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EN
The paper presents possibilities of hysteresis loop decomposition onto the magnetization components. The reversible and irreversible magnetization changes describe processes, which are influencing reversal magnetization in studied permanent magnets. Further, these components are used for modelling the recoil curves using modified hyperbolic T(x) model.
EN
In this work the magnetic properties of ribbons with composition of Nd_{10}Fe_{83}Zr_1B_6 obtained by using the melt-spinning method were studied. From the X-ray diffraction patterns the phase composition was determined. It was found that investigated alloy was composed of α-Fe and Nd_2Fe_{14}B phases. From the peaks broadening the grain sizes of α-Fe and Nd_2Fe_{14}B phases were estimated as equal to 20 nm and 40 nm, respectively. From the recoil curves the reversible μ_0 M_{rev} and irreversible μ_0 M_{irr} parts of magnetization and differential susceptibility χ_{rev} and χ_{irr} were determined as a function of an applied field. From these dependences it was found that the pinning of domain walls at the grain boundaries is the main magnetization reversal process. The interactions between grains were investigated by means of the δ M plot. It was stated that short range exchange interaction between grains of hard and soft phases are dominant and causes the remanence enhancement.
EN
In alloy materials, the onset of crystallization temperature (T_{x}) is treated as the threshold of structural stability. In amorphous materials, this threshold is the temperature above which heterogeneous crystalline grains begin to appear. However, in amorphous materials, frozen nuclei of the crystalline grains also come into existence during the production process. These nuclei have a strong influence on the properties of the amorphous materials. The growth of the nuclei of the crystalline grains is possible even below the crystallization temperature, and maintaining control over their size allows the application properties, for example the magnetic properties, to be controlled. In this paper, the influence of two-stage isothermal annealing (below the crystallization temperature) on the structure and magnetic properties of Fe_{61}Co_{10}Y_{8}W_{1}B_{20} alloy was investigated. Samples of the material were prepared in the form of plates, and subjected to thermal treatment at temperatures of 700 K and 770 K, for 1 and 3.5 hours, respectively.
EN
Possibility of decomposing the static hysteresis loop is demonstrated. The applied method is related with decomposition of experimentally obtained reversal magnetization curve on the reversible and irreversible components. Results are applicable in analysis of reversal magnetization processes in hard magnetic materials and for simulation of hysteresis loop using hyperbolic T(x) model.
EN
The magnetization reversal mechanism in the Nd_{16}Fe_{78}B_6 hot densified magnet, aligned by means of die-upset forging has been investigated. The magnetic parameters have been derived from major hysteresis loop. The magnetocrystalline anisotropy constants K_1 and K_2 using Sucksmith-Thompson relation modified by Ram and Gaunt have been calculated from the high field measurements up to 5 T. These data have been used to determine the theoretical value of coercivity as a function of the angle Ψ_0 between the sample easy axis and the applied magnetic field direction. The experimental value of coercivity as a function of Ψ_0 has been determined from the demagnetization curves measured for different Ψ_0 angles. It was found that the best correlation between theoretical and experimental data have been achieved for magnetization reversal mechanism controlled partially by pinning of domain walls on grain boundaries and nucleation processes.
EN
The paper presents studies of time and thermal stability of magnetic properties in Fe_{61}Co_{10}Y_{8}Nb_{1}B_{20} bulk amorphous alloys. The investigated sample was prepared by suction-casting method in the form of plate. The structure was studied using X-ray diffractometry. It was found that alloy was amorphous in the as-cast state. The magnetic properties were determined using completely automated set up for measurement of susceptibility and its disaccommodation. The disaccommodation curve was decomposed into three elementary processes, each of them was described by Gaussian distribution of relaxation times. From fit of theoretical curve the peak temperature, intensity at peak temperature, average activation energies, distribution parameter and pre-exponential factor of the Arrhenius law were determined. The obtained results indicate that the disaccommodation phenomenon in studied samples is related with directional ordering of atom pairs near the free volumes.
EN
Effects of annealing on the disaccommodation phenomenon in bulk metallic glasses (BMGs), obtained by injection-casting method have been studied. The amorphous structure has been confirmed using X-ray diffractometer. The annealing process has been performed at temperature below the crystallization temperature. For all investigated samples the disaccommodation curves have been determined. The susceptibility and its disaccommodation have been used in order to define thermal and time stability of magnetic properties. Obtained results have also been used to determine activation energies of elementary processes.
EN
The aim of this paper was to show the influence of the manufacturing method of bulk amorphous alloys on the resulting magnetization processes. Samples in the form of plates were prepared by the injection or suction of liquid alloy into a copper mould. In order to determine the type and quantity of structural defects present in the bulk amorphous alloys, the indirect method, i.e. the approach to the ferromagnetic saturation, was applied. Studies revealed the presence of conglomerates of point defects, for both alloys. These defects were pinning sites of domain walls and their number, size and type was found to have a direct impact on the coercive field. Alloy produced by the suction-casting method was found to possess the highest number of these defects, and thus a higher coercive field value.
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