Papers by Keyword: FINEMET

Abstract: Using the methods of spectral analysis with application of the formalism of the integral function of Lebesgue measures and Kullback's divergence, the structural features of the interfaces of spinning Fe- (Cu, Nb) - (Si, B) tapes with different metalloid contents are investigated. An increase in the total concentration of the metalloid ambiguously affects the nature of the morphology of rapidly quenched alloys. The minimum difference in the statistics of contact and free surfaces, formed in the spinning process, is demonstrated by fusionFe₇₄Cu₁Nb₃Si₁₆B₆.

Abstract: This work aims provide an experimental overview of results revealing a unique phenomenon such as non-stochastic changes of the local composition and ordering of the metal-elements within alloys. A necessary and sufficient condition for the occurrence of this phenomenon is the charging with hydrogen the structure of the materials. Interestingly the element distribution changes are observed at room temperature and after a rather long rest time from the initial hydrogen insertion. The changes of positions and environments of the elements yield changes in phase compositions. This effect was observed in both amorphous and crystallized compounds, here we will report on the first category of materials, in particular Finemet alloys. The phenomenon was investigated using various experimental techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM).

Abstract: The microrelief of the contact, free sides and cuts of three metal alloys with various niobium contents were studied. It is shown that samples with high niobium content are X-ray amorphous, the alloys FeCu₁Si₁₆B₆, FeCu₁Nb₃Si₁₆B₆are characterized by an amorphous-crystalline structure. The change in the magnetic characteristics and electrical resistance of alloys in the course of thermomagnetic annealing is studied. It is shown that an increase in the Nb content in an alloy increases its temperature stability and the temperature of the onset of crystallization processes.

Abstract: Thin films of FeCuNbMoSiB have been sputtered on Corning glass substrates with thicknesses varying from 10 to 200 nm with post annealing at 450 °C and 550 °C. Annealing in the presence of the magnetic field applied along the plane of a substrate develops an uniaxial magnetic anisotropy with the in-plane easy axis. Estimation of the effective anisotropy constant from the magnetization measurements gave K_eff = 3.23 kJ/m³. Structure and surface of the films were investigated with the X-ray powder diffraction (XRD), resistivity measurements, and Raman spectroscopy. XRD and resistivity analyses show that thermal annealing at 550 °C improves the crystalline fraction and Fe-Si grain size. Raman spectra identified hematite, goethite, magnetite, as well as graphite contamination of film surfaces.

Abstract: Surface structure and magnetic properties of thin films of the FINEMET-type alloy modificated by Mo (FeCuNbSiBMo) were studied in the aim of establishing of their dependence on heat treatment conditions. The thicknesses of the films were varied from 10 to 800 nm. Dependence of the microstructure of the films surface on the annealing temperature was analyzed using scanning probe microscopy. Parameters of the topography features were estimated as a function of the films thickness and annealing temperature. Magnetic hysteresis loops were measured using vibrating sample magnetometer and discussed in the focus of surface and thickness influences.

Abstract: The magnetic static permeability of sputtered FeCuNbSiB and electrodeposited NiFe patterns with thicknesses varying from 0.1 to 8 μm has been studied. The permeability varies proportionally with the pattern size/thickness ratio, like for uniformly magnetized patterns. Different hypothesis on this variation have been investigated and a critical analysis favors a demagnetizing effect. The comparison between experimental results and the theoretical value of the demagnetizing factor of squares plates confirms MOKE imaging, i.e. large magnetic domains but a non-uniform magnetization in the samples.

Abstract: In this research, FINEMET alloy with composition of Fe_73.5Si_13.5B₉Nb₃Cu₁ was produced by mechanical alloying from elemental powders. The effect of milling time on the magnetic and structural properties of alloy has been investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometery. The results showed that milling for 53 hr leads to the formation of Fe supersaturated solid solution which includes Si, B and Nb atoms with mean crystallite size of ~30 nm. The shift of the main peak of Fe to the higher angles indicated that Si and B atoms dissolve in the Fe solid solution, at primary stage of mechanical alloying, up to the 42 hr while Nb atoms dissolve at final stages. The magnetization of milled powder for 53 hr was 173.7 emu/g, almost the same as that of the melt-spun ribbon. In addition; the coercivity reached to 15.5 Oe after 53 hr of milling. The higher value of coercivity in mechanically alloyed samples is attributed to strains induce to the structure during milling and the lack of amorphous phase and exchange interaction between nanograins.

Abstract: The application of FINEMET-type materials with specific magnetic properties prepared by the crystallization of amorphous alloys is often limited by their brittleness. The structure of these materials consists of nanosized Fe-based grains surrounded with amorphous phase. Then the final macroscopic mechanical properties are considerably influenced by the properties of this amorphous phase. Direct creep measurements during the crystallization of FINEMET alloys were performed and the creep properties of the residual amorphous phase formed during the nanocrystallization were described. It was shown that due to relatively high temperatures the residual amorphous phase undergoes intensive structural relaxation resulting in the obvious embrittlement of these materials.

Abstract: The magnetic and structural properties of FINEMET [Fe73.5Si13.5B9Nb3Cu1 wt %] amorphous powder were investigated after nitrification and mechanical milling. Fe-based amorphous powder were nitrified and crystallized simultaneously at 550°Cusing by ammonia(NH3) gas. Nitrified powder exhibited iron nitride phase such as γ′-Fe4N, Fe3N and α″-Fe16N2. Nitrified particles were more brittle than raw particles. As a result, nanometer sized nitride powder were fabricated by high energetic ball milling method. The saturation magnetization(Ms) and coercivity(Hc) of nitrified powder were increased due to nitride phase.