Structural and Magnetic Properties of FeNi Films and FeNi-Based Trilayers with Out-of-Plane Magnetization Component

FeNi films of different thickness and FeNi/(Fe, Co)/FeNi trilayers were prepared by magnetron sputtering deposition onto glass substrates. The permalloy films had a columnar microstructure. The detailed analysis of the magnetic properties based on the magnetic and magneto-optical measurements showed that at thicknesses exceeding a certain critical thickness, hysteresis loops acquire a specific shape and the coercive force of the films increase sharply. The possibility of the estimation of the perpendicular magnetic anisotropy constant using the Murayama equation for the thickness dependence of saturation field was demonstrated. The results of studies of the structural and magnetic properties of FeNi films laminated by Fe and Co spacers with different thickness are presented.This research was funded by the Russian Science Foundation (RSF), project no. 22-29-00980, https://rscf.ru/en/project/22-29-00980/ and in part by the Research Groups of the UPV-EHU

The low-temperature germinating spores of the thermophilic Desulfofundulus contribute to an extremely high sulfate reduction in burning coal seams

Burning coal seams, characterized by massive carbon monoxide (CO) emissions, the presence of secondary sulfates, and high temperatures, represent suitable environments for thermophilic sulfate reduction. The diversity and activity of dissimilatory sulfate reducers in these environments remain unexplored. In this study, using metagenomic approaches, in situ activity measurements with a radioactive tracer, and cultivation we have shown that members of the genus Desulfofundulus are responsible for the extremely high sulfate reduction rate (SRR) in burning lignite seams in the Altai Mountains. The maximum SRR reached 564 ± 21.9 nmol S cm−3 day−1 at 60°C and was of the same order of magnitude for both thermophilic (60°C) and mesophilic (23°C) incubations. The 16S rRNA profiles and the search for dsr gene sequences in the metagenome revealed members of the genus Desulfofundulus as the main sulfate reducers. The thermophilic Desulfofundulus sp. strain Al36 isolated in pure culture, did not grow at temperatures below 50°C, but produced spores that germinated into metabolically active cells at 20 and 15°C. Vegetative cells germinating from spores produced up to 0.738 ± 0.026 mM H2S at 20°C and up to 0.629 ± 0.007 mM H2S at 15°C when CO was used as the sole electron donor. The Al36 strain maintains significant production of H2S from sulfate over a wide temperature range from 15°C to 65°C, which is important in variable temperature biotopes such as lignite burning seams. Burning coal seams producing CO are ubiquitous throughout the world, and biogenic H2S may represent an overlooked significant flux to the atmosphere. The thermophilic spore outgrowth and their metabolic activity at temperatures below the growth minimum may be important for other spore-forming bacteria of environmental, industrial and clinical importance

On Nature of the Induced Anisotropy in the Chemically Deposited Со‒Р Films

The induced magnetic anisotropy in the Со‒Рfilms prepared by chemical deposition from liquid solutions in a magnetic field has been investigated. The pronounced difference between the anisotropy values and relaxation times points out the existence of different physical mechanisms responsible for the occurrence of anisotropy of the Со‒Р films at low and high pH values. Possible mechanisms of the induced anisotropy in the Со‒Р films prepared at different pH values are discussed

The Role of Periodic Structures in Light Harvesting

The features of light propagation in plant leaves depend on the long-period ordering in chloroplasts and the spectral characteristics of pigments. This work demonstrates a method of determining the hidden ordered structure. Transmission spectra have been determined using transfer matrix method. A band gap was found in the visible spectral range. The effective refractive index and dispersion in the absorption spectrum area of chlorophyll were taken into account to show that the density of photon states increases, while the spectrum shifts towards the wavelength range of effective photosynthesis

On Nature of the Induced Anisotropy in the Chemically Deposited Со‒Р Films

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The induced magnetic anisotropy in the Со‒Р films prepared by chemical deposition from liquid solutions in a magnetic field has been investigated. The pronounced difference between the anisotropy values and relaxation times points out the existence of different physical mechanisms responsible for the occurrence of anisotropy of the Со‒Р films at low and high pH values. Possible mechanisms of the induced anisotropy in the Со‒Р films prepared at different pH values are discussed

Magnetic Properties of Nickel-Titanium Alloy during Martensitic Transformations under Plastic and Elastic Deformation

This paper focuses on the processes of the occurrence of magnetization during structure formation in samples of Ni51Ti49 alloy under deformation conditions. The possibility of the existence of a phase with an FCC (face-centered cubic) lattice in titanium nickelide has been demonstrated by electron microscopy and electron diffraction. It has been discovered that the interplanar distances of BCC110 (body-centered cubic), FCC111, and HCP002 (hexagonal close packed) in the alloy under study have similar values, which indicates the possibility of their mutual polymorphic transformation. Based on the modular self-organization, a scheme of martensitic transformations in titanium nickelide from the B2 structure (BCC lattice) to the B19’ structure (HCP lattice) through an intermediate phase with an FCC lattice is proposed. It is shown that lenticular crystals appear in the Ni51Ti49 alloy under tensile deformation until rupture, which is accompanied by the onset of ferromagnetism. The effect of magnetization in Ni51Ti49 samples when immersed in liquid nitrogen has been also discovered. In this case, the reason for the appearance and disappearance of magnetization can be associated with microdeformation processes caused by direct and reverse martensitic transitions that occur during cooling and heating of the samples

The Cyclic Stability of Superelasticity in Aged Ti_49.3Ni_50.7 Single Crystals with Oxide Surface

The cyclic stability of superelasticity in compression in [001]B2-oriented Ti49.3Ni50.7 single crystals is considered in this paper. The crystals were aged at 823 K for 1.0 h in air and helium. It has been experimentally shown that a two-layered surface thin film, consisting of a Ni-free oxide layer and a Ni-rich sublayer, appears after the oxidation at 823 K in air. The surface layers have a weak effect on the forward B2-R-B19’ martensitic transformation temperatures: TR temperature increases by 4 K; Ms and Mf temperatures decrease by 6 K. The oxide layer does not affect either the superelasticity response during fatigue tests or the temperatures of reverse B19’-B2 martensitic transformation. The cracking of the surface oxide layer during fatigue tests was not found in [001]B2-oriented single crystals aged in air. This is contributed by the relaxation of internal stresses. Such internal stresses are caused by both the formation of an oxide layer during aging and the matrix deformation at the stress-induced martensitic transformation. The main relaxation mechanisms of the internal stresses are the oriented growth of Ti3Ni4 precipitation near a thin surface film at aging in air, the formation of dislocations near the precipitation-matrix interface and a fine twinned B19’-martensite at fatigue tests

The Cyclic Stability of Superelasticity in Aged Ti49.3Ni50.7 Single Crystals with Oxide Surface

The cyclic stability of superelasticity in compression in [001]B2-oriented Ti49.3Ni50.7 single crystals is considered in this paper. The crystals were aged at 823 K for 1.0 h in air and helium. It has been experimentally shown that a two-layered surface thin film, consisting of a Ni-free oxide layer and a Ni-rich sublayer, appears after the oxidation at 823 K in air. The surface layers have a weak effect on the forward B2-R-B19’ martensitic transformation temperatures: TR temperature increases by 4 K; Ms and Mf temperatures decrease by 6 K. The oxide layer does not affect either the superelasticity response during fatigue tests or the temperatures of reverse B19’-B2 martensitic transformation. The cracking of the surface oxide layer during fatigue tests was not found in [001]B2-oriented single crystals aged in air. This is contributed by the relaxation of internal stresses. Such internal stresses are caused by both the formation of an oxide layer during aging and the matrix deformation at the stress-induced martensitic transformation. The main relaxation mechanisms of the internal stresses are the oriented growth of Ti3Ni4 precipitation near a thin surface film at aging in air, the formation of dislocations near the precipitation-matrix interface and a fine twinned B19’-martensite at fatigue tests

Effect of Cu on Performance of Self-Dispersing Ni-Catalyst in Production of Carbon Nanofibers from Ethylene

The development of effective catalysts for the pyrolysis of light hydrocarbons with the production of carbon nanomaterials represents a relevant direction. In the present work, the influence of copper addition on performance of a self-dispersed Ni-catalyst and structural features of the obtained carbon nanofibers (CNFs) was studied. The precursors of Ni and Ni-Cu catalysts were prepared by activation of metal powders in a planetary mill. During contact with the C2H4/H2 reaction mixture, a rapid disintegration of the catalysts with the formation of active particles catalyzing the growth of CNFs has occurred. The kinetics of CNF accumulation during ethylene decomposition on Ni- and Ni-Cu catalysts was studied. The effect of temperature on catalytic performance was explored and it was shown that introduction of copper promotes 1.5–2-fold increase in CNFs yield in the range of 525–600 °C; the maximum CNFs yield (100 g/gcat and above, for 30-min reaction) is reached on Ni-Cu-catalyst at 575–600 °C. A comparative analysis of the morphology and structure of CNF was carried out using electron microscopy methods. The growth mechanism of carbon filaments in the shape of “railway crossties” on large nickel crystals (d > 250 nm) was proposed. It was found that the addition of copper leads to a decrease in the bulk density of the carbon product from 40–60 to 25–30 g/L (at T = 550–600 °C). According to the low-temperature nitrogen adsorption data, specific surface area (SSA) of CNF samples (at T 2/g, regardless of the catalyst composition; at T = 600 °C the introduction of copper contributed to an increase in the specific surface of CNF by 100 m2/g

Magneto-optical properties of nanoparticle dispersions based on Fe3O4, obtained by pulse laser ablation in a liquid

The structure, optical and magneto-optical properties of colloidal solutions of iron oxide nanoparticles obtained by pulsed ablation in distilled water, both without additives and with various functional additives: gold-hydrochloric acid, silicon oxide, and polyvinylpyrrolidone, have been studied. It is shown that the main magnetic phase is magnetite Fe3O4. The size distribution of nanoparticles and the degree of their agglomeration depend on the additives. In the absence of the latter, a very wide of size distributions and strong agglomeration of particles are observed. The narrowest distribution curve with a maximum corresponding to 7 nm and an almost complete absence of agglomeration are observed for particles synthesized in the presence of polyvinylpyrrolidone. The shape of the spectral dependence of magnetic circular dichroism, which generally corresponds to the spectrum of magnetite, undergoes some modifications for various additives, which is associated with defects in the distribution of iron ions between different positions in the crystal