A modification of the method for calculating the distribution function of random fields of dipole -dipole interaction in dilute magnetics using the expansion in the Gram-Charlier series with the help of Bell polynomials has been carried out. On the basis of this method, a model has been developed that allows us to estimate the ensemble magnetisation, the volume fractions of particles in different magnetic states, the volume concentration of the ferrimagnetic and its effective spontaneous magnetisations on the basis of experimental data on hysteresis characteristics. The proposed approach allows us to take into account the particle size distribution and magnetic states. The model has several advantages, such as the possibility of taking into account the cluster distribution of particles and applicability to the limiting cases of thin layer and thin filament. Examples of partial verification of this model on objects of artificial and natural origin are given.

The composition and magnetic properties of foraminifers from bottom sediments of the Mid-Atlantic Ridge and their artificial analogs obtained by hydrothermal synthesis were studied. The presence of magnetic hysteresis and theoretical modeling of hysteresis characteristics made it possible to assume the presence of grains of nonstoichiometric magnetite in single- and few-domain states.

The mineral composition, petrographic structure, and magnetic properties of artificial glasses obtained from high-temperature melting of mixtures of rocks of various geneses (volcanic–sedimentary rocks, quartzite–shales, and psammite–silt–pelite complexes) are studied. When glasses were synthesized, cooling and glass transition conditions of various durations were used. The formation of ferrimagnetic minerals is due to the composition of the stock and the cooling rate of the melt. The resulting magnetic particles during “fast” cooling are mainly in the superparamagnetic state (up to 90

The structural-phase, chemical composition and magnetic properties of artificial glasses obtained by high-temperature melting of rock mixtures of different genesis: volcanogenic-sedimentary rocks, quartzitic shales, psamite-silt-pelitic complexes were studied. Different in duration cooling and glass transition conditions were used for glass synthesis. The magnetic state of the iron-containing phase and the analysis of the presence and contribution of iron oxides to the magnetic properties were assumed to be the characteristic criterion determining the parameters of the glass formation process. It was shown that the total iron content in artificial glasses depends exclusively on the composition of the initial charge. In this case, the iron-containing component is mainly determined by sedimentary rocks. The formation of magnetic minerals is determined both by the composition of the charge and by the rate of cooling of the melt. During “fast” cooling, the formed magnetic particles are mostly (up to 90% or more of the total content of the magnetic phase in the sample) in a superparamagnetic state. During “slow” cooling, a mixture of particles of different sizes and, accordingly, in different magnetic states is formed: from superparamagnetic to low-domagnetic. The ferrimagnetic phase crystallizing in artificial glasses is represented by chemically heterogeneous aggregates of iron oxides, mainly non-stoichiometric magnetite.

The magnetic properties of Fe3O4–Fe3 – xTixO4 composites synthesized by various methods were simulated based on the model of an ensemble of magnetostatically interacting particles. The results are in good agreement with the hysteresis characteristics of the samples calculated earlier in the framework of the model of chemically heterogeneous two-phase particles. It is shown that the used approach is also applicable to the samples consisting mainly of superparamagnetic particles in which the saturation remanent magneti-zation is provided by the particles blocked due to the magnetostatic interaction.

—The magnetic properties of Fe 3 O 4 –Fe 3 – x Ti x O 4 composites synthesized by various methods were simulated based on the model of an ensemble of magnetostatically interacting particles. The results are in good agreement with the hysteresis characteristics of the samples calculated earlier in the framework of the model of chemically heterogeneous two-phase particles. It is shown that the used approach is also applicable to the samples consisting mainly of superparamagnetic particles in which the saturation remanent magnetization is provided by the particles blocked due to the magnetostatic interaction.

Abstract—The magnetic properties of Fe3O4–Fe3 – xTixO4 composites synthesized by various methods were simulated based on the model of an ensemble of magnetostatically interacting particles. The results are in good agreement with the hysteresis characteristics of the samples calculated earlier in the framework of the model of chemically heterogeneous two-phase particles. It is shown that the used approach is also applicable to the samples consisting mainly of superparamagnetic particles in which the saturation remanent magnetization is provided by the particles blocked due to the magnetostatic interaction.

A collection of irghizites and microirghizites selected by the authors during two field seasons 2018–2019 at the Zhamanshin impact structure (Kazakhstan) was studied. The main task is to identify and study mineral inclusions regarding the morphological features of the samples. This study will help to resolve existing ambiguities and contradictions in the data on these impact rocks. On the other hand, it will serve to understand the genesis and ontogenesis of the impact glasses (i.e., zhamanshinites, irghizites, and microirghizites) of the Zhamanshin astrobleme in general and will provide information for the reconstruction of the impact event.

Theoretical modeling of the magnetic properties of Fe3O4-Fe3-xTixO4 composites obtained by the sol-gel method with subsequent hydrothermal treatment has been carried out. The magnetization reversal fields and the number of particles in different magnetic states of an ensemble of two-phase particles with an infinitely thin boundary between the phases and a characteristic size varying in the range from 30 to 80 nm were calculated using the "magnetic rectangles" method. Hysteresis characteristics of an ensemble of chemically inhomogeneous magnetostatically interacting particles were obtained, consistent with experimental data.

Theoretical modeling of the magnetic properties of Fe 3 O 4 -Fe 3-x Ti x O 4 composites obtained by the sol-gel method with subsequent hydrothermal treatment has been carried out. The magnetization reversal fields and the number of particles in different magnetic states of an ensemble of two-phase particles with an infinitely thin boundary between the phases and a characteristic size varying in the range from 30 to 80 nm were calculated using the "magnetic rectangles" method. Hysteresis characteristics of an ensemble of chemically inhomogeneous magnetostatically interacting particles were obtained, consistent with experimental data. Keywords: Composites, magnetic granulometry, micromagnetism, two-phase particles, magnetostatic interaction.

The study of impact glasses from the Zhamanshin meteorite crater has a long history extending back to early 1970ies. Most attention is paid to unique impact-related rocks known as zhamanshinites (bombs) and irghizites (lapilli). But, as first shown by V.L. Masaitis, other, more common types of impactites, suevites and massive melts (tagamites), are also present in Zhamanshin. We study the distribution in the crater, structure and composition of these particular rocks using powder X-ray diffraction and scanning electron microscopy. It is shown that all impact glasses from the Zhamanshin crater are genetically related and derive from the impact event, while the observed petrographic differences between them reflect the conditions of their formation. Individual varieties of studied impactites (suevites and tagamites) are spatially separated and, as a rule, do not intersect. This points to the absence of global mixing of the target material as a result of the impact event, as well as to the complex nature of the impactor.

To evaluate the effect of undersaturation of magnetic hysteresis loops measured in moderate (<2 T) fields in magnetically hard minerals such as goethite or hematite, we measured room temperature hysteresis loops in a 7 T field and DC backfield demagnetization curves in fields up to 3 T using an MPMS 3 instrument. Sediments from different regions of the East European platform, mostly of Carboniferous age were used for this study. Similar experiments were also carried out for a small collection of archaeological ceramics (bricks) apparently containing a High Coercivity Low unblocking Temperature (HCLT) magnetic phase (ε-Fe2O3?). Hysteresis measurements were complemented by thermomagnetic analysis at low and high temperatures, microscopic observations, and X-ray diffraction studies. High-field magnetic hysteresis loops alone appear insufficient to definitively discriminate goethite from hematite, though there is, expectedly, a tendency that increasing goethite content leads to magnetic hardening, with coercive force reaching 1 T and coercivity of remanence 1.7 T. At the same time, ε-Fe2O3 can seemingly be distinguished from either hematite or goethite due to its high saturation magnetization. However, combining hysteresis measurements with low- and high-temperature thermomagnetic analysis provides a much better insight into the magnetic mineralogy of samples. Still, acquiring the reference data on well characterized hematite, goethite, and ε-Fe2O3 samples is highly desirable.

Magnetic properties, structure, and phase composition of samples of ferruginous rocks from the Zhamanshin meteorite crater have been investigated. X-ray phase analysis, microscopy and magnetometry have revealed that studied rocks can be considered as a fine-grained polymictic sandstone which undergone significant alteration. All samples appear highly ferruginous, with cement of goethite with small particles of the matrix. Detrital grains are quartz, feldspar, rarely mica, as well as monazite, ilmenite, zircon, and cassiterite in accessory quantities. Inclusions of glass, probably of impact origin, with low silica, high alumina, and high iron content have also been encountered. A characteristic feature of goethite is the presence of Mn and a pronounced zonal structure manifesting itself in an increased Al content. Intergrowths and druses of authigenic magnetite are found in voids and cracks; magnetite however appears completely by iron (hydr)oxides. These observations generally agree with the paleogeographic data, and suggest that the crater and its vicinity experienced significant changes of the redox regime in the post-impact time.

A comprehensive study of the magnetic behavior, morphology, and composition of Fe-containing oxide coatings on aluminum and titanium has been carried out to investigate the origin of their ferromagnetism. The coatings have been formed by the plasma electrolytic oxidation (PEO) technique in slurry electrolytes containing colloidal particles of iron(III) hydroxides. On the surface of coatings on Al, iron is distributed unevenly concentrating in defective areas with a large number of small pores, and near large pores. On the surface of coatings on Ti, iron and titanium are distributed in antiphase in areas of comparable size. Within the pores, iron concentration appears about 5-10 times higher and oxygen concentration 3-4 times lower than their average concentration over the surface. In both cases, localization of the areas with ferromagnetic properties follows the peculiarities of iron distribution on the surface. The magnetic fraction in the coatings on aluminum appears to be represented by iron-aluminum spinel Fe3-xAlxO4 with x > 0.06, likely cation-deficient. Elemental iron and traces of iron hydroxides are also possibly present. In the coatings on titanium, titanomagnetite (Fe3-xTixO4, where x similar to 0.2-0.3) or its oxidized analogue, titanomaghemite, appear to be present, and possibly also some Fe-Ti alloy particles. (C) 2019 Elsevier B.V. All rights reserved.

Composites Fe m O n –Fe 3 – x Ti x O 4 have been synthesized using the sol–gel method and hydrothermal treatment. The conditions chosen for the synthesis favor the formation of composites containing titanomagnetite in a relatively low concentration. The theoretical analysis of the magnetic properties of the composites is performed based on the hysteresis curves and the temperature dependences of the remanent magnetization using the cluster model of magnetostatically interacting two-phase particles.

In this work, the materials of FemOn – Fe3-xTixO4 composition have been obtained using the sol-gel method and hydrothermal treatment. The synthesis conditions favor the formation of composites containing titanomagnetite in a rather low concentration. Based on the hysteresis curves and temperature dependences of the remanent magnetization, theoretical analysis of the composites magnetic properties has been carried out using a model of clustered two-phase particles bound with magnetostatic interaction.

Composites FemOn–Fe3 – xTixO4 have been synthesized using the sol–gel method and hydrothermal treatment. The conditions chosen for the synthesis favor the formation of composites containing titanomagnetite in a relatively low concentration. The theoretical analysis of the magnetic properties of the composites is performed based on the hysteresis curves and the temperature dependences of the remanent magnetization using the cluster model of magnetostatically interacting two-phase particles.

The results are presented from studying the structural phase composition of inclusions in irghizites (tektite-like impact glasses from the Zhamanshin astrobleme). The presence of micron and submicron crystalline iron-bearing minerals is detected. These are spheroids, skeletal aggregates, and crystals of unusual structure and complex composition.