Papers by Keyword: Magnetic Anisotropy

Abstract: This study describes a perspective using non-destructive testing of stress-strain state joints in underwater wet welding and air. High residual stresses after underwater wet welding may be a possible cause of arising corrosion processes and cold cracking in structures. Assessing residual stresses can introduce additional changes in the technological welding process and subsequent reducing stresses. Analysis of application magnetic anisotropy and X-ray diffraction methods are shown for discovering residual tensile stresses after surfacing on high strength steel. Two complementary methods make it possible to determine the magnitude and features of the distribution of residual welding stresses after underwater wet surfacing and air surfacing.

Abstract: An understanding of the magnetic properties in an amorphous alloy requires comprehensive studies of magnetic anisotropy at various scales. In this paper such a study is carried out using amorphous ribbons FeCuNbSiB. The magnetic anisotropy associated with the rolling axis of ribbons does not affect hysteresis loop measurements, but the disappearance of a fingerprint-like pattern in the domain structure occurs in different fields when they are applied along and transverse the rolling axis. A correlation between the local magnetic anisotropy constant and the nanoscale within which the local easy axis is ordered was found.

Abstract: Few Fe-Ni particles with composition close 50:50 were found by EDX and SEM investigations in the fragment of Chelyabinsk meteorite. These inclusions were extracted and magnetic domains were observed with the help of sol-gel method. No hard magnetic particles with tetragonal L1₀ crystal structure (tetrataenite) were detected.

Abstract: Orientation technique based on the magneto-scientific crystal alignment phenomenon combined with electrophoretic deposition (EPD) technique was applied for the seeding process of zeolite L particles. Well-dispersed, ethanol-based zeolite L suspension was prepared and then consolidated on porous zirconia substrates by EPD. Conducting polypyrrole film synthesized on the zirconia substrate was used as an anodic substrate for the EPD process. The EPD was performed in a superconducting magnet with applying 12 T strong magnetic field to the suspension. The degree of orientation was characterized by XRD and compared with that of the zeolite L layer prepared by slip casting in a 12 T strong magnetic field using the same suspension.

Abstract: New {[({[(Co₄₁Fe₃₉B₂₀)_X(SiO₂)_100X]/[(Co₄₁Fe₃₉B₂₀)_X(SiO₂)_100х+O₂]}₁₇₈ and {[(Co₄₅Fe₄₅Zr₁₀)_X(Al₂O₃)_100-X]/[(Co₄₅Fe₄₅Zr₁₀)_X(Al₂O₃)_100-X+O₂]}₃₀₀ multilayer heterogeneous structure has been obtained by ion-beam sputtering method. Magnetostatic and magnetodynamic properties and the structure of the nanocomposites have been investigated. It was shown that, the oxidized interlayer composite adding lead to suppression of perpendicular magnetic anisotropy component, and a change in the magnetic structure of the composites, which determines the change in the frequency dependence of the real (μ^/) and imaginary (μ^//) parts of the complex permeability.

Abstract: An ab initio study of Co monatomic nanowires (NW) magnetic properties on pure and oxygen reconstructed Cu (210) surface was performed. Strong influence of oxygen surface impurity on MAE in Co nanowire was found. High value of magnetic moment and small energy of magnetic anisotropy (MAE) were obtained in Co nanowires on pure Cu (210) surface. After oxygen reconstruction of Cu (210) surface (Cu (210)-(2×1)O) the significant enhancement of MAE was found in Co nanowires, while the magnetic moment of Co atoms is practically unchanged. Oxygen on Cu (210) surface rotates easy magnetization axis in Co NW with respect to the pure surface.

Abstract: The magnetic anisotropy (MA) of trihydrides of single-crystalline rare-earth (R) intermetallics R₂Fe₁₇H_3±x (R = Tb and Dy) with small deviations in the hydrogen concentration (x = 0 – 0.4) was investigated via the magnetic and magnetoelastic measurements in a wide temperature region. The easy-axis MA of Tb₂Fe₁₇H_3±x is preserved in the entire range of magnetically ordered state while an “easy-cone – easy-plane” transition takes place in Dy₂Fe₁₇H_3±x above ambient temperatures. The trihydrides demonstrate a significant decrease of magnetic anisotropy as the temperature increases. The temperature variation of thermal expansion of Dy₂Fe₁₇H₃ displays anomalies in the vicinity of a spin-reorientation transition. The longitudinal magnetostriction λ_||(T) of the same compound changes its sign at 340 K. The compounds studied can find specific applications in practice.

Abstract: Magnetic properties, structure and thermal stability of the (Fe_0.7Co_0.3)₈₈Hf₂W₂Mo₂Zr₁B₄Cu₁ alloy ribbon after its nanocrystallization at 620-750°C for 0-20 min in the presence or absence of tensile stresses σ were studied. It was shown that under the effect of tensile stresses a longitudinal magnetic anisotropy with an easy magnetization axis parallel to the long size of the ribbon was induced in the alloy. A better thermal stability of magnetic properties was observed for the alloy subjected to the nanocrystallization annealing at 620° for 20 min with σ = 170 MPa. After the subsequent annealing at 570°C for 25 h without σ, the magnetic properties of the alloy are unchanged. Increasing of the nanocrystallization annealing temperature up to 670-750°C did not result in improvement of the thermal stability of magnetic properties.

Abstract: 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.

Abstract: The present work has been undertaken to research effects of structure, morphology, volume fraction, spatial arrangement of magnetostrictive intermetallic FeGa alloy particles dispersed in modified polyurethane matrix. Correlation of composite magnetic behavior with structure and mechanical properties has been obtained by measurements of magnetostriction, remanent magnetization anisotropy, SEM, and dynamical mechanical analysis. Anisotropic chain structures of magnetic particles within the polymer with different interparticle interactions were observed. The increase of the magnetostrictive response with tailor-made magnetic anisotropy induced by magnetic particles volume fraction has been demonstrated