A manifestation of magnetism of bismuth in iron garnet films

Bismuth iron garnet films prepared through electron-beam and laser-induced evaporation on (001)-oriented substrates of scandium gallium gadolinium garnet are investigated using ferromagnetic resonance. It is assumed that the additional minima observed in the angular dependence of the resonance field can be associated with the magnetic moment of bismuth ions.     

Synthesis and Molecular Structure of 3-[N-Acetyl(3,5-dimethylphenyl)amino]-5,7-di(tert-butyl)-2-{5,8-dimethyl-4-[(3,5-dimethylphenyl)amino]quinolin-2-yl}tropone

Russian Journal of General Chemistry - Acylation of 5,7-di(tert-butyl)-2-{5,8-dimethyl-4-[(3,5-dimethylphenyl)amino]quinolin-2-yl}-3-[(3,5-dimethylphenyl)amino]tropone leads to...     

The first representative of a new class of charge transfer complexes in o-quinone series for organic semiconductors

The first representative of a new class of charge transfer complexes for organic semiconductors was synthesized. The reaction of p-nitroaniline (PNA) with [1,10]-phenanthroline-5,6-dione (PD) results in the formation of a stable molecular charge transfer (CT) complex PNA₃-PD₂ in a ratio of 3:2. The structure of the molecular CT complex PNA₃-PD₂ was established by X-ray diffraction studies. Using the density functional theory method, it is shown that several types of intermolecular interactions are realized in the complex: between the PNA amino group and the nitro group of another PNA molecule, carbonyl groups, and PD nitrogen atoms. Complex PNA₃-PD₂ is stable only in solid form. The diffuse reflectance UV–vis spectrum of PNA₃-PD₂ crystal powder is characterized by the intense weakly structured long-wavelength absorption band up to 650 nm. Quantum chemical calculations of the electronic structure have shown that the complex PNA₃-PD₂ is a straight-band semiconductor with a band gap of 2.11 eV.     

High-frequency susceptibility and ferromagnetic resonance in multidomain thin films of the yttrium-iron garnet type

The field dependence of the high-frequency susceptibility and the ferromagnetic resonance were experimentally studied in a thin (d≈0.1 µm) (111)-oriented single-crystal film of substituted yttrium-iron garnet with the factor q?1. It was shown that the anomaly in the high-frequency susceptibility observed in a magnetic field H parallel to the normal to the film surface in the magnetization saturation region (H≈H_s) has a dual nature; more specifically, this anomaly is associated with an abrupt collapse of the stripe domain structure and a ferromagnetic resonance in the experimental configuration H ∥ [111] and h ⊥ H. In this case, the film transition from the inhomogeneous multidomain state to the homogeneous (single-domain) state at the point H≈H_s has no indications of a second-order phase transition. The experimental frequency-field dependence of ferromagnetic resonance (FMR) in the sample under study, having a characteristic minimum at the point ω₀=5 MHz and H_FMR=H_s, agrees qualitatively and quantitatively with calculations. The influence of the cubic magnetic anisotropy and the film thickness on the FMR spectrum and the orientation of the spontaneous magnetization in domains with respect to the film plane in the zero field H was theoretically studied.     

Comparison of different methods of measurement of pressure of underwater shock waves generated by electrical discharge

Different methods for measurement of strong underwater shock waves pressure pulses with peak pressures of up to 200 MPa and rise time of tens to hundreds of nanoseconds are described and compared. The experimental techniques include direct methods of pressure measurement using various electromechanical gauges such as quartz, carbon-based, and commercially available PCB gauges, and nondirect methods based on measurement of the velocity of the shock wave such as time-of-flight and fast-streak photography. Advantages and disadvantages of the used gauges and methods are discussed. The shock waves were produced by underwater electrical discharge (discharge current amplitude ≤100 kA, pulse duration ≤5 μs) initiated by an exploding wire. A good correspondence between the pressure amplitudes measured by the various gauges and methods was observed. The obtained dependence of the shock wave pressure on the distance from the discharge channel was found to be best fitted by a r ^−0.7 law. It is also shown that none of these methods can be used to determine the time evolution of the pressure behind the front of the shock wave.     

Structure and properties of deposited yttrium iron garnet films

Ferromagnetic resonance (FMR) and vibrating-sample magnetometer techniques were used to study the nature of the structural characteristics of yttrium iron garnet films deposited through either liquid phase epitaxy or laser evaporation on a (111)-oriented gallium gadolinium garnet substrate. It was proved that, based on the experimentally observed cubic magnetic anisotropy, deposited films should be considered to be single crystals. However, the absence of the FMR domain branch in a nonsaturated film and the shape of the magnetization curve indicate that a deposited film when demagnetized does not have a domain structure, as would be expected for a single-crystal film. According to the model proposed, a deposited film consists of close-packed single-crystal fragments with equal crystallographic orientation, the boundaries between which are in a partially atomically disordered state. As a result, such a film is both locally and macroscopically anisotropic, like a continuous single crystal. This film can split into domains only within a fragment (as is the case in a magnetic granular polycrystal); however, this does not happen, because the linear dimensions of a submicroscopic fragment are smaller than the equilibrium domain width.     

Synthesis and molecular structure of 7<Emphasis Type="Italic">H</Emphasis>-12-oxa-3,7-diazapleiadene-substituted 1,3-tropolones

An acid-catalyzed reaction of substituted 2-methyl-7H-12-oxa-3,7-diazapleiadenes with 1,2-benzoquinones leads to 7H-12-oxa-3,7-diazapleiadene-substituted 1,3-tropolones. Molecular structure of 5,7-di(tert-butyl)-2-[9,11-di(tert-butyl)-4-methyl-7H-12-oxa-3,7-diazapleiaden-2-yl]-4-nitro-1,3-tropolone was established by X-ray crystallography. Energy and structural characteristics of isomeric 5,7-di(tert-butyl)-2-[9,11-di(tert-butyl)-4-methyl-7H-12-oxa-3,7-diazapleiaden-2-yl]-4-nitro-1,3-tropolones in the gaseous phase and a polar solution were studied by the PBE0/6-31G** method.     

Synthesis and Structure of New 2-(2-Quinolyl)-1,3-tropolone Derivatives

4,6-Di-tert-butyl-3-nitro-1,2-benzoquinone reacts with substituted 2-methylquinolines to give the corresponding 2-(2-quinolyl)-4-nitro-1,3-tropolones and 2-(2-quinolyl)-1,3-tropolones.