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  1. 76 Acta Physica Polonica A

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1
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Effect of Fe Substitution on Structural and Magnetic Properties of NiCr₂O₄

100%
Mohanty P., Prinsloo A., Sheppard C., Roos W.
Acta Physica Polonica A
|
2018
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vol. 133
|
issue 3
574-577
EN
At room temperature, the normal oxide spinel NiCr₂O₄ is tetragonally distorted and crystallizes in the I4₁/amd space group due to cooperative Jahn-Teller ordering driven by the orbital degeneracy of tetrahedral Ni²⁺. The ferrimagnetic Curie temperature (T_{C}) for NiCr₂O₄ is 74 K. The magnetic moments of NiCr₂O₄ are composed of a ferrimagnetic (longitudinal) and an antiferromagnetic (transverse) component. Exchange interaction between the magnetic cations influences the overall magnetic properties of the compound. Present work focuses on the modification of structural and magnetic properties upon substituting Fe at Cr site in NiCr₂O₄ with the motivation of changing the magnetic exchange interaction. In order to do so, single phase Ni(Cr_{0.5}Fe_{0.5})₂O₄ samples were prepared by co-precipitation techniques, while controlling the pH of precipitation. Upon Fe substitution, crystal structure was not affected much contrary to the earlier reports. In order to determine the oxidation state of each elements X-ray photoelectron spectroscopy (XPS) was performed. T_{C} was found to increase dramatically above 300 K, confirmed both from temperature and field dependent dc-magnetization studies.
2
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Study of the Magnetization Processes in Amorphous and Nanocrystalline FINEMET by the Numerical Decomposition of the Hysteresis Loops

100%
Kováč J., Novák L., Varga L.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
732-734
EN
The magnetization processes in amorphous and nanocrystalline FINEMET ribbons were studied by the numerical decomposition of the quasi-static hysteresis loop to the contributions of the domain wall movement, the domain rotations, and the domain wall annihilation and nucleation processes following the hyperbolic T(x) model of hysteresis. The hysteresis data measured during decrease of the excitation magnetic field were used for the separation of these processes. The significant differences in behavior of these two materials were found. In amorphous state the domain rotations component dominates whereas in nanocrystalline state the domain wall movement component prevails. These differences are reflected in the anisotropy field distributions as well.
3
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The Rare-earth Based Single-ion Magnet CsNd(MoO_{4})_{2}

100%
Tkáč V., Tibenská K., Orendáčová A., Orendáč M., Anders A., Pavlík V., Feher A.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
244-245
EN
Specific heat, magnetization and DC susceptibility of the single crystal CsNd(MoO_{4})_{2},a layered rare-earth dimolybdate, have been investigated nominally, in the temperature range from 100 mK to 300 K in the magnetic field up to 5 T, applied along the a axis. The analysis of the experimental data revealed the absence of a phase transition to the magnetic ordered state down to 100 mK. The application of a standard two-level model yielded an excellent agreement with the specific heat data above 2 K in nonzero magnetic field indicating a weakness of magnetic correlations and a predominant occupation of the ground-energy doublet. The latter indicates a large energy separation between the ground and first excited doublet. These measurements suggest that CsNd(MoO_{4})_{2} can represent a good realization of a single-ion magnet.
4
Publication available in full text mode
Content available

On Magnetization Reversal in Hard Magnetic Sm-Fe-N Permanent Magnets

100%
Pawlik P., Wysłocki J., Baran M.
Acta Physica Polonica A
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2001
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vol. 100
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issue 6
905-913
EN
The investigations were carried out on Sm-Fe-N permanent magnets produced by reactive diffusion method. The magnets consist of hard magnetic phases: Sm_2Fe_{17}N_{0.86} and SmFe_5 and soft magneticα-Fe phase. From the comparison of experimentally determined angular dependence of coercive field with appropriate theoretical predictions and from the dependence of coercive field on the external magnetic field determined from the minor hysteresis loops, it was stated that magnetization reversal process in Sm-Fe-N magnets is controlled by the nucleation of reversed domains process.
5
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On Temperature Dependence of Domain Structure in Cobalt

100%
Szmaja W., Polański K., Dolecki K.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
469-472
EN
The type-I magnetic contrast in a scanning electron microscope is used to study the domain behaviour on the basal planes of cobalt monocrystals of different thicknesses during a heating cycle. Digital image processing is applied to the original scanning electron microscope images for their restoration, enhancement and analysis. The main reasons for the application of digital image processing are: low level of type-I magnetic contrast, particularly used at the higher temperatures, and the complex character of the magnetic domain structure. The changes in both domain structures and type-I magnetic contrast are due to the strong temperature dependence of magnetocrystalline anisotropy energy for the hcp phase of cobalt, which implies the rotation of magnetic easy axis from the c-axis to the basal plane. The temperature of the magnetic phase transition between an open-flux and a closed-flux domain configuration was found to be dependent on the specimen thickness. The changes in domain structure during the heating cycle were reversible under the condition that the specimen was not carried through the hcp-to-fcc phase transition. Otherwise, they were partially or completely irreversible and were caused by crystal imperfections originating from the transition. The paper shows the great advantage of using digital image processing system for data restoration, enhancement and analysis.
6
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Jiles-Atherton Magnetic Hysteresis Parameters Identification

100%
Pop N., Caltun O.
Acta Physica Polonica A
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2011
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vol. 120
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issue 3
491-496
EN
This paper presents a method of fitting the magnetic hysteresis curves using a calculating algorithm within a computer programme. The calculating programme uses the equations of the Jiles-Atherton model to simulate the M(H) magnetization curve. The aim of this program is to find the values of the parameters which are part of the Jiles-Atherton model once the regression curve for a major magnetization curve obtained experimentally is found. The values of these parameters can be increased or decreased gradually. The parameters modification takes place in such a way that the root mean square deviation between the points of the two graphs, also experimentally simulated, should decrease gradually and, in the end, it should be found below the preestablished percentage value in comparison to the previous value. The procedure for minimizing the root mean square deviation has as a result the fact that the simulated curve represents the regression curve. The calculating programme considers a second method of calculating the values of the parameters by using the already found regression curve. This paper also presents the values of the Jiles-Atherton model parameters obtained by fitting the magnetization curves of several cobalt ferrites samples, sintered at different temperatures.
7
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A Comparison of Different Estimation Methods for Hysteresis Modelling

100%
Jastrzębski R., Chwastek K., Biondić I., Miličević K.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1228-1231
EN
The paper focuses on the estimation techniques for a low-dimensional phenomenological model of ferromagnetic hysteresis proposed by the Brazilian research group GRUCAD. The description is expressed with an ordinary differential equation and some auxiliary relationships. It describes both irreversible and reversible magnetization processes and addresses some problems inherent in the well-known Jiles-Atherton model. It is found that the differential evolution method is the most competitive technique for recovery of optimal model parameters.
8
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Correlation between Barkhausen Noise and Coercivity in Amorphous and Nanocrystalline Fe-Cu-Nb-Si-B Alloys

100%
Małkiński L., Kulik T.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
435-438
EN
Samples of amorphous and nanocrystalline alloys were prepared by proper annealing of the metallic glasses: Fe_{73.5}Cu_{1}Nb_{3}Si_{13.5}B_{9} and Fe_{73.5}Cu_{1}Nb_{3}Si _{17.5}B_{5}. Magnetic hardening of the alloys at the onset of crystallization was studied by the two independent techniques, i.e. measurements of the magnetization hysteresis loops and Barkhausen effect. A good correlation between the coercivity and the maximum power of the Barkhausen noise has been found in these two compositions of the alloys.
9
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Magnetization Study of the AFM-FM Coexistence in the Manganite System Pr_{0.5}Ca_{0.5-x}Sr_xMnO_3

100%
Maryško M., Jirák Z.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
143-146
EN
For the manganites Pr_{0.5}Ca_{0.5-x}Sr_xMnO_3 (x=0;0.3) the temperature and cooling field dependence of the reduced remanence asymmetry indicates the antiferromagnetic exchange between the antiferromagnetic and ferromagnetic spins at the surface of the clusters. For x=0.3 we deduce the radius of the cluster in the field cooled regime to be about 20 times larger than that for x=0.
10
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Separation of Magnetization Loop in Domain Wall Movement and Domain Rotation Contributions for Soft Magnetic Materials

100%
Varga L., Kovács G.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
159-162
EN
The domain wall movement and magnetization rotations processes are separated experimentally in quasi-static magnetization process of a Finemet type ultrasoft magnetic material. The reversible domain rotations contribution is obtained from the integration of the reversible permeability, μ_{DR}, as a function of biasing DC field, measured with very small alternative field amplitude, less than 0.05H_c. The domain wall movement component is obtained by the integration of the permeability obtained by extraction of μ_{DR} from the differential permeability derived from one branch of the quasi-static major loop.
11
Publication available in full text mode
Content available

Mechanism of Rotational Hysteresis Energy in Sm-Fe-N Permanent Magnets

100%
Pawlik P., Wysłocki J., Dziliński K.
Acta Physica Polonica A
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2002
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vol. 101
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issue 2
267-277
EN
Investigations were carried out on Sm-Fe-N permanent magnet produced by the reactive diffusion method with different grain sizes (from 8.6 to 0.97μm). The rotational hysteresis energy has been measured as a function of the applied field. The proposed model of rotational hysteresis energy is in good agreement with the experimental results. It is shown that the magnetization reversal process in Sm-Fe-N magnet is controlled by the nucleation of reversed domains.
12
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Magnetic Fluxgate Sensor Characteristics Modeling Using Extended Preisach Model

100%
Frydrych P., Szewczyk R., Salach J.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
18-19
EN
This paper presents the implementation of the extended Preisach model for fluxgate sensor characteristics modeling. The developed model enables the optimization of fluxgate sensor parameters for a given core material. Model consists of two parts. The first one describes magnetic characteristics of the core, while the second part calculates output signal according to sensor dimensions and electric circuit parameters. The model is easy to adapt for modeling of other devices with magnetic cores. It can be used instead of costly and time consuming prototype testing.
13
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Magnetic Tailoring of Domains in NiFe/Au/Co/Au Multilayers by He Ion Bombardment through Nanospheres

100%
Glapka W., Kuświk P., Sveklo I., Urbaniak M., Jóźwiak K., Weis T., Engel D., Ehresmann A., Błaszyk M., Szymański B., Maziewski A., Stobiecki F.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
348-351
EN
Sputter deposited (Ni_{80}Fe_{20}/Au/Co/Au)_{10} multilayers, characterized by alternating in-plane and perpendicular anisotropies of the NiFe and Co layers, respectively, and out-of-plane stripe (labyrinth) domain structure in the Co layers, were bombarded by He^+-ions (10 keV) through a mask consisting of polystyrene nanospheres with a diameter of 470 nm. The changes of multilayers magnetic properties after ion bombardment are correlated with the used mask structure.
14
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Investigation of Total Losses of Non-Oriented Electrical Steels

100%
Füzer J., Birčáková Z., Zeleňáková A., Hrubovčák P., Kollár P., Predmerský M., Huňady J.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
1018-1019
EN
The aim of this work was to investigate the influence of microstructural features on the soft magnetic properties. The materials chosen for this work were two types of the Epstein strips of commercially produced non-oriented electrical steels by U.S. Steel Košice. The AC magnetic properties in 0.2-100 Hz frequency range were obtained by measurements of AC hysteresis loops by a fluxmeter based non-standard single sheet AC hysteresisgraph. The influence of the grain size and magnetic domains structure on the partial contributions (hysteresis, eddy current and anomalous) to the total losses is also discussed. The results of the frequency dependence of the total losses, measured by a single sheet loop tracer along the rolling direction and perpendicular to the rolling direction, show different contribution of partial components.
15
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Magnetic Studies of EuBa₂Cu_{3-x}RuₓO_{7-δ} Compounds

80%
Dvurečenskij A., Cigáň A., Bystrický R., Škrátek M., Billik P., Majerová M., Maňka J.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
300-302
EN
Effects of Ru addition on magnetic properties of EuBa₂Cu_{3-x}RuₓO_{7-δ} compounds were studied. Samples of EuBa₂Cu_{3-x}RuₓO_{7-δ} with x from 0.00 to 0.70 were prepared by the solid state reaction technique from Eu₂O₃, BaCO₃, CuO and RuO₂ precursors. Temperature dependences of the zero-field cooled (ZFC) and the field cooled (FC) DC magnetic moment at low and high applied magnetic field Hₐ were measured by the QD SQUID magnetometer MPMS XL-7 and AC magnetization M_{AC}(H) curves at 77 K by the compensation method using the second-order SQUID gradiometer. The molar susceptibility χ of the samples was corrected to the effects of the sample holder and diamagnetism and χ* also was corrected to the temperature independent paramagnetic/diamagnetic contribution χ^{TN} and fitted by the Curie-Weiss relation. The values of the Weiss temperature and the effective magnetic moment have been estimated at low and high value of applied magnetic field.
16
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The Effect of Residual Stresses on the Coercive Field Strength of Drawn Wires

80%
Suliga M., Kruzel R., Chwastek K., Jakubas A., Pawlik P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1114-1116
EN
Residual stresses occurring in drawn wires due to technological process affect their quality, which in turn may have a substantial impact on safety of use and "life" of ready-made products. Measurements of magnetic properties of the wires like coercive field strength may be useful for monitoring the level of residual stresses. The present paper examines the relationship between the drawing speed and the coercive field strength in high carbon wires. It has been found that for drawing speeds not exceeding 20 m/s the coercive field strength is proportional to residual stresses on wire surface.
17
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Magnetic Properties of SMC Cores Produced at a Low Compacting Temperature

80%
Jakubas A., Gębara P., Seme S., Gnatowski A., Chwastek K.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1289-1293
EN
Soft magnetic composites are readily used in the design of electromagnetic converters and electrical machines. In the paper, the magnetic properties of "home-made" cores made of iron powder and suspense polyvinyl chloride are examined. Samples were prepared by hot pressing of a PVC/Fe powder mixture with a different ratio of constituent components. Phase composition was investigated using an X-ray diffractometer and the presence of α-Fe was detected. Measurements of magnetic permeability revealed its allometric decrease with an increase of PVC content in composite. For the description of magnetization curves the phenomenological Jiles-Atherton model is used. The results of simulations are in a qualitative agreement with experiment.
18
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Application of Extended Jiles-Atherton Model for Modelling the Influence of Stresses on Magnetic Characteristics of the Construction Steel

80%
Jackiewicz D., Szewczyk R., Salach J., Bieńkowski A.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
392-393
EN
Paper presents the possibility of application of the Jiles-Atherton extended model to describe the magnetic characteristics of construction steel C45 under the influence of tensile stresses. Experiment was performed on the frame-shaped samples. Then, the influence of stresses on hysteresis loops was modelled with the Jiles-Atherton extended model. The obtained results of the modelling are consistent with results of the experimental measurements. The results of modelling create new possibilities of explanation of the physical phenomena connected with magnetisation of the magnetic materials under stresses, which is esential for the assessment of the state of the construction steel during its exploitation in industrial conditions.
19
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Accents in Modern High Saturation Nanocrystalline Fe-Rich Alloys

80%
Butvinová B., Butvin P., Maťko I., Janičkovič D., Kuzminski M., Ślawska-Waniewska A., Švec P., Chromčíková M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
711-713
EN
Post processing limits for iron-rich Fe-Cu-Si-B-P high-induction rapidly-quenched ribbons have been tested. 530°C/20 min is already too much, formed borides being the essential culprit of magnetic properties deterioration. Unlike standard Si-poor Fe-Nb-Cu-B-Si Finemets, these alloys annealed even in "technical" Ar below the upper limit do not create significant squeezing surfaces.
20
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Optimization of Soft Magnetic Properties in Fe₈₂Nb₂B₁₄RE₂ (RE = Y, Gd, Tb and Dy) Group of Amorphous Alloys

80%
Chrobak A., Haneczok G., Zivotsky O., Hendrych A., Kansy J., Kotur B.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
916-919
EN
Enhancement of soft magnetic properties in the selected group of amorphous alloys was examined by different experimental methods. It was shown that permeability for annealed samples (at T_{a} for 1 h; 300 K < T_{a} < 900 K) plotted vs. T_{a} shows a maximum at which is 700, 725, 725, and 750 K for Fe₈₂Nb₂B₁₄Y₂, Fe₈₂Nb₂B₁₄Gd₂, Fe₈₂Nb₂B₁₄Tb₂ and Fe₈₂Nb₂B₁₄Dy₂ alloy, respectively. For samples after the optimization annealing permeability is at least 10 times higher than in the as-quenched state. The optimized microstructure is free of iron nanograins and corresponds to so-called relaxed amorphous phase.
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