticles have a hexagonal wurtzite structure without any impurities and agreed with EDS results. FESEM and TEM micrographs show that the ZnO nanoparticles possess a spherical shape with agglomeration free, and the size increases with increase of synthesis temperature. From DRS studies, it was noticed that the band gap decreases with increase of synthesis temperature. In PL studies, blue peak at 465 nm may be due to defect-related transitions. A sharp intense peak in Raman spectra at 485 cm?1 represents E2H mode is a characteristic of a hexagonal wurtzite structure. The magnetic studies show that the magnetization decreases from 0.0172 to 0.0042 emu/g as the synthesis temperature increases from 400 to 550 °C. ZnO synthesized at 500 °C has a large squareness ratio. These materials are potential candidates for memory devices.
关键词： Combustion method,Spintronics,Ferromagnetism,ZnO nanoparticles
更新于2025-09-09 09:28:46
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || In or Out of Control? Electron Spin Polarization in Spin-Orbit-Influenced Systems
摘要： Spintronics is the key word to motivate studies of spin-polarized electronic states in solids and at surfaces or interfaces. The use of the electron spin in addition to the electron charge as information carrier—that is the goal for spintronics devices. The generation, manipulation, and detection of spin-polarized currents promise applications in information technology. However, in many materials, the electronic states are spin degenerate. The spin degeneracy may be lifted by two interactions: (i) exchange interaction in magnetically ordered materials, where the magnetization direction is the reference for the alignment of the spin magnetic moments. Independent of location and momentum, the electron spin magnetic moment is either aligned parallel to the magnetization direction (majority spin, lower in energy) or antiparallel to it (minority, higher in energy), leading to a spin-dependent energy splitting, called exchange splitting, of the bands; (ii) spin–orbit interaction (SOI), which is present in all materials but becomes relevant in systems with high atomic number. In ferromagnets, SOI enables hybridization between bands of different spin character, leading to spin–orbit-induced energy gaps, sometimes called spin hot spots in the band structure, which are held responsible for demagnetization processes. Furthermore, noncollinear magnetic structures such as skyrmions arise from SOI in ferromagnets. In nonferromagnets, SOI leads to energy splitting of bands with different total angular momentum j but not necessarily to spin-split bands. Only in systems, where inversion symmetry is broken, which is, for example, the case at surfaces, the bands exhibit a spin-dependent energy splitting, which itself depends on the momentum k. This so-called Rashba-type spin splitting was predicted for a two-dimensional electron gas and experimentally observed in surface states on heavy metal surfaces, for example, Au(111) and W(110). The spin-dependent splitting depends on the momentum parallel to the surface kk and reverses its sign upon a sign change of kk. As a consequence, no net magnetic moment is formed. In contrast to Rashba systems, where surface states become spin split by SOI, topological insulators such as Bi2Se3 exhibit so-called topological surface states (TSS), which only appear as a consequence of SOI. SOI is responsible for band inversion and formation of a gap, which is then closed by a surface state with Dirac-cone-like energy dispersion and characteristic spin texture.
关键词： Rashba-type spin splitting,Spin–orbit interaction,Dirac-cone-like energy dispersion,Topological surface state,Spintronics
更新于2025-09-09 09:28:46
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Investigation of half-metallic ferromagnetism in hafnium and tantallum doped NiO for spintronic applications: A DFT study
摘要： Full Potential Linearised Augmented Plane Wave (FP-LAPW) method was used to investigate the electronic and magnetic properties of NiO doped with Hf and Ta within the frame work of density functional theory(DFT). NiO is found to be stable in rock salt structure. NiO shows metallic character for the lattice constant of 4.155?. Doping Hf and Ta in the metallic super cell of NiO separately in the doping concentration of 12.5%, the compounds Hf0.125Ni0.875O and Ta0.125Ni0.875O are formed. These compounds of Hf0.125Ni0.875O and Ta0.125Ni0.875O are found to be stable in the ferromagnetic phase. The density of states and band structure plots predict that these compounds exhibit half metallic character with formation of energy gap in one of the spins at the Fermi level. The total spin magnetic moments found in these compounds are 12.00689 μB and 10.97628 μ B.
关键词： DFT,Hf and Ta doping,spintronics,Half-metallic ferromagnetism,NiO
更新于2025-09-09 09:28:46
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Raman fingerprint of two terahertz spin wave branches in a two-dimensional honeycomb Ising ferromagnet
摘要： Two-dimensional (2D) magnetism has been long sought-after and only very recently realized in atomic crystals of magnetic van der Waals materials. So far, a comprehensive understanding of the magnetic excitations in such 2D magnets remains missing. Here we report polarized micro-Raman spectroscopy studies on a 2D honeycomb ferromagnet CrI3. We show the definitive evidence of two sets of zero-momentum spin waves at frequencies of 2.28 terahertz (THz) and 3.75 THz, respectively, that are three orders of magnitude higher than those of conventional ferromagnets. By tracking the thickness dependence of both spin waves, we reveal that both are surface spin waves with lifetimes an order of magnitude longer than their temporal periods. Our results of two branches of high-frequency, long-lived surface spin waves in 2D CrI3 demonstrate intriguing spin dynamics and intricate interplay with fluctuations in the 2D limit, thus opening up opportunities for ultrafast spintronics incorporating 2D magnets.
关键词： micro-Raman spectroscopy,CrI3,spintronics,2D magnetism,spin waves
更新于2025-09-09 09:28:46
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Epitaxial growth of Sb-doped Ge layers on ferromagnetic Fe <sub/>3</sub> Si for vertical semiconductor spintronic devices
摘要： By combining solid phase epitaxy and molecular beam epitaxy with Sb doping, we can form n-type Ge layers on one of the ferromagnetic Heusler alloys, Fe3Si. Two-dimensional epitaxial growth of the Sb-doped Ge layers can be achieved on the Si-terminated Fe3Si surface at 175 ?C. Electrical properties of the Au-Ti/Sb-doped Ge/Fe3Si/p-Ge/Al vertical devices indicate that the Sb-doped Ge layer is an n-type semiconductor. We also show a high-quality CoFe/n-Ge/Fe3Si trilayer structure for vertical semiconductor spintronic devices.
关键词： germanium,solid phase epitaxy,molecular beam epitaxy,spintronics
更新于2025-09-09 09:28:46
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Vector-Resolved Magnetooptic Kerr Effect Measurements of Spin-Orbit Torque
摘要： We demonstrate simultaneous detection of current-driven dampinglike and fieldlike spin–orbit torques in heavy metal/ferromagnetic metal bilayers by measuring all three magnetization components mx, my, and mz using a vector-resolved magnetooptic Kerr effect (MOKE) technique based on quadrant detection. We investigate the magnitude and direction of spin–orbit torques in a series of platinum/permalloy samples, finding good agreement with results obtained via polar and quadratic MOKE measurements without quadrant detection.
关键词： Magneto-optic effects,spintronics
更新于2025-09-09 09:28:46
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Physical nature of electrically detected magnetic resonance through spin dependent trap assisted tunneling in insulators
摘要： We show that electrically detected magnetic resonance (EDMR), through spin dependent trap assisted tunneling (SDTT) in amorphous SiC, exhibits approximately equal amplitudes at very high (8.5 T) and very low (0.013 T) magnetic fields at room temperature. This result strongly supports an SDTT/EDMR model in which spins at two nearby sites involved in a tunneling event are coupled for a finite time in circumstances somewhat analogous to spin pair coupling in the spin dependent recombination/EDMR model of Kaplan, Solomon, and Mott (KSM) [Kaplan, Solomon, and Mott, J. Phys. Lett. 39, 51 (1978)]. Since a comparable near zero magnetic field change in resistance is also observed in these samples, our results support the idea that this magnetoresistance response is also the result of a KSM-like mechanism involving SDTT. Additionally, we observe a large enhancement in SDTT/EDMR at high field (8.5 T) for temperatures below 50 K, which suggests the potential utility of SDTT in spin based quantum computation and other spintronic applications.
关键词： spin dependent trap assisted tunneling,electrically detected magnetic resonance,spintronics,amorphous SiC,magnetoresistance
更新于2025-09-04 15:30:14
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Charge and spin transport anisotropy in nanopatterned graphene
摘要： Anisotropic electronic transport is a possible route towards nanoscale circuitry design, particularly in two-dimensional materials. Proposals to introduce such a feature in patterned graphene have to date relied on large-scale structural inhomogeneities. Here we theoretically explore how a random, yet homogeneous, distribution of zigzag-edged triangular perforations can generate spatial anisotropies in both charge and spin transport. Anisotropic electronic transport is found to persist under considerable disordering of the perforation edges, suggesting its viability under realistic experimental conditions. Furthermore, controlling the relative orientation of perforations enables spin ?ltering of the transmitted electrons, resulting in a half-metallic anisotropic transport regime. Our ?ndings point towards a co-integration of charge and spin control in a two-dimensional platform of relevance for nanocircuit design. We further highlight how geometrical effects allow ?nite samples to display ?nite transverse resistances, reminiscent of Spin Hall effects, in the absence of any bulk ?ngerprints of such mechanisms, and explore the underlying symmetries behind this behaviour.
关键词： zigzag edge magnetism,antidots,perforations,spintronics,anisotropic transport,graphene,spin splitting
更新于2025-09-04 15:30:14