I. V. Nemtsev

Reversible UV induced metal–semiconductor transition in In2O3 thin films prepared by autowave oxidation

We have prepared thin indium oxide films by the autowave oxidation reaction. Measurements of temperature dependence of resistivity, Hall carrier concentration and Hall mobility have been conducted in the temperature range 5–272 K. Before ultraviolet (UV) irradiation, the indium oxide film had a semiconductor-like temperature dependence of resistivity ρ and the ratio of ρ (5 K)/ρ(272 K) was very limited (∼1.2). It was found that after UV irradiation of the In2O3 film, the metal–semiconductor transition (MST) was observed at ∼100 K. To show that this MST is reversible and repeatable, two full cycles of ‘absence of MST–presence of MST’ have been done using UV irradiation (photoreduction) as the induced mechanism and exposure to an oxygen environment as the reversible mechanism, respectively. MST in transparent conducting oxide (TCO) is possibly associated with the undoped structure of metal oxide, which has some disorder of oxygen vacancies. It was suggested that reversible UV induced metal–semiconductor transition would occur in other TCOs.

Solid-state synthesis of the ZnO-Fe 3 O 4 nanocomposite: Structural and magnetic properties

The structural and magnetic properties of ZnO-Fe3O4 nanocomposites produced by the solid-state reaction Zn + 3Fe2O3 → ZnO + 2Fe3O4 upon annealing of Zn/α-Fe2O3 films under vacuum at a temperature of 450°C have been studied. Ferrimagnetic Fe3O4 clusters with an average grain size of 40 nm and a magnetization of ∼430 emu/cm3 at room temperature, which are surrounded by a ZnO layer with a large contact surface, have been synthesized. The magnetic characteristics of the ZnO-Fe3O4 nanocomposite in the temperature range of 10–300 K have been presented.

Magnetic and Structural Properties of Granular Films Al2O3-FePd3 Synthesized by Aluminothermy

The Al2O3-FePd3 structure was fabricated by aluminothermy, or the Goldschmidt reaction. The initial structure was prepared by the formation of a highly-ordered L10-FePd epitaxial film with the use of the solid-state reaction in a Fe(001)/Pd(001) bilayer system on the MgO substrate. To obtain a granular structure, the L10-FePd samples were oxidized in air with the subsequent deposition of an aluminum layer onto their surface and vacuum annealing. Depending on annealing time and temperature, a system of L12-FePd3 grains 5 nm in size was formed in an Al2O3 insulating matrix. Parameters of thermal treatment of the initial structure are presented, the occurring phase transformations are described, and the magnetic characteristics are measured. It is established that the ordered L10-FePd phase is obtained at an initiation temperature of the reaction of about 450 оС and the granular L12-FePd3 system forms at 600-650 °С.

Magnetic Anisotropy of Co-Nanostructures Embedded in Matrices with Different Pores Size and Morphology

Composite materials with Co (P) particles embedded into pores of silica and track etched polycarbonate membranes were fabricated by an electroless reduction. The magnetic and structural properties of the composite materials are characterized by scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer. The macroscopic and local magnetic anisotropy of the Co (P) particles electroless deposited in the pores of the polycarbonate membrane and silica is studied. The composite materials with linear pores exhibit uniaxial magnetic anisotropy. The easy axis lies along the Co (P) rods, the shape anisotropy dominates over the intrinsic crystalline anisotropy. Information on local anisotropy field and the grain size was obtained from investigation of approach to saturation magnetization law. The local anisotropy field for all the samples depends on P content. For Co (P) rods the local anisotropy value is also determined by nominal pore sizes. It was found that the investigated Co (P) rods is nanocrystalline. The effects of different pores morphology on the FMR-spectra characteristics are studied.

Ferromagnetic resonance linewidth in powders consisting of core–shell particles

The dependence of the ferromagnetic resonance linewidth on the thickness of nonmagnetic shells in powders consisting of ferromagnetic core–nonferromagnetic shell composite particles is investigated. It is found that an increase in shell thickness reduces the ferromagnetic resonance linewidth by several times, down to values comparable to those for coatings with compositions similar to that of the particle’s core. The observed effect is assumed to result from suppression of the inhomogeneity of demagnetizing fields in a powder consisting of magnetic particles.

Nanodispersed Powders of Fe-Ni Particles with Carbon Shell

УДК 539.2:533.9(07) Nanodispersed Powders of Fe-Ni Particles with Carbon Shell Grigory N. Churilov,∗ Natalia G.Vnukova Kirensky Institute of Physics Federal Research Center KSC SB RAS Akademgorodok, 50/38, Krasnoyarsk, 660036 Siberian Federal University Svobodny, 79, Krasnoyarsk, 660041 Russia Nikita S. Nikolaev† Siberian Federal University Svobodny, 79, Krasnoyarsk, 660041 Russia Gari A. Glushenko, Irina V. Osipova, Vladislav A. Lopatin Sergey V.Komogortsev, Dmitry A.Velikanov Mikhail N. Volochaev‡ Kirensky Institute of Physics Federal Research Center KSC SB RAS Akademgorodok, 50/38, Krasnoyarsk, 660036 Russia Ivan V. Nemtsev§ Krasnoyarsk Scientific center SB RAS Akademgorodok, 50, Krasnoyarsk, 660036 Russia

Magnetostructural investigations of bulk nanostructured (Со–Р)100–x Сu x alloys

Magnetostructural investigations of bulk nanostructured Co–P/Cu composites prepared by dynamic compacting are performed. The magnetic microstructure of the obtained materials is characterized. It is shown that the use of composite particles allows us to create bulk materials with the structures and main magnetic properties of the initial powders.

Cobalt-based bulk nanostructured materials prepared via the dynamic compacting of core–shell composite particles

Bulk nanostructured Co–P/Cu and Al2O3/Co–P composites are fabricated via dynamic compaction. The initial core–shell particles are synthesized by means of chemical deposition. Structural and magnetic characteristics of the composites are investigated. It is shown that the use of composite particles allows homogeneous compacts with the structure and magnetic characteristics of initial powders to be obtained.

Magnetic and Structural Properties of Nanocomposite ZnO-Fe3O4 Films Prepared by Solid-State Synthesis

A simple method for obtaining ZnO-Fe3O4 nanocomposites using solid-state reaction Zn + 3Fe2O3 ZnO + 2Fe3O4 is suggested. An analysis of the characteristics and properties of ZnO-Fe3O4 nanocomposites was carried out by a combination of structural and physical methods (X-ray diffraction, scanning electron microscopy, photoelectron spectroscopy, Mössbauer measurements, X-ray fluorescent analysis, and magnetic measurements). The magnetization of the hybrid ZnO-Fe3O4 films is equal to 440 emu/cm3. The resulting Fe3O4 nanoparticles are surrounded by a ZnO shell and have sizes ranging between 20 and 40 nm.

Synthesis of 6H-SiC single-crystal nanowires in a flow of carbon-silicon high-frequency arc plasma

Silicon carbide 6H-SiC nanoparticles and nanowires were obtained in carbon-silicon high-frequency arc plasma plasma in a helium atmosphere at a pressure of 0.1–0.6 MPa. It was shown that 6H-SiC nanowires grow from the arc plasma, as well as from the vapor, according to the known mechanism of vapor-solid condensation on a cold surface covered with single-crystal silicon carbide nuclei. The content of silicon carbide nanowires in the condensate reached 60 wt %. The obtained single-crystal silicon 6H-SiC nanowires had the diameter of 15–18 nm and length of 200–600 nm.