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Investigation of Structural and Elastic Stability, Electronic, Magnetic, Thermoelectric, Lattice-Dynamical and Thermodynamical Properties of Spin Gapless Semiconducting Heusler Alloy Zr2MnIn Using DFT Approach
摘要： In recent times, spin gapless semiconductors (SGS) have attracted much attention as a promising candidate for spintronics and thermoelectric applications due to their high carrier concentration and good thermoelectric figure of merit. In this paper, we have carried out a systematic theoretical investigation of the structural, elastic, thermal, electronic, magnetic, thermoelectric, lattice dynamical and thermodynamical properties of Zr2MnIn using density functional theory (DFT) based first principle calculations. The band structure calculation shows indirect band gap in a spin down channel and zero band gap in a spin up channel of valence and conduction bands confirming the spin gapless semiconducting nature of Zr2MnIn. The structural and dynamical stability of the antiferromagnetic phase of Zr2MnIn has also been investigated. Magnetization in Zr2MnIn originates due to the d state electrons of Zr atoms, which follows the Slater Pauling rule: Mt = Zt (cid:2) 18. Phonon dispersion curves exhibit real frequency of phonon modes throughout the Brillouin zone, which confirms the dynamical stability of the antiferromagnetic phase of Zr2MnIn. Thermodynamical properties including specific heat and Debye temperature have been calculated using phonon density of states. A higher value of the thermoelectric figure of merit 1.25, predicts that this alloy as good thermoelectric properties with better output efficiency.
关键词： Spin gapless semiconductor (SGS),magnetic moment,structural and elastic stability,thermoelectric and lattice dynamical properties,electronic structure
更新于2025-09-23 15:23:52
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Functionalized Single-Atom-Embedded Bilayer Graphene and Hexagonal Boron Nitride
摘要： Single-atom-embedded bilayer graphene and two-dimensional hexagonal boron nitride are proposed in terms of first-principles calculations. In particular, a series of 68 different single atoms are embedded within bilayer graphene and boron nitride. It is revealed that the magnetic moment and bandgap behave differently depending on the atomic element used for doping where it becomes possible to form a magnet, conductor, semiconductor, or insulator. The electronic and geometrical properties of bilayer graphene and boron nitride are, in principle, able to be tailored and tuned, thereby expanding on how two-dimensional materials are functionalized and designed.
关键词： single atom,boron nitride,bandgap,graphene,functionalized graphene,magnetic moment
更新于2025-09-23 15:23:52
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Density functional theory study of aluminium and chromium doped Yttrium ion garnet
摘要： Density functional theory has been performed to investigate the atomic structure, electronic and magnetic properties of Al3+ and Cr3+ co-doped cubic Y3Fe5O12 (YIG) garnet crystal. Results show that Al3+ and Cr3+ ions are energetically substitution of Fe3+ at the tetrahedral and octahedral sites in YIG, respectively. The doping concentration do not affect the preferential site occupancy for separate individual substitution. The magnetic moment increases and decreases for the single Cr and Al element doping, respectively. The magnetic moment and lattice constant decreases with the increase of Al–Cr concentrations. The magnetic moment decrease from 5.0 to 3.875 μB linearly with x increases from 0 to 0.4 in Y3AlxCrxFe5?xO12. These results indicate that doping can be adopted for the modi?cation of magnetic properties of YIG.
关键词： doping,magnetic moment,density functional theory,Y3Fe5O12 (YIG)
更新于2025-09-23 15:23:52
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Decreased Energy Gap and Enhanced Conductivity in Zn-Doped Sr2IrO4
摘要： The 5d transition metal oxide Sr2IrO4 has attracted much interest in the high-temperature superconductivity community since it highly resembles the cuprate superconductor in crystal and electronic structures. Here, we report on the transport and magnetic properties of Zn-doped Sr2IrO4. It is found that the energy gap of Sr2IrO4 is rapidly decreased with a small amount of Zn doping. Consequently, the electrical conductivity is significantly enhanced. The present work could serve as the prerequisite stage in exploring the possible superconductivity of the Sr2IrO4 compound.
关键词： Energy gap,Magnetic moment,Sr2IrO4
更新于2025-09-23 15:22:29
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Observation of Optical Band-Gap Narrowing and Enhanced Magnetic Moment in Co-Doped Sol–Gel-Derived Anatase TiO <sub/>2</sub> Nanocrystals
摘要： The magnetic behavior of TiO2 and doped TiO2 nanocrystals has been a challenge due to the unambiguous nature of defects present in oxide semiconductors. Here, a simple, low-temperature sol?gel method is developed for the synthesis of low-dimensional and highly efficient stable anatase TiO2 nanocrystals. The X-ray powder diffraction pattern and Raman spectra confirm the formation of a single-phase anatase structure of TiO2. High-resolution transmission electron microscopy studies reveal the crystalline nature of the sol?gel-derived nanocrystals. The increase in lattice parameters together with the shifting and broadening of the most intense Eg(1) mode in micro-Raman spectra of Co-doped TiO2 nanocrystals indicate the incorporation of Co in TiO2. Shifting of the absorption edge to the visible region in UV?visible spectra indicates narrowing of the band gap due to Co incorporation in TiO2. X-ray photoelectron spectra confirm the presence of Co2+ and Co3+ in Co-doped TiO2 samples. Oxygen vacancy defects lead to the formation of bound magnetic polarons which induces a weak ferromagnetic behavior in air-annealed 3% Co-doped TiO2 at room temperature. It is observed that irrespective of the dopant ion, whether magnetic or nonmagnetic, the overlapping of bound magnetic polarons alone can induce ferromagnetism, while the magnetic impurities give rise to an enhanced paramagnetic moment for higher Co concentrations. A detailed understanding on the variation of these magnetic properties by estimating the concentration of bound magnetic polarons is presented, which is in corroboration with the photoluminescence studies. The observed band-gap narrowing in Co-doped TiO2 nanostructures and the mechanism underlying the magnetic interactions associated with the magnetic impurity concentration are advantageous from an applied perspective, especially in the field of spintronic and magneto-optic devices.
关键词： spintronic,magnetic moment,nanocrystals,optical band-gap narrowing,TiO2,magneto-optic devices,Co-doped,sol?gel
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Development of the theoretical basis of magnetic measurement uncertainty evaluation
摘要： The theoretical foundations of measurement uncertainty evaluation magnetic moment of radio electronic means using point methods are considered. A sequence and implementation of the uncertainty assessment procedure is proposed. A model equation based on the multipole description of the object’s magnetic field is obtained. An analysis of the equation is made. The uncertainty budget has been drawn up. Found standard and extended uncertainty. The results are in demand for control procedures and tests in the area of technical magnetism. The results contribute to the standardization of the quality assessment of magnetic measurements.
关键词： external magnetic field,dipole magnetic moment,induction sensor,measurement uncertainty
更新于2025-09-23 15:19:57
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Engineering Point Defect States in Monolayer WSe <sub/>2</sub>
摘要： Defect engineering is a key approach for tailoring the properties of the emerging two-dimensional semiconductors. Here, we report an atomic engineering of the W vacancy in monolayer WSe2 by single potassium atom decoration. The K decoration alters the energy states and reshapes the wave-function such that previously hidden mid-gap states become visible with well-resolved multiplets in scanning tunneling spectroscopy. Their energy levels are in good agreement with first principle calculations. More interestingly, the calculations show that an unpaired electron donated by the K atom can lead to a local magnetic moment, exhibiting an on-off switching by the odd-even number of electron filling. Experimentally the Fermi level is pinned above all defect states due to the graphite substrate, corresponding to an off state. The close agreement between theory and experiment in the off state, on the other hand, suggest a possibility of gate-programmable magnetic moments at the defects.
关键词： mid-gap defect states,spin splitting,defect engineering,local magnetic moment,transition metal dichalcogenides
更新于2025-09-19 17:15:36
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Exact ground state solution of shallow hydrogenic impurity states of a spherical parabolic GaAs/InAs quantum dot
摘要： The ground state spin magnetic moment current, binding energy, wave function and diamagnetic susceptibility of a shallow hydrogenic impurity located at the center of a parabolic spherical quantum dot are calculated analytically as a function of the dot size, interaction strength and confinement frequency. For comparison purposes, the results are discussed in the presence and in the absence of an impurity. Also, the dependence of the spin magnetic moment current on the spherical coordinates are derived, it is found that the spin magnetic moment current exhibits a peak structure and this current has a pronounced maximum for both small dot sizes and in the absence of impurities. Our results show that the impurities ground state binding energy enhances as the dot dimension decreases and depends strongly on the interaction strength as the dot size increases and reduces to zero in the bulk limit for large dimension of the dot. Moreover, the harmonic interaction has a strong influence on the diamagnetic susceptibility when the dot size increases where it decreases sharply in the presence of impurities while in the absence of impurities it decreases smoothly. In addition, the intensity of the magnetic field created by the spin magnetic moment current at the center of the quantum dot has been calculated. It is concluded that there is a critical value for characteristic parameters and the dot size for each type of semiconductor QD to give a specific function that might be important for nanotechnology manufacturing techniques.
关键词： Spherical quantum dot,Diamagnetic susceptibility,Harmonic e-e interaction,Donor impurity,Spin magnetic moment current
更新于2025-09-19 17:13:59
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Confinement-Induced Giant Spin-Orbit-Coupled Magnetic Moment of Co Nanoclusters in TiO2 Films
摘要： High magnetization materials are in great demand for the fabrication of advanced multifunctional magnetic devices. Notwithstanding this demand, the development of new materials with these attributes has been relatively slow. In this work, we propose a new strategy to achieve high magnetic moments above room temperature. Our materials engineering approach invoked the embedding of magnetic nanoclusters in an oxide matrix. By precisely controlling pulsed laser deposition parameters, Co nanoclusters are formed in a 5 at.% Co-TiO2 film. The presence of these nanoclusters was confirmed using transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray absorption fine structure. The film exhibits a very high saturation magnetization of 99 emu/cm3. Detailed studies using X-ray magnetic circular dichroism confirm that Co has an enhanced magnetic moment of 3.5 μB/atom, whilst the Ti and O also contribute to the magnetic moments. First principles calculations supported our hypothesis that the metallic Co nanoclusters surrounded by a TiO2 matrix can exhibit both large spin and orbital moments. Moreover, a quantum confinement effect results in a high Curie temperature for the embedded Co nanoclusters. These findings reveal that 1-2 nm nanoclusters that are quantum confined can exhibit very large magnetic moments above room temperature, representing a promising advance for the design of new high magnetization materials.
关键词： TiO2,Quantum,Ferromagnetism,Enhanced magnetic moment,Confinement effect,Nanoclusters
更新于2025-09-11 14:15:04
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Atomic ordering, magnetic properties, and electronic structure of Mn<sub>2</sub>CoGa Heusler alloy
摘要： The magnetic properties and atomic arrangement of Mn2CoGa Heusler alloy were investigated experimentally and by theoretical calculations. The magnetic moment derived from spontaneous magnetization at 5 K was 2.06 μB/f.u. and was close to the integer number of the expected value from theoretical calculation and the Slater–Pauling rule predicted by Galanakis et al. The Curie temperature and L21-B2 order-disorder phase transition temperature were 741 and 1047 K, respectively. Powder neutron diffraction experiment results suggested that the atomic arrangement prefers an L21b-type structure rather than that of Hg2CuTi, being consistent with our previous results of high-angle annular dark-field-scanning transmission electron microscopic observations. The magnetic moments obtained were in good agreement with the theoretical values in the model of the L21b-type structure. The density of states obtained by the first-principles calculation combined with the coherent potential approximation in Mn2CoGa with the L21b-type crystal structure maintained the half-metallic character, even though disordering by Mn and Co atoms was introduced.
关键词： powder neutron diffraction,magnetic moment,Half-metal-type ferromagnets,order-disorder phase transition,atomic ordering,Curie temperature
更新于2025-09-09 09:28:46