Search results

1

Slow Relaxation of Resistance in Manganite Perovskite Nanoconstrictions

100%

Baszyński J.

Acta Physica Polonica A

|

2009

|

vol. 115

|

issue 1

339-341

EN

The time decay of the surface resistance R_{S}(t) was measured for the La_{0.7}Sr_{0.3}MnO_{3} perovskite nanocontacts obtained by break technique at liquid nitrogen. The corresponding time relaxation can be described by two-term formula: stretched exponential function and logarithmic dependence. The characteristic times τ_{1} and τ_{2} of the relaxation processes are of order of seconds and few tens of seconds, respectively. The appearance of both contributions evidences the existence of two sources of relaxation, which can be assigned to inhomogeneous changes of the angle between the magnetic moments of the neighboring Mn ions inside spin blocks (τ_{1}) and between the spin blocks (τ_{2}) occurring near surface of the nano-electrodes. Similar to magnetic viscosity, the dependence of resistance viscosity S_{R} on basis current is characterized by bell-shaped curve. These results point out the important role of the structural arrangements of the Mn-ions into spin blocks on the surfaces electrodes of the nanocontact.

2

Perminvar Effect in Amorphous Hitperm Alloy

100%

Varga M., Varga R., Vojtanik P., Komova E.

Acta Physica Polonica A

|

2008

|

vol. 113

|

issue 1

119-122

EN

Influence of the directional ordering on magnetization processes in the amorphous Fe_{44.5}Co_{44.5}Zr_7B_4 alloy was investigated in the temperature region of 27 to 300°C for stabilization times of up to 1000 min by means of the Perminvar effect. The time-temperature dependent Perminvar effect was found to be very sensitive on the stage of the domain structure stabilization. The Perminvar critical fields H_{CR} were shifted to higher values with increasing stabilization temperatures and times. At lower temperatures, the susceptibility increases over wide range of the measuring fields. Stabilization at higher temperatures causes that the susceptibility abruptly increases in the narrow field range. The record critical field H_{CR} =246 Am^{-1} was obtained.

3

Magnetic Susceptibility Disaccommodation and Mössbauer Effect in Microcrystalline Fe-Si Ribbons

100%

Ciurzyńska W.

Acta Physica Polonica A

|

2000

|

vol. 97

|

issue 4

719-728

EN

The magnetic susceptibility disaccommodation of the microcrystalline Fe-xSi (x=3, 5, 6.5, and 7.2 wt%) ribbons in the as-quenched state and after annealing at 1370 K for 1 h was investigated in the temperature range from 220 to 410 K. Simultaneously, the microstructure of those samples was studied using the Mössbauer spectroscopy. It is found that the isochronal disaccommodation curves may be decomposed into five elementary processes. Taking into account the results obtained from the Mössbauer spectra analysis, the relaxational process with activation energy equal to 0.84 eV may be considered as the Snoek relaxation. However, the relaxational processes of higher activation energy seem to be connected with jumps of C atoms in the vicinity of Fe atoms surrounded by 1, 2, 3, and 4 silicon atoms.

4

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

80%

Kravčák J., Varga R., Vojtaník P.

Acta Physica Polonica A

|

2008

|

vol. 113

|

issue 1

43-46

EN

Complex permeability (μ=μ_1-iμ_2) after-effect of near-zero magnetostrictive CoFeCrSiB amorphous alloy was investigated in magnetic field H (t)= H_0exp ( 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 realμ_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_2μ_1, which is small at amplitude H_0 < H_{cr}, corresponds to power losses due to eddy currents induced around reversibly moving domain walls.

5

Low Field Magnetic Properties of FeCo-Based Alloys

80%

Hasiak M., Miglierini M., Łukiewska A., Kaleta J., Zbroszczyk J.

|

vol. 126

|

issue 1

118-119

EN

Low field magnetic properties of amorphous (Fe_{x}Co_{1})_{76}Mo_{8}Cu_{1}B_{15} alloys (x=3, 6 and 9) were characterized by magnetic after-effect and initial magnetic susceptibility. Activation energies and pre-exponential factors of the Arrhenius law that were derived from the disaccommodation curves are of about 1.188 eV and 10^{-15} s, respectively. Local magnetic arrangement was investigated by ^{57}Fe Mössbauer spectrometry. The average hyperfine magnetic field decreases with increasing Fe/Co ratio due to smaller relative contribution of cobalt. The overall magnetic parameters of the alloy prove its good soft magnetic properties with an application potential.

6

Time and Thermal Stability of Magnetic Properties in Fe_{61}Co_{10}Y_{8}Nb_{1}B_{20} Bulk Amorphous Alloys

80%

Błoch K., Nabiałek M., Pietrusiewicz P., Gondro J., Dośpiał M., Szota M., Gruszka K.

|

vol. 126

|

issue 1

108-109

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.

7

Magnetic Relaxations in Amorphous Fe_{61}Co_{10}Y_{8}Zr_{1}B_{20} Alloy

80%

Pietrusiewicz P., Błoch K., Gondro J., Nabiałek M., Dośpiał M., Szota M.

|

vol. 126

|

issue 1

106-107

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.

8

Temperature Dependence of Magnetization Reversal of Thin Manganite Film

61%

Uspenskaya L., Nurgaliev T., Miteva S.

|

issue 1

207-210

EN

The magnetic domain structure, its transformation with temperature, and the magnetization reversal in 20 nm La_{0.7}Sr_{0.3}MnO_{3} film grown on LaAlO_{3} substrate by off-axis magnetron sputtering at 700°C and post-annealed at 600°C were studied in a wide temperature range. The magnetic domains with either in-plane- or out-of-plane-orientation of the vector of spontaneous magnetization were observed in the same film depending on the prehistory. The domains with the in-plane magnetization were found to be more stable. Magnetization reversal of the film was shown to occur via the nucleation and motion of 180-degree head-to-head domain walls, the number and the type of which were found to be dependent on temperature. Moreover, the transition between two magnetization reversal regimes was found at 30 K.

9

Influence of 1% Addition of Nb and W on the Relaxation Process in Classical Fe-Based Amorphous Alloys

51%

Pietrusiewicz P., Błoch K., Nabiałek M., Walters S.

Acta Physica Polonica A

|

2015

|

vol. 127

|

issue 2

397-399

EN

This paper features investigations into the influence of small additions of alloying elements on: structure, as well as the temporal and thermal stability of magnetic properties, and the disaccommodation effect, for the following amorphous alloys: Fe₆₁Co₁₀Y₈Me₁B₂₀ (where Me = Nb, W). The structure of the investigated samples has been confirmed by the Mössbauer spectroscopy. The obtained results indicate a strong correlation between the structure and the disaccommodation of the studied alloys. The Mössbauer studies reveal different configurations of atoms in the amorphous alloy samples, and the results indicate various potential barriers between orientations of atom pairs. For this reason, to describe the disaccommodation effect, the distribution of activation energy should be taken into account. The distribution of activation energy has been related to the distribution of relaxation times.

Refine search results

Slow Relaxation of Resistance in Manganite Perovskite Nanoconstrictions

Perminvar Effect in Amorphous Hitperm Alloy

Magnetic Susceptibility Disaccommodation and Mössbauer Effect in Microcrystalline Fe-Si Ribbons

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

Low Field Magnetic Properties of FeCo-Based Alloys

Time and Thermal Stability of Magnetic Properties in Fe_{61}Co_{10}Y_{8}Nb_{1}B_{20} Bulk Amorphous Alloys

Magnetic Relaxations in Amorphous Fe_{61}Co_{10}Y_{8}Zr_{1}B_{20} Alloy

Temperature Dependence of Magnetization Reversal of Thin Manganite Film

Influence of 1% Addition of Nb and W on the Relaxation Process in Classical Fe-Based Amorphous Alloys