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Nanoparticles-assembled ZnFe2O4 mesoporous nanorods for physicochemical and magnetic properties
摘要： Hierarchically one dimensional (1-D) mesoporous ZnFe2O4 rods with nanoparticles as their building blocks have been synthesized by the solvothermal approach. The influence of annealing temperature on structural, morphological, optical and magnetic properties was intensively investigated. X-ray diffraction was used to ascertain the phase purity of synthesized samples. To perceive the information on morphological and structural features, field emission scanning electron microscopy and high resolution transmission electron microscopy with energy dispersive spectroscopy was probed. It was observed that nanorods with high aspect ratio were obtained when treated at 600 °C (ZF600) annealing temperature as compared to 400 °C (ZF400). Fourier transform infra-red spectroscopy was resorted to gain the insight of bonding mechanism associated with ZF400 and ZF600. To enrich the study on material chemistry and defects, Raman spectroscopy and X-ray photoelectron spectroscopy was performed. Brunauer–Emmett–Teller envisioned the surface area of ZF400 and ZF600. It was found that surface area decreases with increase in annealing temperature. UV–Vis spectroscopy expounds that the optical band gap increases with annealing temperature from 3.0 to 3.3 eV for ZF400 to ZF600 respectively. Magnetic measurements were performed on vibrating sample magnetometer at room temperature and the results decipher the superparamagnetic nature of the synthesized material. Additionally, saturation magnetization was found to increase with annealing temperature.
关键词： optical properties,nanorods,ZnFe2O4,solvothermal,magnetic properties,annealing
更新于2025-09-11 14:15:04
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Impact of a topological defect and Rashba spin-orbit interaction on the thermo-magnetic and optical properties of a 2D semiconductor quantum dot with Gaussian confinement
摘要： In this paper, we examine the effect of introducing a conical disclination on the thermal and optical properties of a two dimensional GaAs quantum dot in the presence of a uniform and constant magnetic field. In particular, our model consists of a single-electron subject to a confining Gaussian potential with a spin-orbit interaction in the Rashba approach. We compute the specific heat and the magnetic susceptibility from the exact solution of the Schr?dinger equation via the canonical partition function, and it is shown that the peak structure of the Schottky anomaly is linearly displaced as a function of the topological defect. We found that such defect and the Rashba coupling modify the values of the temperature and magnetic field in which the system behaves as a paramagnetic material. Remarkably, the introduction of a conical disclination in the quantum dot relaxes the selection rules for the electronic transitions when an external electromagnetic field is applied. This creates a new set of allowed transitions causing the emergence of semi-suppressed resonances in the absorption coefficient as well as in the refractive index changes which are blue-shifted with respect to the regular transitions for a quantum dot without the defect.
关键词： Rashba spin-orbit interaction,optical properties,thermo-magnetic properties,topological defect,2D semiconductor quantum dot,Gaussian confinement
更新于2025-09-11 14:15:04
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Supramolecular structures of terbium( <scp>iii</scp> ) porphyrin double-decker complexes on a single-walled carbon nanotube surface
摘要： This work mainly reports the observation of novel supramolecular structures of TbIII-5,15-bisdodecylporphyrin (BDP, C12P) double-decker complexes on the surfaces of single-walled carbon nanotubes (SWNTs) performed by scanning tunneling microscopy under an ultra-high vacuum and low temperature, atomic force microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, and ultraviolet-visible spectroscopy. The molecules formed a well-ordered self-assembled helix-shaped array with regular periodicity on the tube surface. Additionally, some magnetic properties of the BDP-molecule as well as the resulting BDP-SWNT composites were investigated by superconducting quantum interference measurements. The molecule exhibits single-molecule magnetic (SMM) properties and the composite's magnetization increases almost linearly with decreasing temperature which is possibly due to the coupling between porphyrin molecules and SWNTs. Consequently, this may enable the development of more advanced spintronic devices based on porphyrin-nanocarbon composites.
关键词： Scanning tunneling microscopy,Magnetic properties,Supramolecular structures,Single-walled carbon nanotube,Atomic force microscopy,Terbium(III) porphyrin
更新于2025-09-11 14:15:04
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Influence of the Cation on the Surface Electronic Band Structure and Magnetic Properties of Mn:ZnS and Mn:CdS Quantum Dot Thin Films
摘要： The effects of doping Mn into ZnS and CdS quantum dots are reported. Scanning tunneling spectroscopy spectra show a reduction in the electronic band gap in both CdS and ZnS upon incorporation of the Mn dopant. Mn:ZnS exhibits a rigid band shift toward higher bias which is reminiscent of a hole doping effect. This rigid band shift in Mn:ZnS is argued, with the help of X-ray photoelectron spectroscopy, to be due to a hole-doping mechanism caused by the favorable formation of Zn vacancies and a reduction in S vacancies compared to undoped ZnS films. In CdS no rigid band shift is observed even though the presence of Cd vacancies can be confirmed by photoemission and magnetic measurements. A strong sp-d hybridization is observed in the Mn:CdS film upon introducing the Mn dopant. d0 ferromagnetism is observed in both undoped ZnS and CdS quantum dot thin films at room temperature. Upon doping of Mn into ZnS the magnetization is reduced suggesting an antiparallel alignment of Mn-Mn or Mn-Zn vacancies nearest neighbors. Density Functional Theory supports the experimental results indicating the nearest neighbor Mn atoms prefer antiparallel alignment of their magnetic moments with preferred ground state of Mn in 3+ oxidation state.
关键词： CdS,Mn doping,quantum dots,magnetic properties,scanning tunneling spectroscopy,electronic band structure,X-ray photoelectron spectroscopy,density functional theory,ZnS
更新于2025-09-11 14:15:04
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Studies on structural, optical and magnetic properties of (Ru, Mn) codoped ZnO nanostructures
摘要： Ruthenium and manganese codoped ZnO (RuxMn0.01Zn0.99-xO; x = 0.01, 0.02 and 0.03) were synthesized by sol-gel method via ultrasonication. The effects of codoping on structural, microstructural, optical and magnetic properties of the as-synthesized materials were characterized through X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and SQUID magnetometer, respectively. From the XRD pattern, it is evident that all the diffraction peaks can be indexed to the hexagonal wurtzite structure and shows the incorporation of dopants ie. Ru and Mn are substituted in the ZnO lattice. Nanosphere like morphology was observed in HRTEM analysis and the average particle sizes are found to be 20-30 nm, which are good agreement with the XRD crystallite size by Scherrer formula. Photoluminescence (PL) studies were carried out to investigate the optical properties of the as-synthesized materials and the defects related strong green emission peaks was observed in the TM codoped ZnO samples. It can be clearly seen from SQUID results, the loop is linear with the field indicating the presence of paramagnetism / anti ferromagnetism in the samples.
关键词： ZnO,sol-gel,optical properties,codoping,ultrasonication,magnetic properties,structural properties
更新于2025-09-10 09:29:36
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Ferromagnetism induced by vacancies in (N, Al)-codoped 6H-SiC
摘要： The electronic structures and magnetic properties of 6H-SiC doped with N, C vacancies (VC), Si vacancies (VSi) and Al are studied by first principles calculations. The results indicate that the N substituting C in 6H-SiC cannot order magnetism but VSi can introduce magnetic moments effectively. Ferromagnetism coupling is obtained in (N, 2VSi)-codoped 6H-SiC. The ferromagnetism can be mainly attributed to the interactions between the 2p orbitals of C atoms around Si vacancies. More interestingly, substituting Si with Al can enhance the ferromagnetic states in 6H-SiC. We also studied the effect of charge on magnetic properties and provide an effective method of tuning magnetism in 6H-SiC.
关键词： First principles,Electronic structure,Dilute magnetic semiconductors,6H-SiC,Magnetic properties
更新于2025-09-10 09:29:36
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Physical properties of fluorides barium and calcium nanopowders produced by the pulsed electron beam evaporation method
摘要： The mesoporous nanocrystal powders BaF2 and CaF2 with a specific surface up to 34.8 and 88.7 sq.m/g, respectively, are produced by the pulsed electron beam evaporation method in vacuum. The influence of thermal annealing of nanoparticles on air in the range of temperature from 200 to 900°C on the size, morphology of particles and change of their magnetic and luminescent properties investigated have been investigared. The essential stoichiometric impurity (overage of metals) and significant growth in a specific surface of nanopowders (NP) BaF2 and CaF2 after annealing at the temperature of 200°C have been detected. It is established that the synthesized NP BaF2 is a paramagnetic while initial material in the bulk state is diamagnetic. After annealing at 900°C appears the small ferromagnetic contribution at NP BaF2. Produced NP CaF2 showed ferromagnetic behavior. In literature there is no information about the ferromagnetism of CaF2. Appearance of the ferromagnetic response can be explained with formation of structural and radiation defects (F-centers, etc.). The analysis of PCL and magnetization curves of samples BaF2 and CaF2 allows drawing conclusions about their connection.
关键词： CaF2,pulsed electron beam evaporation,magnetic properties,luminescent properties,nanopowders,BaF2
更新于2025-09-10 09:29:36
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Structural, optical and magnetic properties of YIG and TbErIG nanofilms prepared using a sol-gel method
摘要： A series of yttrium iron garnet (YIG) and terbium erbium iron garnet (TbErIG) nanocrystalline films were successfully grown using a sol-gel method. A crystalline analysis carried out using an X-ray diffractometer confirmed that all films had a single-phase garnet structure. The TbErIG films annealed in O2 and Ar gas had a larger number of crystallisation peaks, with a lattice constant that was close to the standard value for ErIG. The transparency increased from 94% for YIG (O2) to 98% for TbErIG (O2) films in the near-infrared region. All films were soft ferrite materials, as indicated by their magnetic hysteresis loops. The value of saturated magnetisation was increased for samples annealed in air, and was markedly decreased for samples subjected to O2 and Ar atmospheres. An increase in the coercivity value (91 Oe) was also observed for the TbErIG (Ar) film. YIG and TbErIG showed a phase transition from ferrimagnetic to paramagnetic at the Curie temperature, Tc = 556 K and 557.3 K, respectively. The low saturation magnetisation, low optical absorption and highly crystalline structure of TbErIG (O2 and Ar) films mean that these films may potentially be used in a magneto-optical compact isolator in the visible and NIR regions.
关键词： nanostructures,Sol-gel,magnetic properties,X-ray diffraction,optical properties
更新于2025-09-10 09:29:36
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Structural, Optical and Magnetic Properties of Ultramarine Pigments: A DFT Insight
摘要： The ultramarine pigments are among the most widely used coloring materials since the antiquity till present times. Despite many experimental studies, the characterization of ultramarines is still incomplete. In this work we reported for the first time the density functional theory results obtained for realistic periodic and large cluster models of ultramarines with blue S3- and yellow S2- chromophores. Periodic calculations provided insight into Sn- siting inside aluminosilicate cages, normally not resolved well in experimental structural data. All electron calculations performed on large cluster models showed that the optical properties of S3- ions depend little on their orientation within cavities, unless strong distortion from free S3- ion C2v symmetry is enforced by the lattice. No magnetic coupling between S3- species occupying adjacent cages was found. Upon the present results observed differences in the averaging of electron resonance signals should be rather ascribed to different S3- dynamical effects. Though the quantitative computational treatment of S2- systems is more challenging, due to near orbital degeneracy, the qualitative results show that the electronic structure and spectroscopic properties of embedded S2- radicals are more sensitive to the environment than in the case of S3- species.
关键词： S3- chromophores,density functional theory,S2- chromophores,magnetic properties,aluminosilicate cages,ultramarine pigments,optical properties
更新于2025-09-10 09:29:36
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The new ordered double perovskite SrLaCuIrO6
摘要： The new fully rock-salt ordered Ir5+ double perovskite SrLaCuIrO6 was synthesized, and its structural, magnetic and electronic properties were investigated. The compound crystallizes tetragonally (space group I4/m). The Cu2+ cation leads to strong Jahn-Teller distortion of the CuO6 octahedra. The compound shows semiconducting behavior with an estimated band gap of approximately 0.2 eV. At around 10 K a magnetic transition is observed.
关键词： D. Magnetic properties,E. High-temperature synthesis,A. Double perovskite,D. Jahn-Teller distortion
更新于2025-09-10 09:29:36