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Spin-Glass Behavior, Magnetic, and IR Spectroscopy Analysis of Multimetallic Compound Ni <sub/><b>0.25</b> </sub> Mn <sub/><b>1.25</b> </sub> [Fe(CN) <sub/><b>6</b> </sub> ]·6.1H <sub/><b>2</b> </sub> O
摘要： Multimetallic Prussian blue compound Ni0.25Mn1.25[Fe(CN)6]?6.1H2O has been prepared by coprecipitation. The temperature-dependent magnetic susceptibilities show the magnet transition for the compound at 8.5 K. According to DC variable-temperature magnetic susceptibility paramagnetic Curie temperature ?? is ?9.32 K. The observed value of coercive field (Hc) and the remanent magnetization (Mr) for the compound are 0.32 KOe and 0.36??B. According to study of zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves and AC magnetization curves, there exists a spin-glass behaviour in the compound, which exhibits freezing temperature ????=7.76 K, below magnetic transition ????=8.5 K; that glass behavior is termed “reentrant” spin glass.
关键词： magnetic properties,Prussian blue,spin-glass,multimetallic compound
更新于2025-09-09 09:28:46
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A novel approach to prepare one-pot Fe/PPy nanocomposite and evaluation of its microwave, magnetic, and optical performance
摘要： The aim of this study was preparation of Fe/Fe2O3/Fe3O4 (Fe)/polypyrrole (PPy) nanocomposite using reductive method and investigation of its microwave absorbing properties using polymethylmethacrylate (PMMA) medium. Firstly, PPy was prepared by an oxidative polymerization method with Fe3+ as a doping agent. Next, the Fe/PPy nanocomposite was formed by insitu reduction of Fe2+ and remained Fe3+ with sodium borohydride solution under an inert nitrogen atmosphere. Finally, PPy and Fe/PPy nanostructures were separately suspended within the PMMA matrix to examine their microwave absorbing characteristics. The prepared PPy and Fe/PPy nanostructures were studied using the Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The diffuse reflection spectroscopy (DRS) analysis presented a 1.79 eV band gap for the Fe/PPy nanocomposite based on the Kubelka–Munk theory. The vibrating sample magnetometer (VSM) revealed that magnetic properties were reinforced in the Fe/PPy nanocomposite. According to the results obtained by vector network analyzer (VNA), the maximum reflection loss of Fe/PPy/PMMA nanocomposite was -76.02 dB at 8.96 GHz with a thickness of 3.2 mm, absorbing all of the x-band frequency more than 12.72 dB with a thickness of 2.8 mm. Interestingly, the Fe/PPy/PMMA nanocomposite demonstrated a bandwidth > 3.4 GHz more than 10 dB from 2.2 to 3.2 mm at the x-band frequency.
关键词： Optical performance,Magnetic properties,Fe/PPy/PMMA,Microwave absorption
更新于2025-09-09 09:28:46
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Influencing Optical and Magnetic Properties of NiCr2O4 by the Incorporation of Fe(III) for Cr(III) Following Epoxide Gel Synthesis
摘要： With the objective of modifying the optical and magnetic properties of the spinel NiCr2O4, incorporation of 50 mol.% of Fe3+ for Cr3+ has been attempted following an epoxide-mediated gel synthesis. From the Le Bail re?nement of powder x-ray diffraction patterns of xerogels after calcination at 1000°C for 2 h in Fd-3 m space group, the lattice parameter of resultant spinels showed a marginal increase from 8.3117 (21) for NiCr2O4 to 8.3177 (26) A? for NiCrFeO4. The square morphology of the crystallites was observed in scanning electron microscopic images, and the energy-dispersive spectroscopy results con?rmed the uniform presence of Ni, Cr and Fe in these samples. Lattice fringes in high-resolution transmission electron microscopic images could be related to the cubic spinel structure. The optical band gap was found to decrease from 1.68 for NiCr2O4 to 1.41 eV for NiCrFeO4. Substitution of iron for chromium was found to reduce its catalytic ef?ciency for photo-degradation of aqueous rhodamine-6G (Rh-6G) dye solution under UV–visible radiation.
关键词： x-ray methods,Spinels,magnetic properties,calcination,sol–gel processes
更新于2025-09-09 09:28:46
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Mn doped BiNbO4 ceramics: Thermal stability, phase transitions, magnetic properties, NEXAFS and ESR spectroscopy
摘要： Thermal stability, magnetic properties, ESR (Electron Spin Resonance) and NEXAFS (Near-Edge X-ray Absorption Fine Structure) spectra of the orthorhombic and triclinic modi?cations of solid solutions BiNb1-xMnxO4-d have been studied. X-ray diffraction determined the reversibility of the phase transition from the high-temperature triclinic modi?cation to the orthorhombic modi?cation at 950 (cid:1)C in the BiNb1-xMnxO4-d solid solutions. The ESR spectra of the triclinic BiNb1-xMnxO4-d revealed the sextet structure of Mn(II) ions with 8.4 mT splitting and some features at g ? 3.80 and 1.47, and a broad diffuse band with g ~ 2.2 having a sextet with 8e9 mT splitting and g ? 2.0 against its background. The measurements of magnetic susceptibility allowed us to calculate the parameters of exchange interactions in dimers and the distribution of manganese atoms (II), (III) and (IV) in dependence on concentrations of the solid solutions in the orthorhombic and triclinic modi?cations. It was established that in the manganese-doped solid solutions of triclinic modi?cation, the degree of aggregation and the nuclearity of the clusters were higher than in the solid solutions of orthorhombic modi?cation. The clusters were presented in the forms of dimers and trimers of Mn(II), Mn(III) and Mn(IV) atoms with different valence atoms with antiferro- and ferromagnetic types of exchange. The solid solutions BiNb1-xMnxO4-d as well as manganese oxides MnO, Mn2O3 and MnO2 were studied by the NEXAFS spectroscopy in order to determine the degrees of oxidation of manganese atoms. The DSC (Differential Scanning Calorimetry) curves of the samples BiNb1-xMnxO4-d revealed the endothermic effects associated with the phase transition from the orthorhombic modi?cation to the triclinic one at 1050 (cid:1)C (x ? 0.03) and 1048 (cid:1)C (x ? 0.06). The melting peaks were observed at 1231 (cid:1)C (x ? 0.03) and 1220 (cid:1)C (x ? 0.06), respectively. The differences in the magnetic characteristics and in the results of ESR and NEXAFs spectroscopy of the BiNb1-xMnxO4-d of orthorhombic and triclinic modi?cations were due to the relative content of Mn(II), Mn(III), Mn(IV) ions and the degree of distortion of their local surroundings, composition and nature of exchange interactions in the clusters of manganese atoms.
关键词： ESR,Phase transitions,NEXAFS,Thermal stability,Magnetic properties
更新于2025-09-09 09:28:46
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Electrolyte-based ionic control of functional oxides
摘要： The use of electrolyte gating to electrically control electronic, magnetic and optical properties of materials has seen strong recent growth, driven by the potential of the many devices and applications that such control may enable. Contrary to initial expectations of a purely electrostatic response based on electron or hole doping, electrochemical mechanisms based on the motion of ions are now understood to be common, suggesting promising new electrical control concepts.
关键词： optical properties,electrochemical mechanisms,electrostatic response,electronic properties,electrolyte gating,magnetic properties
更新于2025-09-04 15:30:14
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Magnetism of Eu-doped GaN modulations by spinodal nanodecomposition
摘要： By the Monte Carlo method, magnetic properties have been investigated for Eu-doped GaN involving internal nanostructures induced by nanoscale spinodal decomposition, where these nanostructures are spontaneously or artificially formed. In the present simulations, hysteretic and nonhysteretic magnetization curves are observed in the systems with the large-sized and small-sized nanostructures, respectively. These nanostructures affect the blocking temperatures as well. Furthermore, they influence temperature-dependent energy barriers of spin flipping; therefore, the simulations suggest that the magnetization is thermally stable. However, we observe that the blocking temperatures are smaller than the experimental values, which may be due to atomic vacancies.
关键词： magnetic properties,blocking temperatures,Eu-doped GaN,Monte Carlo method,spinodal decomposition
更新于2025-09-04 15:30:14
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Ab-initio study on electronic and magnetic properties of (Ga,Co) co-doped ZnO
摘要： Using first-principles calculations based on density functional theory within GGA formalism, we have studied the electronic structure and magnetic properties of (Ga,Co) co-doped ZnO system. The effect of impurity distances on ferromagnetic and antiferromagnetic ground state in Co0.056Zn0.944O has been studied. For the closest Co-Co distance, a ferromagnetic ground state with total magnetic moment of ~3.00μμ’ per Co atom has been found. The electronic structure also displays a nearly halfmetallic order. Conversely, for the farthest Co-Co distance an antiferromagnetic ground state was found for Co0.056Zn0.944O. When Zn2+ ions are replaced by Ga ions in Co0.056Zn0.944O, the new (Ga,Co) co-doped ZnO system is more energetically stable. It has also been found that Ga-doping reduces the Co0.056Zn0.944O band gap due to the sp-d exchange interactions, which is in good agreement with the experimental data. Moreover, the Ga-doping changes the nearly halmetallic order of Co0.056Zn0.944O to metallic. Results also show that Ga0.029Co0.056Zn0.915O is still ferromagnetic with a total magnetic moment of ~3.00μμ’ per Co atom. It was also found that the ferromagnetic ground state in (Ga,Co) co-doped ZnO vanishes as Ga concentration increases.
关键词： GGA formalism,(Ga,ab-initio,density functional theory,electronic structure,Co) co-doped ZnO,magnetic properties
更新于2025-09-04 15:30:14
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Integration of sputter-deposited multiferroic CoFe2O4-BiFeO3 nanocomposites on conductive La0.7Sr0.3MnO3 electrodes
摘要： The structure, magnetic and ferroelectric properties of sputtered epitaxial CoFe2O4-BiFeO3 (CFO-BFO) nanocomposite thin films grown on La0.7Sr0.3MnO3 (LSMO) layers on (001) oriented SrTiO3 (STO) substrates and on STO-buffered Si are described. The as-grown LSMO thin films were smooth and poorly conductive but the resistivity was reduced and the surfaces roughened after annealing. Cosputtered CFO and BFO on STO formed vertically aligned nanostructures consisting of epitaxial spinel CFO pillars within a perovskite BFO matrix, but the rough surface of the annealed LSMO film promoted additional CFO pillar orientations. A reorientation of the CFO magnetic easy axis to an in-plane direction occurred as the LSMO became thicker due to changes in the strain state of the CFO pillars. The LSMO underlayer enabled the ferroelectric response of the BFO to be measured. Nanocomposites were grown onto LSMO/SrTiO3/Si which provides a path towards large scale integration of electrically contacted nanocomposites on Si.
关键词： La0.7Sr0.3MnO3,sputter-deposited,ferroelectric,magnetic properties,nanocomposites,CoFe2O4-BiFeO3,multiferroic
更新于2025-09-04 15:30:14
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摘要： The spin-orbit coupling (SOC) interactions, electron-correlation effects, and Hund coupling cooperate and compete with each other, leading to novel properties, quantum phase, and nontrivial topological electronic behavior in iridium oxides. Because of the well-separated IrO6 octahedra approaching cubic crystal-field limit, the hexagonal iridates Sr3MIrO6 (M = Sr, Na, and Li) serve as canonical model systems to investigate the underlying physical properties that arise from the novel jeff state. Based on density-functional theory calculations complemented by Green’s function methods, we systematically explore the critical role of SOC on the electronic structure and magnetic properties of Sr3MIrO6. The crystal-field splitting combined with correlation effects are insufficient to account for the insulating nature, but the SOC interaction is the intrinsic source to trigger the insulating ground states in these hexagonal iridates. The decreasing geometry connectivity of IrO6 octahedra gives rise to the increase of effective electronic correlations and SOC interactions, tuning the hexagonal iridates from low-spin jeff = 1/2 states with large local magnetic moments for the Ir4+ (5d 5) ions in Sr4IrO6 to nonmagnetic singlet Jeff = 0 states without magnetic moments for the Ir5+ (5d 4) ions in Sr3NaIrO6 and Sr3LiIrO6. The theoretical calculated results are in good agreement with available experimental data, and explain the magnetic properties of Sr3MIrO6 well.
关键词： electronic structure,insulating state,magnetic properties,iridates,spin-orbit coupling
更新于2025-09-04 15:30:14
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Magnetic Properties of Pure and Doped Gallium Nitride Nanocrystals
摘要： In the present paper, Ga1?xCoxN, Ga1?xNixN and Ga1?xTbxN (0 ≤ x ≤ 0.1) nanocrystals have been synthesized by a facile solvothermal method. Crystallographic characterization of synthesized materials has been done using powder X-ray diffraction technique. Recorded diffraction patterns reveal the formation of wurtzite (hexagonal) structured GaN nanocrystals. Electron microscopic studies have been carried for the detailed topographical and morphological analyses of synthesized nanomaterials. Recorded electron micrographs indicate the formation of nearly mono-disperse nanoparticles, having average size ～4 nm. Magnetic measurements of doped nanocrystals revealed ferromagnetic behavior at room temperature however pure GaN is diamagnetic at room temperature.
关键词： Crystallography,Doping,Gallium Nitride Nanocrystals,Magnetic Properties
更新于2025-09-04 15:30:14