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    Wyświetlanie 1-13 z 13
    Tytuł:
    Magnetic and structural studies into the effect of solvent exchange process in metal-organic framework MOF-76(Gd)
    Autorzy:
    Almáši, M.
    Zeleňák, V.
    Zeleňáková, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1054760.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.30.Sg
    75.75.Fk
    65.40.gd
    Opis:
    Effect of solvent exchange/absence on magnetic and structural properties of microporous metal-organic framework MOF-76(Gd) has been performed. Three compounds have been prepared and characterized: as synthesized MOF-76(Gd)-DMF, which containing DMF (N,N'-dimethylformamide) and H₂O molecules in the cavity system, activated complex without solvents, MOF-76(Gd) and water exchanged sample MOF-76(Gd)-H₂O. The structural study showed that compounds undergo structural changes after activation/exchange processes. Changes were mainly observed in the magnetic properties and distances between Gd...Gd ions: 4.718 Å for MOF-76(Gd)-DMF, 4.326 Å for MOF-76(Gd)-H₂O and 4.296 Å for MOF-76(Gd). The magnetic properties of the samples were studied by magnetic susceptibility χ_{M}(T) and magnetization M(H). The low positive value of the Weiss constant, Θ = 1.54 K in compound MOF-76(Gd)-DMF shows on a very weak ferromagnetic interaction. On the contrary, the negative values of Θ in complexes MOF-76(Gd) (-5.58 K) and MOF-76(Gd)-H₂O (-6.23 K) confirm the existence of antiferromagnetic exchange interaction between Gd(III) ions.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 991-993
    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:
    Ordered Nanoporous Silica Modified with Nanoparticles of Lanthanide Oxides
    Autorzy:
    Zeleňáková, A.
    Kapusta, O.
    Zeleňák, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1368473.pdf
    Data publikacji:
    2014-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.75.Fk
    81.05.Rm
    75.40.Cx
    Opis:
    Lanthanide oxide nanoparticles were encapsulated inside of pores of highly ordered periodic silica of SBA15 type with hexagonal symmetry. The magnetic properties of such nanoperticles were investigated. The structural characterization using the SAXS, XANES, XRD, and $N_{2}$ adsorption measurements showed the presence of lanthanide oxides of $Ln_{2}O_{3}$ type (Ln=La, Pr, Nd, Gd, Eu), with the size of about 5 nm, incorporated in nanoporous channel system. Their magnetic properties, studied by SQUID apparatus, showed the weak antiferromagnetic ordering at 2 K in the nanocomposites $Gd_{2}O_{3}$@SBA15, $Pr_{2}O_{3}$@SBA15 and $Nd_{2}O_{3}$@SBA15. This behaviour of the nanoparticles is caused by blocking process of magnetic moments, which at 300 K exhibit the superparamagnetism, evidenced from ZFC/FC magnetization.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 1; 218-219
    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:
    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:
    Scaling analysis of the magnetocaloric effect in Co/Au nanoparticles
    Autorzy:
    Hrubovčák, P.
    Zeleňáková, A.
    Zeleňák, V.
    Franco, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1054838.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.30.Sg
    75.75.Fk
    65.40.gd
    Opis:
    The system of superparamagnetic Co/Au bimetallic nanoparticles of average diameter 7 nm was investigated with respect to its magnetocaloric properties. DC magnetic measurements revealed the presence of field dependent zero field cooled M(T) maximum (6-8 K) and significant zero field cooled/field cooled irreversibility at low temperatures in the system. Documented thermal hysteresis disallow standard magnetic entropy change calculation from isothermal M(H) data, thus we attempted to employ zero field cooled M(T) data for this purpose. Magnetic entropy change was calculated employing the Maxwell relation. In maximal field variation of 1 T relative high magnetic entropy change for nanoparticles Δ S_M ≈ 0.7 J/(kg K) at T =9 K was observed. The data collapsed onto single universal curve after proper axis rescaling.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 795-797
    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:
    Magnetocaloric effect in Gd₂O₃@SiO₂ nanocomposite
    Autorzy:
    Zeleňáková, A.
    Hrubovčák, P.
    Berkutova, A.
    Kapusta, O.
    Zeleňák, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1054708.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.30.Sg
    81.05.Rm
    75.20.Ck
    75.75.Fk
    Opis:
    Nanocomposite consisting of Gd₂O₃ nanoparticles embedded in periodical porous silica matrix was investigated with respect to its magnetocaloric properties. Series of field (up to 5 T) dependence of magnetization data were recorded in temperature range 2-52 K. The data were subsequently processed employing Maxwell relation in order to calculate magnetic entropy change (Δ S_M) of the system. Examined nanocomposite exhibited reasonably high value of Δ S_M ≈ 29 J/(kg K) at maximal field change 5 T at the temperature of 2 K which suggests that this material could be feasible for cryomagnetic refrigeration applications.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 810-812
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fe₂O₃ and Gd₂O₃ Nanoparticles Embedded in Mesoporous Silica: Magnetic Properties Comparison
    Autorzy:
    Kapusta, O.
    Zeleňáková, A.
    Hrubovčák, P.
    Girman, V.
    Zeleňák, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1031039.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.78.+s
    47.11.Kb
    75.75.Cd
    75.40.Cx
    78.20.-e
    Opis:
    Nanocomposite materials containing Fe₂O₃ and Gd₂O₃ nanoparticles with the same concentration were prepared by nanocasting method. At this procedure silica matrix serves as nanoreactor for growth of nanoparticles. Temperature and external dc field dependences of the magnetization both samples were compared. Composite containing Fe₂O₃ nanoparticles shows superparamagnetic behaviour with blocking temperature around 45 K. Otherwise, paramagnetic properties were observed for the sample with Gd₂O₃ (above 10 K). Additionally, due to free pores the silica matrix could serve as medium to increase the number of bonded water molecules. These properties together with appropriate magnetic characteristics make studied materials suitable for magnetic resonance imaging applications.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 860-862
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Magnetic Properties of Fe@Pt Nanoparticles with Core/Shell Morphology
    Autorzy:
    Zeleňáková, A.
    Zeleňák, V.
    Bednarčík, J.
    Lauda, M.
    Kováč, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535141.pdf
    Data publikacji:
    2010-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.75.Fk
    75.50.Vv
    75.40.Gb
    Opis:
    We have investigated the magnetic properties of iron nanoparticles coated by platinum shell prepared by chemical procedure. Magnetic measurements using SQUID magnetometer confirm the behaviour typical for a superparamagnetic system. From the M(H) loop at 300 K the magnetic moment of each particle $m_{P}$ ≈ $250 μ_{B}$ was calculated. The magnetic relaxation study by the in-phase χ' and out-of-phase χ" ac susceptibilities in frequency range 0.1-1000 Hz suggests the existence of two magnetic layers with different magnetic spin's dynamics and strong dipolar interactions between nanoparticles. The observed magnetic behaviour is caused by the blocking process of interacting superparamagnetic particles with magnetic iron core, diamagnetic platinum shell and spin-glass like behaviour magnetic interlayer between them.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 5; 1002-1004
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structure and Magnetic Properties of Three-Dimensional Gadolinium-Based Hybrid Framework
    Autorzy:
    Almáši, M.
    Zeleňáková, A.
    Císařová, I.
    Bednarčík, J.
    Zeleňák, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1371241.pdf
    Data publikacji:
    2014-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.75.Fk
    81.05.Rm
    75.40.Cx
    Opis:
    In the present work we have focused on the preparation and magnetic study of coordination polymer formed by Gd(III) cations as nodes and formate (HCOO¯; FOR) anions as charge compensating linkers. The prepared complex with formula ${[Gd(μ_{3}-FOR)_{3}]}_{n}$ was characterized by single-crystal X-ray diffraction, and high-energy powder X-ray diffraction. The structural study showed that complex is formed by 3D polymeric network with the shortest Gd-Gd, distances of 3.998 Å. The magnetic properties of the complex were studied by magnetic susceptibility $χ_{M}(T)$ and magnetization M(H) measurements. The results show on the weak antiferromagnetic coupling at low temperatures represented by the Weiss constant θ=-0.468 K. The value of effective magnetic moment $μ_{eff}=7.57μ_{B}$, which was estimated from the experimental data is close to the theoretical value for systems with S=7/2. Correlation between crystal structure of complexes and magnetic properties is presented.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 1; 308-309
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of Total Losses of Non-Oriented Electrical Steels
    Autorzy:
    Füzer, J.
    Birčáková, Z.
    Zeleňáková, A.
    Hrubovčák, P.
    Kollár, P.
    Predmerský, M.
    Huňady, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535263.pdf
    Data publikacji:
    2010-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.50.Bb
    75.60.-d
    Opis:
    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.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 5; 1018-1019
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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