Creep Behaviour of Co-Based Amorphous Alloys

The detailed study of the temperature dependence of the viscosity of (Co,Fe)-(Si,B) amorphous metallic alloys up to crystallization temperatures was carried out. The kinetics of the non-equilibrium viscosity was described using Vogel-Fulcher-Tammann law below the glass transition temperature

Time and thermal stability of magnetic properties of amorphous Fe80TM3B17 alloys

We have investigated the influence of the addition of different transition metals (Fe, Co, Cr, Mn, Mo, Ni, Os, Pt, Ru, Ta, Ti, V and W) on the time-temperature stability of amorphous Fe80TM3B17 alloys. Time stability is represented by the Magnetic After - Effect (MAE). Each element influences near neighbourhood of other atoms by its characteristic way which results in a different chracteristics of the MAE spectra and its spectra of activation energies. It turned out from our measurements that samples can be divided into the three groups : The first one contains alloys with MAE similar to that of an FeB alloy, in the second there are alloys with different MAE, and in the third one there are alloys with almost no MAE. It was found that MAE can be successfully described on the basis of the micromagnetic model with activation parameters Q* = 1.3 - 1.7 eV and τ0 = 10-18 - 10-13. Small values of the preexponential factor points out that MAE in Fe80TM3B17 amorphous alloys is caused by the rearrangement of the mobile atom pairs within the domain walls

Complex Permeability After-Effect and Analysis of Power Losses in Ferromagnetic Co-Based Amorphous Alloy

Complex permeability $(μ=μ_1-iμ_2)$ after-effect of near-zero magnetostrictive CoFeCrSiB amorphous alloy was investigated in magnetic field H (t)= $H_0$ exp ( i 2π f t) after demagnetization. For frequencies f from 200 Hz to 2000 Hz and for the small amplitude H_0 < $H_{cr}$ we observed practically constant both real $μ_1$ and imaginary part $μ_2$ of permeability. A measured small decrease in the real part $μ_1$ and increase in the imaginary part $μ_2$ with frequency f were theoretically calculated for a quadratic form of a domain wall potential $E_S$ (x)=1/2α $x^2$. The calculated loss factortan δ = $μ_2 μ_1$, which is small at amplitude $H_0$ < $H_{cr}$, corresponds to power losses due to eddy currents induced around reversibly moving domain walls

Creep Behaviour of Co-Based Amorphous Alloys

The detailed study of the temperature dependence of the viscosity of (Co, Fe)-(Si, B) amorphous metallic alloys up to crystallization temperatures was carried out. The kinetics of the non-equilibrium viscosity was described using Vogel-Fulcher-Tammann law below the glass transition temperature

Stress Dependence of the Switching Field in Glass Coated Microwires

Here we present the study of the stress dependence of the switching field in amorphous glass-coated magnetic microwire of composition FeNiMoB. Samples were heat treated in the temperature range from 250°C up to 500°C in order to obtain relaxed and nanocrystalline state. As-cast microwire shows strong stress dependence of the switching field, which decreases with the temperature of annealing. The sample is almost not stress dependent after heat treatment at 425°C, because the magnetostriction vanishes. However, the strongest stress dependence was found for the microwire annealed at 400°C, just below the optimal annealing temperature to obtain the nanocrystalline state

Directional Ordering in Amorphous Fe43Ni43Zr7Cu1B6Fe_{43}Ni_{43}Zr_7Cu_1B_6 Ferromagnetic Alloys

Development of the atomic directional ordering in the $Fe_{43}Ni_{43}Zr_7Cu_1B_6$ alloy, during its conventional the same as after transverse magnetic field annealing, was experimentally studied by the amplitude dependence of susceptibility and hysteresis loops measurements, respectively. Diffusion processes of the mobile atoms caused perminvar effect, decrease of the initial susceptibility, increase of the critical field, and linear shape of the hysteresis loop. Uniaxial magnetic anisotropy, created during magnetic field annealing of the FeNiZrCuB alloy, was confirmed also by observation of the surface domain structure

Influence of Ni-substitution on magnetic properties of annealed FeNiNbCuSiB alloys

A set of amorphous Finemet based ribbons of the composition Fe73 5-xNixNb3Cu1Si13-5B9 (0 ≤ x ≤ 25) was produced bu melt spinning technique. For determining the critical temperatures DSC studies as wel as ac-susceptibility measurements were performed. Additionally pinning field and MAE (magnetic after-effect studies were made. After a heat treatment at 550°C for 1h a nanocrystalline state was formed which leads to a magnetic softening for Ni concentrations up to x=15. The first crystallization temperature at about 545 °C is nearly independent of the Ni concentration. The second crystallization stage decreases from 695°C (for x=0) to 588°C (for x=25°C)