Fe3C-C core-shell nanoparticles were fabricated on a large scale by metal-organic chemical vapor deposition at 700 °C with ferric acetylacetonate as the precursor. Analysis results of x-ray diffraction, transmission electron microscope and Raman spectroscope showed that the Fe3C cores with an average diameter of ∼35 nm were capsulated by the graphite-like C layers with the thickness of 2-5 nm. The comparative experiments revealed that considerable Fe3O4-Fe3C core-shell nanoparticles and C nanotubes were generated simultaneously at 600 and 800 °C, respectively. A formation mechanism was proposed for the as-synthesized core-shell nanostructures, based on the temperature-dependent catalytic activity of Fe3C nanoclusters and the coalescence process of Fe3C-C nanoclusters. The Fe3C-C core-shell nanoparticles exhibited a saturation magnetization of 23.6 emu g(-1) and a coercivity of 550 Oe at room temperature.

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In this work, a novel multiferroic-like nanocomposite is designed and obtained using the high-pressure torsion (HPT) method. The crystal structure, phase composition, morphology, ferromagnetic (FM), and ferroelectric (FE) properties of the initial powders and ferroelectric/ferromagnetic nanocomposites are studied comprehensively. The initial powders and their composite show the perovskite and spinel crystalline phases for the FE and FM fractions, respectively. After HPT, the particle sizes of the initial powders are decreased significantly. It is shown that the novel nanocomposite consists of exchange-interacting FE and FM phases and demonstrates improved magnetic and electrical properties in low fields at room temperature. A giant increase in residual polarization with an increase in external high-pressure is found in new composite. The obtained results make it possible to consider the novel nanocomposite as a new functional material for its use both in electronic devices for monitoring ultra-high-pressure and in integrated circuits of high-speed computing nanosystems with low switching energy. The HPT method is a promising method for obtaining new heterophase nanosystems.

Structure, perovskite phase formation, chemical and phase composition, microstructure, morphology and dielectric properties of the single-phase lanthanum-modified bismuth ferrite multiferroic ceramics obtained by the rapid liquid-phase sintering method under different compacting pressures have been investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetry/differential thermal analysis and dielectric spectroscopy methods. The temperature and time for an express preparation of the single-phase Bi0.9La0.1FeO3 ceramics with formation of a perovskite structure have been found out. With an increase in the compacting pressure P from 100 to 1100 MPa, the dielectric constant ε′ changes by ∼25% and ∼80% in the low-frequency and ultra-high frequency ranges, respectively. In the low-frequency range, all samples depending on the pressure P demonstrate excellent dielectric behavior with a stable dielectric constant and quite low dielectric loss that make these samples perspective for their possible practical application in microelectronic and spintronic.

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