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We calculate electronic structure and spin susceptibility dependencies on doping within the framework of a cluster perturbation theory for strongly correlated electronic systems. The change in the susceptibility with increasing doping is qualitatively consistent with the experimental data on resonant inelastic X-ray scattering and inelastic neutron scattering, as well as with the results of the calculations within the quantum Monte Carlo method. [ABSTRACT FROM AUTHOR]

Nanoparticles of Co1 –xMgxFe2O4 with x equal to 0, 0.2, 0.4, 0.6, 0.8, and 1.0 have been synthesized. For all values of x, they are nanocrystals with a cobalt ferrite structure and an average linear size ( nm. Based on the analysis of the Mössbauer effect spectra, the Co2+ ions were shown to occupy only octahedral positions at all values of x. The experimentally obtained dependence of the nanoparticles magnetization on x corresponds to the dependence calculated using the Mössbauer effect data, except for the sample with . The effective magnetic anisotropy constant estimated for 0 K from the analysis of the coercive force temperature dependences decreases from at to erg/cm3 at and drops sharply to erg/cm3 at . [ABSTRACT FROM AUTHOR]

Auger electron spectroscopy was used to determine the phase composition of Cr2GeC MAX phase thin films. A distinctive feature of the formation of carbon-containing MAX phases is the shape of carbon Auger peaks, which is characteristic of metal carbides spectra. Features of the Auger spectra in the presence of secondary phases of chromium germanides are found. Their presence can manifest itself in an increase in the energy of the germanium peaks, which is caused by a chemical shift during the formation of the Cr–Ge bond. Moreover, we have detected the accumulation of electronic charge, which can be explained by the features of the surface morphology. [ABSTRACT FROM AUTHOR]

Cu2FeBO5 ludwigite single crystals have been grown from a solution–melt by spontaneous crystallization. Using the X-ray diffraction method, the crystal structure has been resolved in detail. Cations in sites M2, M3, and M4 have turned out to be structurally disordered. It has been found that oxygen atoms are disordered in one of five nonequivalent sites (O4). As can be seen from Mössbauer spectroscopy data, Fe3+ ions occupy four nonequivalent sites with different distortions of coordination octahedra. In the temperature range 40 K ≤ T ≤ 300 K, the spectra represent a superposition of quadrupole doublets. Static susceptibility measurements have revealed two magnetic features at T1 = 35 K and T2 = 20 K and spin-glass effects. Specific heat measurements in the interval 4–300 K have not discovered magnetic-transition-related anomalies. [ABSTRACT FROM AUTHOR]

A spin-crossover mechanism in ludwigite Со3BO5 is proposed on the basis of the DFT calculation with SCAN potentials. The role of separate exchange interactions in the establishment of the long-range magnetic order is demonstrated within the Monte Carlo method. [ABSTRACT FROM AUTHOR]

Magnetization dependences of CoxZn1 –xFe2O4 nanoparticles ( , 0.1, 0.2, 0.3, 0.4, 0.5) synthesized with the citrate precursor technique on an external magnetic field and temperature are presented. Ferrimagnetic order in nanoparticles with appeared at temperatures, T, exceeding room temperature, and in nanoparticles with and 0.1 at T near 100 K. The saturation magnetization, , remnant magnetization, , and the coercive force, , increase with x increase and the temperature decrease. reached very high value: of NPs with equals to 106.6 emu/g at 100 K while, according to the literature data, of stoichiometric bulk Co ferrite equals to 90 emu/g at 4.2 K. Correlations between concentration dependences of magnetic and electric properties has been revealed and explained qualitatively. [ABSTRACT FROM AUTHOR]

Changes in the magnetic properties of FeBO3 single crystals in the course of spin crossover occurring with increasing pressure up to 63 GPa are studied both experimentally and theoretically. Simultaneous measurements of the nuclear diffraction and nuclear forward scattering spectra make it possible to detect the antiferromagnetic high-spin state at low pressures up to 48 GPa and to reveal the antiferromagnetic state within the range characterized by the coexistence of Fe3+ ions in the high-spin and low-spin states, which occurs at pressures from 48 to 54 GPa, where the hysteresis takes place. Above 58 GPa, only the low-spin state is observed, whereas the magnetic order is absent down to 9 K. An analysis of changes in the exchange interactions manifesting themselves at spin crossover suggests that there exist competing ferromagnetic and antiferromagnetic contributions nearly compensating each other. A possible Néel temperature in the low-spin state does not exceed 7 K; thus, an ordered state cannot be observed in our experiments. [ABSTRACT FROM AUTHOR]

The ac transport properties of a Fe/SiO2/n-Si MIS structure made in the form of a Schottky diode have been studied in magnetic fields up to 9 T. A shift in the maxima of the temperature dependences of the impedance real part observed in the magnetic field is accompanied by the magnetoimpedance effect and takes place only at a certain relative orientation between the magnetic field and the surface of the sample. It has been found that the magnetoimpedance effect is related to the recharge of impurity states. Impurity state energy Es in the presence and absence of the magnetic field has been calculated. The impurity state energy is a nonlinear function of magnetic field and can be qualitatively characterized in terms of the theory of the Zeeman giant effect in diluted magnetic semiconductors. Other mechanisms of magnetic field influence on ac transport in MIS structures, specifically, on the impurity state recharge, cannot be disregarded either. This points calls for further investigation. Obtained data may provide a deeper insight into the nature of magnetoresistive effects in semiconductors and be used to design new-generation microelectronic devices. [ABSTRACT FROM AUTHOR]

The possibility of growth of thin Mn2GaC MAX phase films on Al2O3 substrates with various orientations and their magnetic properties have been studied. The most favorable orientation relationships and interface planes in the Mn2GaC//Al2O3 system, which indicate the possibility of growth on C-face (0001), S-face , N‑face , and R-face sapphire substrates, have been predicted within a geometric approach. Using the electron density functional method, the possible magnetic properties of continuous ultrathin Mn2GaC films have been calculated under the condition of conservation of uniform expansions/compressions of the MAX phase lattice, which are induced by growth on the predicted substrates. The effect of the deformation of the Mn2GaC lattice on magnetic ordering and magnetic moments has been determined, and the possibility of a transition from an antiferromagnetic to a ferromagnetic state under the action of external magnetic fields has been evaluated. It has been shown that the growth of the ferromagnetic film of the Mn2GaC MAX phase is the most probable on the Al2O3 (0001), Al2O3 , and Al2O3 substrates. [ABSTRACT FROM AUTHOR]

MAX phases are a family of ternary layered compounds with formal stoichiometry M2AX and have a layered hexagonal structure. Calculations with the B3LYP density functional show that, by varying the ratio between the chromium and iron in the MAX phase (Cr4 – xFex)0.5SiC, it is possible to change the lattice parameters and the magnetic moment on metal atoms. In this phase, a partial substitution of one metal for the other can be considered a technique of intended variation of their magnetic properties. [ABSTRACT FROM AUTHOR]

An unconventional temperature dependence of infrared absorption spectra of rare-earth cobalt oxides LaCoO3 and GdCoO3 has been studied experimentally and theoretically in the temperature range of 3.2–550 K. A quite strong softening of the optical phonon mode has been detected, which cannot be explained by standard lattice anharmonicity. It has been shown that the redshift of the phonon spectrum is due to the e-lectron–phonon coupling quadratic in the lattice displacement and to fluctuations of the multiplicity of Co3+ ions. [ABSTRACT FROM AUTHOR]

The article discusses the results of soil-geochemical studies carried out on the territory of the Chelyabinsk urban district. The features of the profile distribution of pollutants within the landscape catena are established. The maximum concentrations of heavy metals are confined to the upper soil horizons of the eluvial position under forest vegetation. The soils of the superaquatic position under moist meadow and swamp vegetation are less polluted. The most polluted soil layer is located at a depth of 4-10 cm from the surface. This may be due to a decrease in heterogeneous emissions from the city’s metallurgical enterprises over the past 30 years.

A spin-crossover mechanism in ludwigite Со3BO5 is proposed on the basis of the DFT calculation with SCAN potentials. The role of separate exchange interactions in the establishment of the long-range magnetic order is demonstrated within the Monte Carlo method. [ABSTRACT FROM AUTHOR]