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Wyświetlanie 1-15 z 81
Tytuł:
Rayleigh Region in Amorphous and Nanocrystaline FINEMET Alloy
Autorzy:
Novák, L.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/1200807.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Kj
75.50.Tt
75.60.Ch
75.60.Ej
75.60.Jk
Opis:
The magnetization processes in region of small excitation magnetic fields - Rayleigh region, were investigated on the amorphous and nanocrystalline FINEMET ribbons. The significant differences in behaviour of these materials were found. This could be explained by the difference in the value of magnetoelastic anisotropy as well as by the different thickness of the domain walls in these materials.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 126-127
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Minor Loop Scaling Rules for Finemet Type Soft Magnetic Cores
Autorzy:
Varga, L.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/1367508.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Bb
75.50.Kj
75.60.-d
75.60.Ej
Opis:
The validity of the Steinmetz law $(P=K B^{n})$ has been analyzed using the tanh model, by splitting the minor loops in three or two components, corresponding to different magnetization processes at different excitation levels. It is shown that the original Steinmetz law with the exponent n=1.6 is valid only at and above the coercive field, for intermediate and high induction values, where all the three magnetization processes are present. At small magnetization levels the exponent is about 3, much higher than the original proposed value.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 156-157
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Transition in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ Perovskite Induced by Electric Field at a Given Magnetic Field
Autorzy:
Baszyński, J.
Kowalczyk, A.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/2013719.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Et
Opis:
We report the discovery of new effect in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ - the jump of magnetization induced by external electric field E (2.5-4)V/cm at a given magnetic field H (18-25) kOe at T=4.2 K. This effect is large when compared with a metamagnetic transition induced by the magnetic field in many substances. The origin of the magnetization jump induced by external electric field has not yet been explained. We assume that this transition is induced by the hopping of E-excited e$\text{}_{g}$ electrons and that this is a source of a jumpwise increase in magnetization in the non-collinear magnetic phase within the perovskite. This effect can be attributed to a strong coupling between carriers induced by the electric field (the conduction electrons e$\text{}_{g}$), and the local magnetic moments (t$\text{}_{2g}$-localized spins) through a mechanism of the Zener double exchange.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 879-882
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exchange Bias in Iron-Oxide Particles Nanocasted in Periodic Porous Silica
Autorzy:
Zeleňáková, A.
Kováč, J.
Zeleňák, V.
Powiązania:
https://bibliotekanauki.pl/articles/1810584.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.46.Df
68.37.Lp
75.20.-g
75.30.Cr
Opis:
Iron-oxide nanoparticles were nanocasted in the periodic mesoporous silica matrix, consisting of two-dimensional hexagonally ordered channel system with the mean diameter of the channels about 7 nm. The magnetic measurements of dc magnetization confirm behavior typical of a superparamagnetic system, such as the irreversibility of the zero-field-cooled and field-cooled curves, presence of a maximum in zero-field-cooled curve related with blocking temperature $T_C$ and revealing of coercivity $H_C$ below $T_C$. The existence of negative exchange bias effect below $T_C$ was confirmed in our system represented by value of exchange bias field $H_{EB}$=-970 Oe measured at the temperature 2 K.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 357-359
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanochemical Preparation and Magnetic Properties of Fe₃O₄/ZnS Nanocomposite
Autorzy:
Bujňáková, Z.
Zorkovská, A.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/1032141.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Bc
81.20.Ev
81.20.Wk
Opis:
Powder nanocomposite of Fe₃O₄/ZnS was prepared by mechanochemical synthesis in a planetary ball mill. In this reaction natural magnetite mineral Fe₃O₄ was used, together with zinc acetate (CH₃COO)₂Zn·2H₂O and sodium sulfide Na₂S·9H₂O, as precursors for the zinc sulfide ZnS. X-ray diffraction revealed that the sample is composed of small nanocrystalline particles, containing Fe₃O₄ and ZnS. The non-milled magnetite showed distinctive Verwey transition at around 120 K, this becomes suppressed after milling, as a consequence of structural disorder and presence of defects. Moreover, the reduction of saturation magnetization from 91 A m²/kg to 69.2 A m²/kg was observed, as a consequence of the milling process. The magnetization of the Fe₃O₄/ZnS nanocomposite was the lowest (34.5 A m²/kg), due to the milling and to the decreased weight fraction of the ferrimagnetic component. Nevertheless, the Fe₃O₄/ZnS sample demonstrates ferrimagnetic behavior as well, and its structure is less perturbed by milling, the Verwey transition, although less impressive, but is preserved.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1120-1122
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Pulse Heating on Rayleigh Area of Amorphous FINEMET-Type Alloy
Autorzy:
Novák, L.
Kováč, J.
Hubač, L.
Powiązania:
https://bibliotekanauki.pl/articles/1032143.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.En
75.50.Kj
75.60.Nt
75.60.Jk
Opis:
The effect of pulse annealing on magnetization processes in FINEMET-type alloy in weak magnetic fields (the Rayleigh area) is studied in this paper. Rapidly quenched FINEMET ribbon in the original amorphous state was chosen for the study. The significant differences in behavior of studied materials are ascribed to the differences in internal mechanical stresses, which bring about the changes in total magnetic anisotropy and consequently also changes in domain walls thickness.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 753-755
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of the Magnetization Processes in Amorphous and Nanocrystalline FINEMET by the Numerical Decomposition of the Hysteresis Loops
Autorzy:
Kováč, J.
Novák, L.
Varga, L.
Powiązania:
https://bibliotekanauki.pl/articles/1032185.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.60.-d
75.60.Ej
Opis:
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.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 732-734
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
AC Magnetic Susceptibility Study of Fe and Co Based Nanoparticles
Autorzy:
Zeleňáková, A.
Kováč, J.
Zeleňák, V.
Powiązania:
https://bibliotekanauki.pl/articles/1368479.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.75.Fk
81.05.Rm
75.40.Cx
Opis:
We have investigated magnetic properties of three different samples composed of magnetic Fe or Co core and protective Au or Pt metallic shell, namely Fe@Au, Co@Au and Fe@Pt samples, with sizes of about 10 nm, 8 nm and 5 nm respectively. We have measured and analysed the experimental data of real and imaginary component of ac susceptibility through theoretical laws for non-interacting and interacting particles and we have estimated the strength of their magnetic interactions. Our analyses showed the increase of inter-particle interactions with decreasing particles size.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 222-223
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability analysis of forest machines due to FMEA method
Autorzy:
Ťavoda, P.
Kováč, J.
Łukaszczyk, Z. Ł.
Powiązania:
https://bibliotekanauki.pl/articles/409738.pdf
Data publikacji:
2018
Wydawca:
STE GROUP
Tematy:
reliability
FMEA method
forest machines
maintenance
Opis:
The article deals with the research of operational reliability of forest felling machines with the method FMEA (Failure Mode and Effect Analysis) and its implementation for observed machines in the organization. Forwarders 810D by John Deere were chosen for this research. The research was realized in real operational conditions. Application of the FMEA method allows flexibility in case of unexpected situations and optimization of human potential abilities. FMEA tool is a tool preventing outages operational reliability and preventive tool for ensuring the maintenance of facilities. This paper explores and verifies the operational reliability theory in practical real-world conditions, resulting in a reduction in operating (variable) costs, minimization of failures and readiness and increased performance of observed machines.
Źródło:
Management Systems in Production Engineering; 2018, 4 (26); 200-206
2299-0461
Pojawia się w:
Management Systems in Production Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of 1D Ordering on Magnetic Properties of Iron Nanoparticles coated by Silica Shell
Autorzy:
Zeleňáková, A.
Hrubovčák, P.
Zeleňák, V.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/1030766.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.75.Fk
68.37.Og
Opis:
Peculiar magnetic properties of 1D arranged composite consisting of Fe nanoparticles coated by insulating SiO2 layer were studied. Silica layer promotes the self-organization of 4 nm iron nanoparticles to the chain-like structures. Magnetization study shows that prepared nanoparticles exhibit very strong inter-particle magnetic interactions, which lead to long-range ordering of nanoparticles magnetic moments. Magnetic properties show superferromagnetic behaviour. The low value of room temperature coercivity, the existence of electrical insulating silica layer and small size of iron nanoparticles favour studied material for potential usage in microelectronic devices designed for high voltage signals modulated by high frequencies.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 561-563
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Mechanism of H-Induced Curie-Point Relaxation in Fe-Based Glassy Alloys
Autorzy:
Balla, S.
Kováč, J.
Novák, L.
Lovas, A.
Powiązania:
https://bibliotekanauki.pl/articles/1813523.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.23.Cq
71.55.Jv
75.50.Kj
81.40.Rs
Opis:
In Fe based glasses not solely the stress-sensitive magnetic properties, but also the amorphous Curie temperature $(T_C^{am})$ can be altered by hydrogen absorption or due to the low temperature "heat treatments" in liquid $N_2$ (-196°C). The sign and magnitude of this $T_C^{am}$ shift is strongly compositional dependent, but it is also influenced by the thermal history of glasses (heat treatments). In this paper new experimental results are presented, which were obtained on FeCrB alloys, supporting the previous observations. An attempt of interpretation of the results is also made, which is based on the existence of the quenched-in phase reminiscences, being inherited from the liquid structure.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 55-59
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Study of the Fe Coated by Au Nanoparticles
Autorzy:
Zeleňáková, A.
Kováč, J.
Kavečanský, V.
Zeleňák, V.
Powiązania:
https://bibliotekanauki.pl/articles/1813874.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.46.Df
68.37.Lp
75.20.-g
75.30.Cr
Opis:
Nanosized iron-gold magnetic nanoparticles with an average particle size 10 nm were prepared by a reverse micelle method. The magnetic properties measurements of DC and AC magnetization confirm behaviour typical of a superparamagnetic system, such as the irreversibility of the zero-field-cooled and field-cooled curves, the frequency dependence of a blocking temperature $T_B$, and revealing of coercivity H_C below blocking temperature. The quantitative analysis of AC susceptibility due to value of parameter $C_1$ = Δ$T_B$/($T_B$ Δ log f)=0.0242 confirming the existence of inter-particle interaction in our system.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 533-536
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superparamagnetism in Cobalt Nanoparticles Coated by Protective Gold Layer
Autorzy:
Hrubovčák, P.
Zeleňáková, A.
Zeleňák, V.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/1368320.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.75.Fk
68.37.Og
Opis:
In this work we present the study on structural and magnetic properties of fine cobalt nanoparticles coated by protective gold layer synthetized by microemulsion method. Structural measurements (powder XRD, HRTEM) confirmed spherical shape of the particles, their nanocrystalline character and presence of individual Co and Au phases. Investigation of magnetic properties of the particles revealed superparamagnetic behavior at higher temperatures and magnetic hysteresis at low temperatures. Average magnetic moment of individual particle $m_{p}~86.3μ_{B}$ was established. The critical temperature, below which the magnetic moments of the particles are blocked, was $T_{B}$=6 K. Investigation of magnetic relaxation processes via magnetic susceptibility, detected one maximum attributed to single relaxation process, present in the particles. Obtained data, interpreted in terms of Neél-Arrhenius and Vogel-Fulcher theoretical models, confirmed the presence of strong magnetic interparticle interactions.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 216-217
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Clean bulk YBaCuO superconductors doped by paramagnetic ions of Sm and Yb
Autorzy:
Jirsa, M.
Volochová, D.
Kováč, J.
Diko, P.
Powiązania:
https://bibliotekanauki.pl/articles/1054700.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Ha
74.25.Op
74.25.Sv
74.60.Ge
74.72.-h
Opis:
The recently developed clean cuprate technology was employed to study the effect of tiny amounts of paramagnetic Yb and Sm ions on electromagnetic properties of bulk YBaCuO. Small samples of about 1.5×1.5×0.5 mm³ were measured by vibrating sample magnetometer in the field range ±9 T and temperatures 30 K to 10 K in the non-superconducting tetragonal state and 300 K to 70 K in the orthorhombic, superconducting state. In the latter case, we observed the reversible paramagnetic moment above T_{C}, similar as in the tetragonal state. Below T_{C} an irreversible magnetic moment was observed from which critical current density, J_c, was evaluated using the extended Bean model. The effect of doping by Yb and Sm ions on J_c was studied and a correlation between J_c and the total paramagnetic moment was found. Both J_c(B) and the normalized pinning force density as a function of the reduced magnetic field were analyzed in terms of the classical model and discussed with respect to the material anisotropy, giving us at least a rough idea on the type of the effective pinning type and mechanism.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1027-1029
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Room-Temperature Ferromagnetism in Zn-Mn-O, X-Ray Photoemission Surface Study
Autorzy:
Milivojević, D.
Babić-Stojić, B.
Blanuša, J.
Kovač, J.
Powiązania:
https://bibliotekanauki.pl/articles/1503685.pdf
Data publikacji:
2011-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
81.40.Rs
81.70.Jb
82.80.Pv
Opis:
Room temperature ferromagnetic properties of Zn-Mn-O show evident dependence on manganese concentration and preparation conditions. We systematically studied series of samples with manganese concentration ranging from 0 to 10 at.%, prepared in air at thermal treatment temperatures ranging from 400 to 900°C. The samples were investigated by X-ray diffraction, TEM, magnetization measurements and XPS spectroscopy. XPS analyses of surface composition, chemical bonding and XPS depth profiling were successfully employed on powder revealing the chemical composition at the surface of the grains and underneath. The study emphasizes important role of the grain surface in observed room temperature ferromagnetism. It seems that the ferromagnetic phase is correlated with oxygen build up at the surface.
Źródło:
Acta Physica Polonica A; 2011, 120, 2; 311-315
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 81

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