Directional crystallization and self-assembling initiated by mechanical shock or electron beam in nanocrystalline Co-C and Fe-C films

We investigated iron and cobalt films with 20% carbon concentration with nanocrystalline structure. One of the aims of this work is to analyze the physical nature of high-speed structural self-assembling as often happens in explosive crystallization processes in these films.     

Faraday effect in nanogranular Co-Sm-O films

The Faraday effect (FE) was studied in Co-Sm-O composite films consisting of nanoparticles of metallic cobalt embedded in a samarium oxide dielectric matrix. The volume of the magnetic phase was ～60%. The FE spectral dependence for the condensates studied revealed a substantial change as compared to that for bulk cobalt samples, as well as for the films of nanocrystalline Co and CoSm films prepared in this study. An enhancement of the FE was also observed in the short-wavelength part of the optical spectrum.     

Nanocrystalline cobalt films prepared under ultrafast condensation conditions

The magnetic and electrical properties and the temperature dependence of these properties of cobalt films prepared at high condensation rates (10⁵–10⁶ Å/s) are investigated. Incremented annealing reveals several nonequilibrium states of cobalt in transition from the asprepared metastable structure to the ordinary hcp structure. The anomalies of the properties are analyzed from the standpoint of the nanocrystalline state of the samples. Model concepts of microcluster formations in the investigated films are also discussed.     

Solid-phase synthesis of Co7Sm2(110) epitaxial nanofilms: Structural and magnetic properties

The solid-phase synthesis of the Co₇Sm₂ and Co₁₇Sm₂ magnetically hard phases in Co/Sm/Co(110) epitaxial film systems has been experimentally investigated. The Co₇Sm₂ phase is first formed at the Sm/Co interface at a relatively low (～300°C) temperature. As the annealing temperature increases to ～450°C, the Co₁₇Sm₂(110) phase grows epitaxially on the Co₇Sm₂(110) phase. The saturation magnetization and biaxial anisotropy constant in the samples vary with the formation of the Co₇Sm₂ and Co₁₇Sm₂ phases. Investigations of the solid-phase synthesis in the nanofilms reveal the existence of a new structure phase transition at 300°C in the Co-Sm system with a high cobalt content.     

Long-range chemical interactions in solid-state reactions: effect of an inert Ag interlayer on the formation of L10-FePd in epitaxial Pd(0 0 1)/Ag(0 0 1)/Fe(0 0 1) and Fe(0 0 1)/Ag(0 0 1)/Pd(0 0 1) trilayers

The effect of 0, 0.5, and 1?μm-thick Ag interlayers on the chemical interaction between Pd and Fe in epitaxial Pd(0?0?1)/Ag(0?0?1)/Fe(0?0?1)/MgO(0?0?1) and Fe(0?0?1)/Ag(0?0?1)/Pd(0?0?1)/MgO(0?0?1) trilayers has been studied using X-ray diffraction, ⁵⁷Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and magnetic structural measurements. No mixing of Pd and Fe occurs via the chemically inert Ag layer at annealing temperatures up to 400?°C. As the annealing temperature is increased above 400?°C, a solid-state synthesis of an ordered L1₀-FePd phase begins in the Pd(0?0?1)/Ag(0?0?1)/Fe(0?0?1) and Fe(0?0?1)/Ag(0?0?1)/Pd(0?0?1) film trilayers regardless of the thickness of the buffer Ag layer. In all samples, annealing above 500?°C leads to the formation of a disordered Fe_xPd_1?x(0?0?1) phase; however, in samples lacking the Ag layer, the synthesis of Fe_xPd_1?x is preceded by the formation of an ordered L1₂-FePd₃ phase. An analysis of the X-ray photoelectron spectroscopy results shows that Pd is the dominant moving species in the reaction between Pd and Fe. According to the preliminary results, the 2.2?μm-thick Ag film does not prevent the synthesis of the L1₀-FePd phase and only slightly increases the phase’s initiation temperature. Data showing the ultra-fast transport of Pd atoms via thick inert Ag layers are interpreted as direct evidence of the long-range character of the chemical interaction between Pd and Fe. Thus, in the reaction state, Pd and Fe interact chemically even though the distance between them is about 10⁴ times greater than an ordinary chemical bond length.     

CoPt–Al 2 O 3 Nanocomposite Films: Synthesis,Structure, and Magnetic Properties

The structure and magnetic properties of CoPt–Al2O3 nanocomposite films synthesized by the annealing of Al/(Co3O4 + Pt) bilayers on a MgO(001) substrate at 650°C in vacuum are investigated. The synthesized composite films contain ferromagnetic CoPt grains with an average size of 25–45 nm enclosed in a nonconducting Al2O3 matrix. The saturation magnetization (Ms ~ 330 G) and coercivity (Hc ≈ 6 kOe) of the films are measured in the film plane and perpendicular to it. The obtained films are characterized by a spatial rotational magnetic anisotropy, which makes it possible to arbitrarily set the easy magnetization axis in the film plane or perpendicular to it using a magnetic field stronger than the coercivity (H > Hc).     

Structural and Magnetic Characteristics of Nanogranular Co–Al2O3 Single- and Multilayer Films Formed by the Solid-State Synthesis

The results of structural and magnetic investigations of nanogranular Co–Al₂O₃ films formed from Co₃O₄/Al thin-film layered structures upon vacuum annealing are reported. The Co₃O₄/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O₂ gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al₂O₃ single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.

     

Spin-wave spectroscopy study of spatial magnetization fluctuations in metastable nanocrystalline films of Fe-based alloys

The spectrum of standing spin waves is investigated in nanocrystalline Fe films prepared by the pulsed plasma-spraying method. The dispersion relation of these waves is determined in the wave-vector range (0.2–3.2)×10⁶ cm^?1 and is found to be affected by spatial magnetization fluctuations 100 Å in size. These fluctuations are supported as being due to the inhomogeneous distribution of C atoms in the atomic structure of nanocrystalline Fe films.     

Thermoelastic vibrations of a Timoshenko microbeam based on the modified couple stress theory

Nonlinear Dynamics - The dependence of the quality factor of nonlinear microbeam resonators under thermoelastic damping for Timoshenko beams with regard to geometric nonlinearity has been studied....