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Thiacalix[4]arene-Supported Tetranuclear Tb <sup>III</sup> and Eu <sup>III</sup> Compounds: Synthesis, Structure, Luminescence, and Magnetism
摘要： Two tetranuclear compounds [Ln4Na(μ4-OH)(TC4A)2(acac)4] [Ln = Tb (1), Eu (2)] (acac = acetylacetonate) were synthesized and characterized based on p-tert-butylthiacalix[4]arene (H4TC4A). Compounds 1 and 2 are isostructural and crystallize in the monoclinic C2/c space group. There are two crystallographically independent metal atoms in one asymmetric unit. Ln1, Ln2, and two metal atoms generated by the symmetry operation are bridged by one μ4-OH group to form a planar tetragonal Ln4(μ4-OH) unit. Each Ln4(μ4-OH) unit is surrounded by four acac anions and two disordered sodium ions in the planar direction. The upper and lower positions of the Ln4(μ4-OH) unit are further coordinated by two cone-shaped TC4A ligands to form a sandwich-type molecular structure. Luminescent measurements reveal that both compounds 1 and 2 exhibit good photoluminescent properties. Moreover, the static and dynamic magnetic properties of compound 1 were also investigated, which demonstrates that 1 is one functional material candidate combining luminescent and antiferromagnetic properties in one molecule.
关键词： Thiacalix[4]arene,Lanthanides,Cluster compounds,Magnetic properties / Luminescence,Coordination chemistry
更新于2025-09-19 17:15:36
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Photoinduced effects on the magnetic properties of the (Fe <sub/>0.2</sub> Cr <sub/>0.8</sub> ) <sub/>1.5</sub> [Cr(CN) <sub/>6</sub> ] Prussian blue analogue.
摘要： One of the most attractive characteristics of some Prussian blue derivatives is the sensitivity of their magnetic properties to the irradiation with light. In this work photoinduced effects in the (Fe0.2Cr0.8)1.5 [Cr(CN)6]·15 H2O PBA have been studied by means of X ray-based spectroscopies and magnetometry. It is found that the photosensitivity of this compound is mostly centred on the Fe cations: the exposure to green light induces a transfer of electrons from them to the Cr that provokes a reversal of the previously existing linkage isomerization and increases the elastic strain caused by the mis?t of the unit cells of the Fe–NC–Cr and Cr–NC–Cr sublattices. The green light also quenches the magnetism of the FeII high-spin (HS) ions present in the sample and reduces the magnetic moments of most of the Cr cations except for CrII HS. Our study highlights the important role played by the mismatch between the unit cells of the coexisting sub-lattices in ternary Prussian blue analogues.
关键词： magnetometry,photoinduced effects,magnetic properties,elastic strain,X-ray spectroscopies,Prussian blue analogues,linkage isomerization
更新于2025-09-19 17:15:36
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Effect of Zr Doping on the Magnetic and Phase Transition Properties of VO2 Powder
摘要： In this work, V1?xZrxO2 powder (x = 0, 0.01, 0.02, 0.04) was synthesized by two step hydrothermal method. The micro-topography, magnetic and phase transition properties have been investigated using various measurement techniques. All prepared V1?xZrxO2 powder samples exhibit monoclinic structure at room temperature. With the Zr4+ ions doping concentration increased, the shapes of VO2 particles change from spherical to rectangular slice. Besides, the saturation magnetic moment of the samples decrease with the increase of doped Zr4+ ions concentration, while their phase transition temperature increase gradually with Zr ions doping at a rate of around 2 ?C/at% on average. We investigated the Zr doping effects on V-V dimers and con?rmed the role of V-V dimers in phase transition. We speculate that more V-V dimers form with Zr doping by magnetic measurements, which result in the monoclinic phase of Zr-doped VO2 sample is more stable than rutile phase. Therefore the phase transition temperature is elevated by Zr doping in our experiment. We further consider that the VO2 phase transition should be ascribed to Peierls transition caused by the changing of V-V dimers.
关键词： V-V dimer,magnetic properties,Zr-doped,phase transition temperature
更新于2025-09-19 17:15:36
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Intrinsic defects in and electronic properties of <i>θ</i> -Al <sub/>13</sub> Fe <sub/>4</sub> : an <i>ab initio</i> DFT study
摘要： θ-Al13Fe4 exhibits a rich variety of crystal physics. It contains twenty crystallographically different atomic species with a diversity of chemical coordination. An understanding of its structural and physical properties is a prerequisite for controlling its formation and its use. Here we investigate systematically the intrinsic defects in θ-Al13Fe4 using a ?rst-principles density-functional theory method. The calculations reveal that among the various intrinsic defects it is energetically favourable for Fe substitution of Al but on just three of the ?fteen Al sites. This results in a new structural model, Al68Fe24(Al, Fe)4(Al, Fe)2(Al, Fe)4 (the Roman numerals represent the Al sites) which updates the thermodynamic model, currently in use, which is associated with the formation of vacancies on some of the Al sites. The calculations demonstrate that the addition of Fe induces magnetism which gives rise to clustering. The calculations provide the dependence of the lattice parameters on Fe concentration and explain the experimental data in the literature. The information obtained here provides insight into the formation and properties of θ-Al13Fe4 and its role in the solidi?cation of Al alloys, in determination of the microstructure and related mechanical properties of the products, and in catalysis for organic reactions.
关键词： magnetic properties,density-functional theory calculations,intrinsic defects,θ-Al13Fe4,phase stability
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE 13th Nanotechnology Materials and Devices Conference (NMDC) - Portland, OR, USA (2018.10.14-2018.10.17)] 2018 IEEE 13th Nanotechnology Materials and Devices Conference (NMDC) - Magnetic Characterization of Cobalt Selenide and Nickel Selenide Thin Films
摘要： Transition metal dichalcogenides (TMDCs) are a family of materials whose crystalline structure consists of a layer of transition metal atoms sandwiched between 2 layers of chalcogenide atoms. Some of these materials can be grown in 2D hexagonal phase and show tunability of their electrical and magnetic properties based on layer thickness. One aspect of these materials that has received little attention is their magnetic properties. Hence, we have investigated magnetic properties of CoSe and NiSe their heterostructure. The reason for choosing these intrinsically ferromagnetic transition metal atoms based TMCs was to examine how reduction from the bulk to 2D films would influence the magnetic activity of these samples. In order to produce large area films, we have employed atomic layer deposition (ALD) for growth of uniform, few layer-thick films. First the composition and crystal structure of these films are characterized, and then their magnetic properties analyzed. We have found that thin films of both these materials show mostly paramagnetic behavior.
关键词： cobalt selenide,magnetic properties,Transition metal chalcogenides,thin film,nickel selenide
更新于2025-09-19 17:15:36
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Patterned arrays of assembled nanoparticles prepared by interfacial assembly and femtosecond laser fabrication
摘要： Creating shape-defined structures of inorganic nanoparticles in a maskless and template-free fashion would advance the engineering of nanoparticle-based devices and structures with desired configurations for various applications. In this work, a novel fabrication protocol combining bottom-up interfacial assembly and subtractive laser patterning was developed for creating patterned arrays of assembled nanoparticles. A solid film of magnetic nanoparticles (10 nm, monodisperse CoFe2O4) was assembled as a nanoparticle film (thickness less than 100 nm) on liquid interface under guiding field, and it was further transferred to Si substrate followed by selective material removal using femtosecond laser pulses, producing patterned arrays (typical size of 3 μm) of assembled nanoparticles. The size, shape, and arrangement of the patterned arrays were finely regulated by adjusting the laser pulse energy and laser scanning path. The magnetization behavior and magnetic anisotropy of the patterned arrays differ from those of the nanoparticle-assembled film, as reflected by the changes of coercivity and squareness along the out-of-plane direction. The presented fabrication protocol is compatible with microelectronic fabrication techniques and can be applied to various inorganic nanoparticles.
关键词： Magnetic properties,Femtosecond laser fabrication,Interfacial assembly,Nanoparticle patterning,Collective properties
更新于2025-09-19 17:13:59
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Room temperature ferromagnetism in ball milled Cu-doped ZnO nanocrystallines: an experimental and first-principles DFT studies
摘要： Experimental and theoretical studies on the room temperature ferromagnetism of ball milled Zn0.95Cu0.05O nanocrystalline, were reported. X-ray diffraction analysis reveals that the most dominant crystalline phase is hexagonal wurtzite with presence of weak peaks due to Cu and CuO. Rietveld analysis indicated that the crystallite size decreases with increasing milling time, while the strain enhanced with milling time. Magnetic measurements using SQUID expose remarkable room temperature ferromagnetic ordering for milled samples. The physical origin of the ferromagnetism order has been explained using a bound magnetic polaron model. Theoretical calculations based on First principles methods were employed to calculate the electronic structures and magnetic properties of Cu doping and zinc and oxygen vacancies behavior of Zn1?xCuxO. It was found that a Cu dopant leads to induce magnetism and exhibits an increasing of magnetic moment when Zn vacancy are introduced.
关键词： Room temperature ferromagnetism,Ball milled Cu-doped ZnO,Magnetic properties,Nanocrystalline,First-principles DFT
更新于2025-09-19 17:13:59
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Electro-absorption spectra of magnetic states of diamond shaped graphene quantum dots
摘要： In this work, employing restricted Hartree-Fock (RHF) as well as unrestricted Hartree-Fock (UHF) mean-field theory and incorporating long-range coulomb interactions within the Pariser-Parr-Pople (PPP) model based Hamiltonian, the effect of size and electric field on the optical properties of various magnetic states of diamond shaped graphene quantum dots (DQDs) has been elucidated. Our calculations have demonstrated that the energetic ordering of excited states and consequently the sequence of electric-field induced phase transition exhibited by the different magnetic phases changes with varying size of DQDs. The optical band-gap for the AF state decreases very gradually as compared to that of the FM and NM configurations, with increase in size of DQD. It is observed that the optical spectrum of the anti-ferromagnetic (AF) state exhibits a spin-sensitive splitting, while no such splitting is observed for the ferromagnetic (FM) configuration, under the application of electric field. In addition, our computations have established that the magnitude of optical band-gap splitting and the shifting trends (red-shift or blue-shift) of the optical spectrum of spin-up orbitals with respect to that of spin-down orbitals of the AF phase, with the application of electric field, can be tuned by changing the size of DQD.
关键词： Electro-absorption spectra,Phase transition,Pariser-Parr-Pople model,Graphene quantum dots,Magnetic properties
更新于2025-09-19 17:13:59
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Structure, electrical and magnetic properties of Co <sub/>0.8</sub> Zn <sub/>0.2</sub> Fe <sub/>2</sub> O <sub/>4</sub> /(K <sub/>0.47</sub> Na <sub/>0.47</sub> Li <sub/>0.6</sub> ) NbO <sub/>3</sub> bilayered thin films grown by pulsed laser deposition
摘要： Structural, ferroelectric, and magnetic properties of lead-free bilayer composite films with composition (K, Na, Li) NbO3-CoZnFe2O4 (P-S) and CoZnFe2O4-(K, Na, Li) NbO3 (S-P) layers deposited on Pt/Si substrates by a pulsed laser deposition technique have been studied. Structural analysis carried out by X-ray diffraction and Raman scattering confirmed the formation of individual phases of perovskite and spinel without any intermediate/secondary phase. To probe the stoichiometric elemental composition and cationic distribution at the interstitial sites, X-ray photoelectron spectroscopy measurement was carried out, which confirmed the mixed state of Fe-ions valence, while the Zn2+ state was retained. Ferroelectric and ferromagnetic behavior of the bilayered films was observed concurrently depending upon the growth sequence adopted. Magnetic properties of the film with spinel on the top layer exhibited higher saturation magnetization. Dielectric permittivity follows the Maxwell–Wagner polarization caused by thermally agitated carriers. Appreciable ferroelectric properties were achieved in S-P films while the P-S film exhibited a lossy ferroelectric hysteresis loop, which is attributed to a high leakage current value.
关键词： pulsed laser deposition,structural properties,magnetic properties,electrical properties,bilayered thin films
更新于2025-09-16 10:30:52
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Effect of confinement potential shape on the electronic, thermodynamic, magnetic and transport properties of a GaAs quantum dot at finite temperature
摘要： The effect of the shape of the confinement potential on the electronic, thermodynamic, magnetic and transport properties of a GaAs quantum dot is studied using the power-exponential potential model with steepness parameter p. The average energy, heat capacity, magnetic susceptibility and persistent current are calculated using the canonical ensemble approach at low temperature. It is shown that for soft confinement, the average energy depends strongly on p while it is almost independent of p for hard confinement. The heat capacity is found to be independent of the shape and depth of the confinement potential at low temperatures and for the magnetic field considered. It is shown that the system undergoes a paramagnetic-diamagnetic transition at a critical value of the magnetic field. It is furthermore shown that for low values of the potential depth, the system is always diamagnetic irrespective of the shape of the potential if the magnetic field exceeds a certain value. For a range of the magnetic field, there exists a window of p values in which a re-entrant behavior into the diamagnetic phase can occur. Finally, it is shown that the persistent current in the present quantum dot is diamagnetic in nature and its magnitude increases with the depth of the dot potential but is independent of p for the parameters considered.
关键词： transport properties,thermodynamic properties,canonical ensemble approach,electronic properties,quantum dot,GaAs,paramagnetic-diamagnetic transition,persistent current,magnetic properties,power-exponential potential model,confinement potential
更新于2025-09-11 14:15:04