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The metal-free magnetism and ferromagnetic narrow gap semiconductor properties in graphene-like carbon nitride
摘要： In spintronics, if a two-dimensional (2D) organic metal-free material has stable magnetism and narrow gap semiconductor properties, it will have a very bright application prospect. A graphene-like carbon nitride (g-C13N13) that we design just meets these requirements. As a new structure, firstly the stability of the g-C13N13 has been verified. It has stable electron spin polarization and the magnetic moment of each primitive cell is 1μB. It exhibits ferromagnetic narrow gap semiconductor properties through our analysis of energy band structure and charge density. Ferromagnetic ordering between two adjacent primitive cells is stable. The Monte Carlo simulation using the Ising model shows the Curie temperature material is 204K. Our research is an inspiration for the applications of this kind of materials in spintronics devices.
关键词： Metal-free magnetism,Electron spin polarization,Ferromagnetic ordering,Narrow gap semiconductor properties,Monte Carlo simulations
更新于2025-09-10 09:29:36
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Effects of Ag Doping and Point Defect on the Magnetism of ZnO
摘要： The magnetism sources and magnetic mechanism of Ag doping and point defect, which coexist in the presence of ZnO, are frequently controversial. To solve these problems, the effects of Ag doping and Zn or O vacancy on the magnetism of ZnO were investigated using geometry optimization and energy calculation according to the first-principles generalized gradient approximation + U (GGA+U) method of density functional theory. Results revealed that the system which Ag doping and Zn vacancy coexists in ZnO could achieve room-temperature ferromagnetism. This system had an extremely high spin polarization, which was advantageous for the spin electron injection sources applied in dilute magnetic semiconductors. Result also revealed that the magnetism of Zn14AgO16 was caused by the electron hybrid coupling effects among the O-2p, Ag-4d, Ag-5s, and Zn-4s orbits. And these effects were produced by the hole carriers after complexes were formed by the Ag doping and Zn vacancy. With regard to the most stable structure of the ground state, all doping systems which Ag replacing Zn and O vacancy coexisted in ZnO and those which Ag replacing Zn, interstitial Ag, and O vacancy coexisted in ZnO were all non-magnetic. Thus, these doping systems were unsuitable for dilute magnetic semiconductors. By contrast, the doping systems of interstitial Ag and Zn vacancy were magnetic, although the magnetism was relatively weak, thus rendering such systems inapplicable as well.
关键词： Point defect,Ag doping,ZnO,Magnetism,First-principles,Vacancy
更新于2025-09-10 09:29:36
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Electrical-poling-induced strain effect in Pb(Fe0.534W0.066Nb0.4)O3
摘要： The electrical control of magnetism is a potential technique for low-energy-consuming spintronic devices. In this work, Pb(Fe0.534W0.066Nb0.4)O3 (PFWN), a known magnetoelectric-multiferroic compound, is poled using dc electric field to study the impact of induced strain on the vibrational modes and magnetism using Raman spectroscopy and magnetic susceptibility measurements, respectively. PFWN exhibits ferroelectric phase transition at TC * 300 K and antiferromagnetic ordering around TN * 187 K coinciding with an anomaly in the temperature-dependent Raman studies, indicating spin-phonon coupling. The observed changes in Raman modes and magnetization of electrically poled PFWN indicate strong converse magnetoelectric coupling effect. The electric-field-induced strain induces tilting of the FeO6 octahedra, which alters hybridization between Fe 3d and O and 2p orbitals, respectively. We present results of our studies on electric poling of PFWN in the light of current interest in the magnetic switching applications of spintronic materials.
关键词： Structure,Vibrational,Multiferroics and magnetoelectric coupling,Magnetism
更新于2025-09-10 09:29:36
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Electrophoretic Deposition Fabrication and Magnetic Manipulation of Magnetic Semiconductor Films
摘要： ZnO:Co semiconductor films were synthesized by a two-step electrophoretic deposition method. Various morphologies, including solid, crystal-grain or nanorod-array film, could be obtained by tuning the deposition conditions. Careful characterizations indicate the morphologies and structures have great effect on the magnetic and optical properties of the films. Significant difference of magnetism was investigated in the films prepared under different deposition potentials. The origination of the magnetism difference and the mechanism of the electrophoretic deposition were discussed.
关键词： Electrophoretic deposition,Magnetic semiconductor films,Nanorod arrays,Magnetism difference
更新于2025-09-09 09:28:46
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Emergent interlayer nodal superfluidity of a dipolar Fermi gas in bilayer optical lattices
摘要： Understanding the interplay between magnetism and superconductivity is one of the central issues in high-temperature superconductors. The recent experimental implementation of cold gases with highly tunable anisotropic interaction, especially in magnetic dipolar atoms or polar molecules, opens up a new thrust on exploring this interesting phenomenon. Here we report a mechanism to drive the interplay between magnetism and superfluidity through engineering the spatially anisotropic interaction via considering loading pseudospin-1/2 dipolar Fermi atoms in bilayer optical lattices. Surprisingly, we find that the weak interlayer interaction can lead to the coexistence of superfluidity and antiferromagnetism at low temperatures for the half filling case. It is distinguished from the usual scheme by doping an antiferromagnetic Mott insulating parent to access high-Tc superconductivity, where at half filling there is no coexistence of superconductivity and magnetism at low temperatures due to the absence of the superconductivity. Furthermore, the interlayer superfluid possesses an unexpected nodal structure, which is reminiscent of the nodal high-Tc superconductivity but differs in origin.
关键词： antiferromagnetism,bilayer optical lattices,dipolar Fermi atoms,superfluidity,interlayer interaction,superconductivity,magnetism,nodal structure
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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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
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Strain Induced Metal–Insulator Transition of Magnetic SrRuO3 Single Layer in SrRuO3/SrTiO3 Superlattice
摘要： Ferromagnetic phase in a two-dimensional system plays an important role not only in applications but also in studies of phase transition theory. Among numerous ferromagnetic materials, SrRuO3 is famous for its half-metallicity, itinerant ferromagnetism and non-Fermi liquid metalicity. Single layer SrRuO3 in SrRuO3/SrTiO3 (SRO/STO) superlattice has been predicted as a two-dimensional half-metallic ferromagnetic system based on density functional theory (DFT). However, experiments show that metal–insulator transition associated with ferro–antiferromagnetism (FM–AFM) transition occurs when the thickness of SRO is less than 4 u.c. Combining DFT calculations with Monte Carlo simulations, we demonstrate in this work that the bulk ferromagnetic metallicity can be realized in single layer SRO in SRO/STO superlattice by manipulating the strain effect to trigger the metal–insulator transition, achieving two-dimensional (2D) half-metallic SRO thin film beyond the experimental observation of AFM insulator.Our results pave a new route to fulfill the ultrathin spin-polarized-2D electron gas (SP-2DEG).
关键词： superlattice,metal–insulator transition,half-metal,magnetism,2DEG
更新于2025-09-04 15:30:14
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films
摘要： Noncollinear magnetism can play an important role in multiferroic materials but is relatively understudied in oxide heterostructures compared to their bulk counterparts. Using variable temperature magnetometry and neutron diffraction, we demonstrate the presence of helical magnetic ordering in CaMn7O12 and Ca1?xSrxMn7O12 (for x up to 0.51) thin ?lms. Consistent with bulk Ca1?xSrxMn7O12, the net magnetization increases with Sr doping. Neutron diffraction con?rms that the helical magnetic structure remains incommensurate at all values of x, while the fundamental magnetic wavevector increases upon Sr substitution. This result demonstrates a chemical-based approach for tuning helical magnetism in quadruple perovskite ?lms and enables future studies of strain and interfacial effects on helimagnetism in oxide heterostructures.
关键词： helical magnetism,oxide heterostructures,magnetometry,Sr-doped CaMn7O12,neutron diffraction
更新于2025-09-04 15:30:14
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Two Series of Microporous Lanthanide–Organic Frameworks with Different Secondary Building Units and Exposed Lewis Base Active Sites: Sensing, Dye Adsorption, and Magnetic Properties
摘要： Two series of new lanthanide complexes, {[Ln(L)1.5(H2O)]·DMA·4H2O}n (1-Ln, Ln = Tb, Gd, and Dy) and {[La2(L)3]·4H2O}n (2-La), were prepared successfully by Ln3+ ions and a N-heterocyclic dicarboxylic (2-pyrimidin-5-yl)terephthalic acid (H2L) ligand. The four complexes are three-dimensional (3D) microporous frameworks with different secondary building units (SBUs) and exposed Lewis base active sites. Topology analyses reveal that 1-Ln are the binodal (3,8)-connected tfz-d (43)2(46·618·84) nets and 2-La is a binodal (2,12)-connected (4)6(46·848·1212) net. The photoluminescence of 1-Tb, the dye adsorption of 1-Tb and 2-La, and the magnetism of 1-Dy have been well studied. The luminescent explorations indicate that 1-Tb is a highly efficient probe for sensing Fe3+ and Cr2O72?, respectively. Complexes 1-Tb and 2-La display the unique selective adsorption to Congo red (CR) dyes. Magnetic measurements further indicate that 1-Dy has a slow magnetic relaxation performance.
关键词： lanthanide complexes,dye adsorption,magnetism,photoluminescence,microporous frameworks,Lewis base active sites
更新于2025-09-04 15:30:14