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1
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Development of Magnetic Properties during Annealing of Hf₂Co₁₁B Amorphous Alloy

100%
Musiał A., Śniadecki Z., Idzikowski B.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
786-788
EN
Influence of heat treatment on magnetic properties of amorphous Hf₂Co₁₁B alloy was investigated. Hard magnetic phase, characterized by high magnetic anisotropy, appears during crystallization. The highest coercive field equal to 1.86 kOe, was obtained for sample annealed in third crystallization stage. Longer heat treatment at T_{a} = 650°C leads to decrease in coercive field, which can be the result of excess of the HfCo₃B₂ phase volume fraction and additionally eutectoid transformation of hard magnetic phase into soft magnetic Co₂₃B₆ and fcc-Co. Decrease of volume fraction of hard phase is confirmed by the remanence ratio m_{r}. Value of m_{r}, for T_{a} = 650°C, is decreasing with annealing time from 0.4 to 0.27 for 30 min and 120 min, respectively. The magnetocrystalline anisotropy constant K₁ increases from 2.23 Merg/cm³ for the amorphous ribbon to 15.84 Merg/cm³ for the sample annealed at 650°C for 30 min.
2
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Crystallisation of Amorphous Y rm_{50}Cu_{42}Al_8 Alloy

100%
Idzikowski B., Śniadecki Z., Mielniczuk B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
147-149
EN
Amorphous Y_{50}Cu_{42}Al_8 ribbon was prepared by melt-spinning technique on the Cu wheel. The crystallisation process was analysed by differential scanning calorimetry and X-ray diffraction. Differential scanning calorimetry curves characterising two crystallisation stages of Y_{50}Cu_{42}Al_8 alloy were measured in non-isothermal dynamic mode at different heating rates. Activation energies of both steps of crystallisation process were acquired by the Kissinger method and are equal to 570± 56 and 290±29 kJ/mol for the first and second stage, respectively. By annealing the ribbon at a given temperature for various times the nanocrystalline phase grains of the sizes of about 40 nm in diameter were created. The influence of the annealing temperature on the grain size evolution was also examined.
3
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Semi-Empirical Modelling of Glass Forming Ranges for Y-Co-Si System

100%
Śniadecki Z., Narojczyk J., Idzikowski B.
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vol. 126
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issue 1
62-63
EN
Glass forming abilities of a ternary Y-Co-Si system were determined on the basis of combined semi-empirical Miedema's and geometric models. The enthalpy of amorphous and solid solution phases formation, along with the mismatch entropy and GFA parameter, were analysed to indicate compositions with the highest ability for the amorphization. The large atomic radii difference between constituents, especially Y and Si, is the deciding factor of GFA. Compositions ranged between Y_{33}Si_{67} and Y_{45}Si_{55} are the best glass formers.
4
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Activation Energies of Crystallization in Amorphous RMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} (R = La, Y, Dy) Alloys

100%
Śniadecki Z., Rößler U., Idzikowski B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
409-412
EN
The effective activation energies, characteristic crystallization temperatures and enthalpies of amorphous RMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} (R = Y, La, Dy) alloys produced using melt-spinning technique were investigated by differential scanning calorimetry. X-ray diffraction measurements were performed for as-quenched and annealed samples. The crystalline structure of annealed YMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} and DyMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} alloys was determined as orthorhombic TbFe_6Sn_6-type with Cmcm (63) space group. The alloy with Y appears as a more useful non-magnetic analogue for DyMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} than the La-based alloy. The differential scanning calorimetry curves for Dy- and Y-based alloys also exhibit similar thermal behavior. The effective activation energies E_a were determined using the Kissinger approach and high values up to 778±74 kJ/mol for La-based sample were established. The comparison of Y-, La-, and Dy-based alloys suggests improvement of thermal stability with the increase in rare-earth element atomic radius in the glassy RMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} systems.
5
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Crystallization Processes of R_{4.5}Fe_{77}B_{18.5} (R = Pr, Nd) Amorphous Alloys

100%
Musiał A., Śniadecki Z., Pagnani D., Idzikowski B.
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vol. 126
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issue 1
316-317
EN
The amorphous alloys R_{4.5}Fe_{77}B_{18.5} (R=Pr, Nd) were prepared by melt-spinning technique under argon atmosphere on a cooper wheel rotating with surface velocity of 25 m·s^{-1}. The ribbons have been investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Temperatures of crystallization for Pr_{4.5}Fe_{77}B_{18.5}, measured at the heating rate 20 K/min, are equal T_{x1}=591°C for the first exothermic effect and T_{x2}=603°C for the second one (for Nd_{4.5}Fe_{77}B_{18.5} T_{x1}=594°C and T_{x2}=633°C). In the amorphous ribbons the crystallization of Fe_{3}B phase in the first step, followed by the crystallization of Pr_{2}Fe_{23}B_{3} and Nd_{2}Fe_{23}B_{3}, was observed. Both later phases appear in the process of recrystallization, immediately after Fe_{3}B formation.
6
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Critical Behavior near the Ferromagnetic to Paramagnetic Phase Transition in Y₈Co₆₂B₃₀ Amorphous Alloy

100%
Śniadecki Z., Marcin J., Idzikowski B.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
967-969
EN
The Y₈Co₆₂B₃₀ amorphous alloy is a collinear ferromagnet. The Arrott plot, the Kouvel-Fisher method, critical isotherm analysis and magnetic field dependence of maximum magnetic entropy changes were the main analytical tools used to determine the nature of the ferromagnetic/paramagnetic phase transition. Values of critical exponents (β, γ, and δ) were calculated and were convergent with those characteristic for mean-field model. It suggests that long range ferromagnetic interactions are playing main role in investigated alloy and the phase transition was confirmed to be of a second order according to the Banerjee criterion.
7
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Current-Voltage Characteristics of Nanowires Formed at the Co-Ge_{99.99}Ga_{0.01} Interface

88%
Wawrzyniak M., Maćkowski M., Śniadecki Z., Idzikowski B., Martinek J.
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issue 2
375-378
EN
We present a method of measurement of the current-voltage (I-V) and conductance-voltage (G-V) characteristics of nanowires with quantum point contact formed at the Co-Ge_{99.99}Ga_{0.01} interface. The effect of the Fermi level pinning leads to the formation of an ohmic contact between Co and Ge_{99.99}Ga_{0.01}. On the measured characteristics, above the threshold value of voltage an exponential current growth is observed. Such effect could be useful in the production of the electronic nanodevices.
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