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The combination of photothermal and magnetic functionalities in one biocompatible nanoformulation forms an attractive basis for developing multifunctional agents for biomedical theranostics. Here, we report the fabrication of silicon–iron (Si-Fe) composite nanoparticles (NPs) for theranostic applications by using a method of femtosecond laser ablation in acetone from a mixed target combining silicon and iron. The NPs were then transferred to water for subsequent biological use. From structural analyses, it was shown that the formed Si-Fe NPs have a spherical shape and sizes ranging from 5 to 150 nm, with the presence of two characteristic maxima around 20 nm and 90 nm in the size distribution. They are mostly composed of silicon with the presence of a significant iron silicide content and iron oxide inclusions. Our studies also show that the NPs exhibit magnetic properties due to the presence of iron ions in their composition, which makes the formation of contrast in magnetic resonance imaging (MRI) possible, as it is verified by magnetic resonance relaxometry at the proton resonance frequency. In addition, the Si-Fe NPs are characterized by strong optical absorption in the window of relative transparency of bio-tissue (650–950 nm). Benefiting from such absorption, the Si-Fe NPs provide strong photoheating in their aqueous suspensions under continuous wave laser excitation at 808 nm. The NP-induced photoheating is described by a photothermal conversion efficiency of 33–42%, which is approximately 3.0–3.3 times larger than that for pure laser-synthesized Si NPs, and it is explained by the presence of iron silicide in the NP composition. Combining the strong photothermal effect and MRI functionality, the synthesized Si-Fe NPs promise a major advancement of modalities for cancer theranostics, including MRI-guided photothermal therapy and surgery. [ABSTRACT FROM AUTHOR]

First-principles calculations of the stability, electronic, and magnetic properties of full-Heusler compound V2FeSi and Fe2VSi in regular ( L 2 1 ) and inverse ( X A ) structures have been performed using density functional theory within an SCAN meta-GGA functional. It is found that the X A crystal lattice is energetically more favorable for V2FeSi, while Fe2VSi forms the L 2 1 structure. In both cases, the electronic structure of the energetically stable modifications corresponds to half-metallic ferrimagnets. Magnetic properties of energetically favorable structures obey the Slater–Pauling rule. All considered properties of the studied structures are explained within the crystal orbital Hamilton population analysis. [ABSTRACT FROM AUTHOR]

Direct determinations of the isothermal entropy increment, -△ST, in the Heusler alloy Ni50CoMn36Sn13 on demagnetization gave positive values, corresponding to a normal magnetocaloric effect. These values contradict the results derived from heat-capacity measurements and also previous results obtained from magnetization measurements, which indicated an inverse magnetocaloric effect, but showing different values depending on the technique employed. The puzzle is solved, and the apparent incompatibilities are quantitatively explained considering the hysteresis, the width of the martensitic transition and the detailed protocol followed to obtain each datum. The results show that these factors should be analyzed in detail when dealing with Heusler alloys. [ABSTRACT FROM AUTHOR]

Structural, electronic, and magnetic properties of Mn2Co1-xVxZ (Z = Ga, Al, x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys were theoretically investigated for the case of L21 (space group Fm 3 ¯ m), L21b (L21 structure with partial disordering between Co and Mn atoms) and XA (space group F 4 ¯ 3m) structures. It was found that the XA structure is more stable at low V concentrations, while the L21 structure is energetically favorable at high V concentrations. A transition from L21 to XA ordering occurs near x = 0.5, which qualitatively agrees with the experimental results. Comparison of the energies of the L21b and XA structures leads to the fact that the phase transition between these structures occurs at x = 0.25, which is in excellent agreement with the experimental data. The lattice parameters linearly change as x grows. For the L21 structure, a slight decrease in the lattice constant a was observed, while for the XA structure, an increase in a was found. The experimentally observed nonlinear behavior of the lattice parameters with a change in the V content is most likely a manifestation of the presence of a mixture of phases. Almost complete compensation of the magnetic moment was achieved for the Mn2Co1-xVxZ alloy (Z = Ga, Al) at x = 0.5 for XA ordering. In the case of the L21 ordering, it is necessary to consider a partial disorder of atoms in the Mn and Co sublattices in order to achieve compensation of the magnetic moment. [ABSTRACT FROM AUTHOR]

We calculated the electron susceptibility of rare-earth tritelluride compounds RTe3 as a function of temperature, wave vector, and electron-dispersion parameters. Comparison of the results obtained with the available experimental data on the transition temperature and on the wave vector of a charge-density wave in these compounds allowed us to predict the values and evolution of electron-dispersion parameters with the variation of the atomic number of rare-earth elements (R). [ABSTRACT FROM AUTHOR]

We report a numerical study of the field assisted sintering of silicon germanium alloys by a finite element method, which takes into account contact resistances, thermal expansion and the thermoelectric effect. The distribution of electrical and thermal fields was analyzed numerically, based on the experimental data collected from spark plasma sintering (SPS) apparatus. The thermoelectric properties of Si-Ge used within the simulation were considered as the function of density and the sintering temperature. Quantitative estimation of the temperature distribution during the sintering pointed to a significant, up to 60 °C, temperature difference within the specimen volume for the case of the sintering temperature at 1150 °C. [ABSTRACT FROM AUTHOR]