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We described the synthesis method and presents the results of a study of the magnetic and magnetotransport properties of vertical hybrid structures Fe3Si/Ge/Mn5Ge3/Si. The mechanisms responsible for the detected magnetoresistive effect and the possible contribution of the spin-valve effect, realized through spin injection/extraction into/from germanium, are discussed. [ABSTRACT FROM AUTHOR]

Mn5Ge3 is a ferromagnetic hexagonal crystal promising for spintronics and magnetocalorics. A systematic study and analysis of the magnetic properties of the Mn5Ge3 thin film grown on Si(111) were performed. The magnetic anisotropy of the film is determined by the shape anisotropy and the easy magnetization axis aligned along the c axis of the crystal. The uniaxial anisotropy constant Ku fully corresponds to that for a bulk single crystal, which indicates that c axis coincides with film normal. Mn5Ge3 film demonstrates high saturation magnetization MS = 900 emu/cm3 (900 kA/m) at T = 100 K and magnetocaloric effect ΔS = 3.16 ± 0.22 J kg−1 K−1 at 300 K and B = 1.5 T. ΔS is comparable to that for multicomponent or Gd rare earth films. Furthermore, a different anisotropy of the magnetocaloric effect compared to bulk Mn5Ge3 was found, which may be related to the anisotropy of the film shape and, possibly, to the domain structure. The results obtained are promising for the design and development of magnetocaloric, spintronic, and spin-caloritronic devices on a silicon platform. [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]

Fe3O4@C, Fe3O4@C@C, and Fe3O4@SiO2 core–shell nanoparticles are synthesized via thermal decomposition and coprecipitation. Samples are characterized via X-ray spectroscopy, transmission electron microscopy, and magnetometry. It is shown that the magnetic core of all nanoparticles is nanocrystalline and has crystal parameters corresponding to only one phase of Fe3O4, covered with a uniform shell of amorphous carbon or silicon oxide around 8 nm thick. Special attention is given to adsorption properties of the nanoparticles with respect to four dyes: Methylene blue, Congo Red, Eosin Y, and Rhodamine C. The high selectivity of Fe3O4@C nanoparticles to various dyes is revealed. [ABSTRACT FROM AUTHOR]

The morphology, structure, and magnetic properties of Fe3O4 and Fe3O4@C nanoparticles, as well their effectiveness for organic dye adsorption and targeted destruction of carcinoma cells, were studied. The nanoparticles exhibited a high magnetic saturation value (79.4 and 63.8 emu/g, correspondingly) to facilitate magnetic separation. It has been shown that surface properties play a key role in the adsorption process. Both types of organic dyes—cationic (Rhodomine C) and anionic (Congo Red and Eosine)—were well adsorbed by the Fe3O4 nanoparticles' surface, and the adsorption process was described by the polymolecular adsorption model with a maximum adsorption capacity of 58, 22, and 14 mg/g for Congo Red, Eosine, and Rhodomine C, correspondingly. In this case, the kinetic data were described well by the pseudo-first-order model. Carbon-coated particles selectively adsorbed only cationic dyes, and the adsorption process for Methylene Blue was described by the Freundlich model, with a maximum adsorption capacity of 14 mg/g. For the case of Rhodomine C, the adsorption isotherm has a polymolecular character with a maximum adsorption capacity of 34 mg/g. To realize the targeted destruction of the carcinoma cells, the Fe3O4@C nanoparticles were functionalized with aptamers, and an experiment on the Ehrlich ascetic carcinoma cells' destruction was carried out successively using a low-frequency alternating magnetic field. The number of cells destroyed as a result of their interaction with Fe3O4@C nanoparticles in an alternating magnetic field was 27%, compared with the number of naturally dead control cells of 6%. [ABSTRACT FROM AUTHOR]

A comprehensive study is performed of the properties of hybrid structures of iron oxide and reduced graphene oxide α-Fe2O3/rGO synthesized via "wet mixing." It is shown that hematite nanoparticles with a comparatively uniform distribution can be encapsulated in graphene layers, and the way of preparing precursors is of critical importance in shaping the magneto-optical properties of α-Fe2O3/rGO hybrid structures. [ABSTRACT FROM AUTHOR]

Magnetic circular dichroism and polarized optical absorption spectra of single-crystal DyFe3(BO3)4 were measured in the region of the crystal transparency from 8700 to 16 000 cm−1 in the temperature range from 90 K up to room temperature. Spectra of d-d and f-f transitions were separated, and f-f transitions 6H15/2 → 6(F9/2+H7/2), 6F7/2, 6F5/2, and 6F3/2 were studied. From these measurements, temperature dependences of the paramagnetic magneto-optical activity (MOA) of the electric dipole-forbidden f-f transitions were obtained. It was revealed that, in contrast to allowed transitions, temperature dependences of the MOA of some f-f transitions substantially deviate from the Curie-Weiss law. The theories of MOA of allowed and f-f transitions were considered and the experimental results obtained were accounted for. Circular polarizations in magnetic field and linear polarizations of absorption lines were determined. The Zeeman splitting of some absorption lines were found. Symmetries of the crystal field states were analyzed on the bases of the obtained results in D3 local symmetry approximation. A small splitting (≈16.5 cm−1) between the two lowest sublevels of the ground manifold was detected, and symmetries of these states were identified as E1/2 (M = ±13/2) and E3/2 (M = ±15/2), respectively. Deviation of the local symmetry of the Dy3+ ion from D3 is small, and it was revealed that polarizations of the majority of absorption lines can be accounted for in the D3 symmetry. This also testifies that in the process of some other electron transitions, the equilibrium configuration of the local environment deviates from D3 symmetry stronger than it does in the ground state. In addition, it has been shown that the distortions depend not only on the excited but also on the initial state. [ABSTRACT FROM AUTHOR]

The conditions for synthesis of Yb x Tm1 − x Al3(BO3)4 ( x = 0, 0.1, 0.2, 1.0) single crystals from fluxes based on bismuth trimolybdate Bi2Mo3O12 and lithium molybdate Li2MoO4 are investigated. It is proposed to grow them by the group method on seeds. The polarized optical absorption spectra are measured for two mutually orthogonal linear polarizations at temperatures of 100 and 300 K. [ABSTRACT FROM AUTHOR]