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1
Content available remote CdO-Fe3O4 nanocomposite with enhanced magnetic and photocatalytic properties
Nallendran R., Selvan G., Balu A. R.
Materials Science Poland
|
2019
|
Vol. 37, No. 1
100--107
EN
Pure CdO nanopowder and CdO-Fe3O4 nanocomposite were synthesized by a cost effective chemical method, and the samples were characterized by XRD, SEM, TEM, FT-IR, UV-Vis-NIR and PL. Also, magnetic and photocatalytic properties of the synthesized samples were studied. XRD patterns of the composite confirm the presence of diffraction peaks related to both CdO and Fe3O4. EDX spectrum confirms the presence of the elements Cd, O and Fe in the composite. Peaks related to Cd–O and Fe–O bonds were observed respectively at 688 cm−1 and 592 cm−1 in the FT-IR spectrum. The paramagnetic behavior of pure CdO becomes ferromagnetic when coupled with Fe3O4. The composite exhibited a high photodegradation efficiency of 92.85 % against the degradation of methylene blue dye under visible light radiation.
2
Content available remote First-principles study of mechanical, vibrational and thermodynamic properties of magnetic XC compounds (X = Rb, Sr)
Lakdja A., Benzaidi I., Sayede A., Chahed A.
Materials Science Poland
|
2017
|
Vol. 35, No. 3
463--469
EN
Lattice dynamic and mechanical properties of hypothetical RbC and SrC compounds were investigated using the ab-initio pseudopotential method and a linear response scheme. The lattice dynamics was studied in the framework of the density functional perturbation theory (DFPT). The dynamical and mechanical stability of the hypothetical RbC and SrC compounds was proved in their equilibrium B1 structure. In addition, the same stability was confirmed in the B3 phase. The thermodynamic properties were also investigated. They exhibited the same trend in both phases, and followed the Debye model. These results were confirmed in the ferromagnetic state, which makes the investigated compounds promising candidates in the spintronic field.
3
Content available remote Magnetic properties of La0.7Sr0.3Mn0.85Nb0.15-xMgxO3 system
Troyanchuk I., Tereshko N., Bushinsky M., Fedotova V., Partyka J.
Przegląd Elektrotechniczny
|
2016
|
R. 92, nr 1
148--150
EN
Structural and magnetization measurements have been performed on the La0.7Sr0.3Mn0.85Nb5+ 0.15-xMg2+ xO3 system. With rise of the Mg2+ content the formal oxidation state manganese increases from +3 (x=0) up to +3.55 (x=0.15). The substitution of Nb5+ with Mg2+ leads to a gradual weakening of the ferromagnetic component while in the x=0.15 compound A-type antiferromagnetic short-range order is stabilized in spite of macroscopic R-3c symmetry. It is suggested that ferromagnetism is originated from superexchange interactions via oxygen.
PL
Przeprowadzono pomiary strukturalne i namagnesowania układu La0.7Sr0.3Mn0.85Nb5+ 0.15-xMg2+ xO3.Wraz ze wzrostem zawartości Mg2+formalny stopień utlenienia manganu wzrasta z +3 (x=0) aż do +3.55 (x=0.15). Zastąpienie Nb5+ poprzez Mg2+prowadzi do stopniowego osłabienia składnika ferromagnetycznego podczas gdy w związku x=0.15 typu A antyferromagnetyczny porządek krótkiego zasięgu jest ustabilizowany pomimo makroskopowej symetrii R-3c. Sugeruje się, że ferromagnetyzm pochodzi z nadwymiany za pomocą tlenu.
4
Content available remote Wpływ substytucji kationowej na strukturalne i magnetyczne właściwości wybranych chromitów selenowych
Jendrzejewska I.
Wiadomości Chemiczne
|
2010
|
[Z] 64, 9-10
859-898
EN
Selenospinels with general formula ACr2Se4 (A = Zn, Cu, Cd) were doped with nickel and tin ions. The chemical synthesis was carried out based on solid phase reactions. To estimate the chemical composition of the mono- and polycrystalline compounds, the following methods were applied: JEOL scanning microscope and ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectrometry). For the obtained polycrystalline compounds, their structural parameters were defined using X-ray diffraction analysis and Rietveld method. Definition of structure of the monocrystals was carried out using KM4 four-circle diffractometer and SHELX software. Magnetic properties were investigated with strong stationary magnetic fields up to 14 T in the temperature range of 4.2-300 K using an induction magnetometer and with stationary magnetic fields up to 0.5 T in the temperature range of 1.8-300 K using a SQUID superconducting magnetometer. In the systems doped with nickel, depending on the reaction stoichiometry, nickel ions were directed to tetrahedral or octahedral positions. When the octahedral positions are fully occupied by chromium ions, small amounts of nickel directed to tetrahedral positions are able to occupy them. The increasing amount of Ni2- ions tends to occupy the octahedral positions in accordance with preference energy, leading to change in structure from cubic to monoclinic one [19, 37, 38]. Nickel ions present in the spinel crystal lattice influence the magnetic properties of these compounds. For ZnCr2-xNixSe4 system, an increase in values of effective magnetic moment and saturation magnetic moment accompanying the increase in nickel ions concentration was ascertained. It was caused by the presence of another magnetic ions in ZnCr2Se4 crystal lattice. The values of paramagnetic Curie-Weiss point and Néel point decrease with the increase in nickel concentration. It is associated with an increase in antiferromagnetic interactions in the system caused by nickel ions [39-41]. Like in the Cd1–xNixCr2Se4system, saturation magnetic moment does not depend on the amount of nickel built-in, and the crystals exhibit strong ferromagnetic interactions. Lack of a change in saturation indicates that nickel is built in with compensated magnetic moment, or in a low-spin state (S = 0). Cadmium and nickel ions occupy tetrahedral positions and chromium ions - octahedral ones [42]. In the systems doped with tin, the reactions carried out in the solid phase were aimed to build in tin ions in tetra-and octahedral positions. X-ray diffraction studies confirmed the presence of tin ions in selected chromites. Mössbauer spectroscopy applied for the complex system Zn1–xSnxCr2Se4 confirmed the presence of tin ions in two inequivalent positions: in tetrahedral and in octahedral environments. Based on theses considerations, the general formula of these compounds may be as follows: ZnxSnδCrySnηSe4, where δ – parameter describing the share of tin ions in tetrahedral sublattice, η – parameter describing the share of tin ions in octahedral sublattice [43]. Although tin ions does not contribute to a magnetic share, their presence in the crystal lattice promotes an increase in antiferromagnetic interactions in the studied compounds. Under the influence of tin ions, conductance changes from p-type (hole conduction) occurring in pure ZnCr2Se4to n-type (electron conduction) [44, 45]. In CuCr2-xSnxSe4 system, magnetic properties change from ferromagnetic for nominal value x = 0.2 to antiferromagnetic for nominal value x = 1.0. These changes are caused by the presence of Sn4+ ions in the system, generating Cr2+ ions. The observed change in structure is caused by Jahn-Teller effect, occurring in the presence of Cu2+ and Cr2+ ions [46].
5
Content available Multifunctionality of multiferroic-based eutectic composites
Orliński K.
Materiały Elektroniczne
|
2010
|
T. 38, nr 3-4
35-39
EN
The present work is dedicated to the functional description of eutectic composites containing rare earth ferrite - REFeO3. Materials that fall under this cathegory exhibit the spontaneous dielectric and magnetic polarization - they behave as ferroelectrics and ferromagnets and can be "tuned" by small additions of other rare earth elements without causing large crystal lattice distortions. Special attention was paid to multifunctionality that, in the majority of cases, comes from the control of the structural refinement with the supercooling of the crystallizing liquid.
PL
Niniejsza praca poświęcona jest opisowi funkcjonalności eutektycznych kompozytów na osnowie ferrytów metali ziem rzadkich - REFeO3. Materiały należące do tej grupy wykazują jednocześnie spontaniczną polaryzację dielektryczną (ferroelektryczność) i magnetyczną (ferromagnetyzm) a ponadto dają się "stroić" za pomocą domieszek innych metali ziem rzadkich nie powodując silnych zniekształceń sieci krystalicznej. Szczególną uwagę zwrócono na wielofunkcjonalność wynikającą w dużej mierze z możliwości sterowania rozdrobnieniem struktury za pomocą zmiany przechłodzenia krystalizującej cieczy.
6
Content available remote Room temperature ferromagnetism in Si nanocaps on self-assembled glass beads
Chi Y. C., Liou Y.
Materials Science Poland
|
2010
|
Vol. 28, No. 4
823--832
EN
Based on self-assembly techniques, Si layers of various thicknesses were deposited on glass bead arrays of various dimensions. The experimental results support the view that the self-assembled glass beads of small sizes (i.e., 10 and 20 nm in diameter), covered with a Si layer below 5 nm in thickness, can induce ferromagnetism. Regularity in the saturation magnetization confirms that the ferromagnetic-like behaviours heavily depend on both the size of the glass beads as well as the thickness of Si nanocaps. Maximum magnetization (750 emu/cm3) was found in the 20 nm glass bead template on which was deposited an ultra-thin 1 nm Si layer. We suggest that the quantum confinement mechanism helps to promote the unpaired electrons, which interact with neighbouring counterparts through the tunnelling effect and, thus, contribute to room temperature ferromagnetism.
7
Content available remote Ferromagnetic and spin-glass properties of single-crystalline U2NiSi3
Szlawska M., Pikul A., Kaczorowski D.
Materials Science Poland
|
2007
|
Vol. 25, No. 4
1267--1273
EN
A single crystal of U2NiSi3 was investigated by means of magnetization, electrical resistivity and heat capacity measurements. Whereas the DC magnetic data clearly manifest strongly anisotropic ferromagnetism, the AC magnetic susceptibility data are consistent with spin-glass behaviour, reported previously for polycrystalline samples. Moreover, no distinct anomalies around TC occur in the specific heat and electrical resistivity characteristics. Altogether the results obtained for single-crystalline U2NiSi3 indicate rather an unusual state of coexistence of ferromagnetism and spin-glass freezing.
8
Content available remote High resolution and analytical electron microscopy of ZnO layers doped with magnetic ions for spintronic applications
Abouzaid M., Ruterana P., Liu C., Morkoc H.
Optica Applicata
|
2006
|
Vol. 36, nr 2-3
311-320
EN
We have investigated the effect of temperature on the crystalline quality of (Zn, Mn)O thin films prepared by rf magnetron sputtering using c-plane sapphire substrates. The layers comprised an Mn doped part towards the surface on top of about a 150 nm pure ZnO layer. They exhibit a columnar structure depending on the deposition temperature; the adjacent domains are rotated from one another by 90°, putting [1010] and [1120] directions face to face. At high Mn concentration this columnar structure is blurred by the formation of Mn rich precipitates for which we report on the structure, composition and crystallographic relationships with the surrounding matrix.
9
Content available remote Sensory GMR jako praktyczne zastosowanie odkryć spintroniki
Majewski J.
Napędy i Sterowanie
|
2005
|
R. 7, nr 4
58--61
PL
Do niedawna za najważniejszą właściwość elektronu uważano to, że jest on nośnikiem elementarnego ładunku elektrycznego. Fakt, iż elektrony posiadają także spin, czyli że nieustannie wirują wokół własnej osi jak miniaturowe żyroskopy i ten ruch wirowy naładowanego elektronu nadaje mu spinowy moment magnetyczny - był istotny głównie przy objaśnianiu zjawiska ferromagnetyzmu.
10
Synthesis of Ferromagnetic Cu3IICrIII-Type Heterotetranuclear Complexesv with Oxalato Bridges
Li Y., Yan C., Guan H.
Polish Journal of Chemistry
|
2004
|
Vol. 78 / nr 1
9-18
EN
Three new _-oxalato-bridgedCu3 IICrIII-type heterotetranuclear complexes have been synthesized and identified as: [Cu3Cr(ox)3(phen)3](ClO4)3 (1), [Cu3Cr(ox)3(Me2phen)3](ClO4)3 (2) and [Cu3Cr(ox)3(NO2phen)3](ClO4)3 (3), where ox represents the oxalato dianions; phen, Me2phen and NO2phen represent 1,10-phenanthroline; 2,9-dimethyl-1,10-phenanthroline or 5-nitro-1,10-phenanthroline respectively. These complexes are the first examples of [Cu3 IICrIII] species bridged by oxalato groups. The three complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR, ESR and electronic spectral studies, these complexes are proposed to have oxalato-bridged structure consisting of three copper(II) ions and a chromium(III) ion, in which the chromium(III) ion has an octahedral environment, and the three copper(II) ions have a square-planar environment.Variable temperature magnetic susceptibility (4.2~300 K) measurements and studies of the complexes (1) and (2) revealed the occurrence of an intramolecular ferromagnetic interaction between the copper(II) and chromium(III) ions through the oxalato-bridge within each molecule. The magnetic data have been also used to deduce the indicated _-oxalato-bridged [Cu3 IICrIII] tetranuclear structure. On the basis of the spin Hamiltonian operator,_ _ _ _ _ _ _ H= 2J(S S S S S S Cu1 Cr Cu2 Cr Cu3 Cr Ĺ + Ĺ + Ĺ ), the magnetic analyses were carried out for the two CuII-CrIII heterotetranuclear complexes and the spin-coupling constants (J) were evaluated as +10.97 cm-1 for (1) and +9.28 cm-1 for (2), indicating that the bridging oxalato would be able to transmit ferromagnetic interaction in the strict orthogonality [Cu3 IICrIII] tetranuclear system.
11
Content available remote Ferromagnetic shape memory alloys: an overview
Cesari E., Pons J., Santamarta R., Segui C., Chernenko V. A.
Archives of Metallurgy and Materials
|
2004
|
Vol. 49, iss. 4
779-789
EN
Ferromagnetic shape memory alloys (FSMA) have the unique capability to exhibit the thermoelastic martensitic transformation and rearrangement of martensitic variants by applying a magnetic filed, in addition to temperature and/or stress changes as in conventional shape memory alloys. The different mechanisms which can produce a shape change under a magnetic field and their relation with the magnetocrystalline anisotropy are discussed. The transformation sequences and martensitic structures are reviewed, particularly in Ni-Mn-Ga alloys as the best known system and representative of the martensites appearing in most FSMA systems. Some transformation features of more recently developed FSMA, namely Ni-Co-Al and Co-Ni-Ga, are also considered.
PL
Ferromagnetyczne stopy z pamięcią kształtu (FSMA) wykazuja inikalną zdolność do termospręzystej przemiany martenzytycznej i reorganizacji wariantów martenzytu w polu magnetycznym, w dodatku do przemian wywołanych zmianami temperatury i/lub naprężeniam, podobnych jak w konwencjonalnych stopach z pamięcią kształtu. w pracy przedyskutowano różne mechanizmy, które mogą wytwarzać zmianę kształtu w polu magnetycznym i ich związek z anizotropią magnetyczną. Przedstawiono przegląd sekwencji przemian i struktur martenzytu, w szczególności w stopach Ni-Mn-Ga, jako należacych do układu najlepiej znanego i reprezenattywnego dla wiekszości ferromagnetycznych stopów z pamięcią kształtu. Pewne cechy charakterystyczne przemiany w ostatnio rozwijanych ferromagnetycznych stopach z pamiecią kształtu Ni-Co-Al i Co-Ni-Ga zostały także przedyskutowane.
12
Spin-entropy driven charge transfer phase transition in iron mixed-valence system
Kojima N., Itoi M., Ono Y., Okubo M., Enmoto M.
Materials Science
|
2003
|
Vol. 21, No. 2
181-189
EN
We have synthesized iron mixed-valence complexes, (n-CnH2n+1)4N[FeIIFeIIIX3] (X = mto(C2O3S), dto(C2O2S2), tto(C2OS3)) and have investigated their physical properties by means of 57Fe Mössbauer spectroscopy, magnetic susceptibility and electrical resistivity measurements. From the analysis of 57Fe Mössbauer spectra, magnetic susceptibility and electrical resistivity, we have discovered a new type of first order phase transition around 120°K for (n-CnH2n+1)4N[FeIIFeIII(dto)3](n = 3, 4), where the charge transfer transition between FeII and FeIII occurs reversibly. In the higher temperature phase, the FeIII (S = 1/2) and FeII (S = 2) sites are coordinated by six S atoms and six O atoms, respectively. In the lower temperature phase, on the other hand, the FeIII (S = 5/2) and FeII (S = 0) sites are coordinated by six O atoms and six S atoms, respectively. Moreover, we have found the ferromagnetic phase transition in this system. The ferromagnetic order is induced by the charge transfer interaction between the FeIII and FeII sites. Moreover, we propose various multifunctional properties for (n-CnH2n+1)4N[FeIIFeIII(mto)3] and (n-CnH2n+1)4N[FeIIFeIII(tto)3].
13
Ferromagnetyzm cienkich warstw i supersieci GaMnAs/GaAs
Sadowski J., Kanski J., Karlsteen M., Svedlindh P., Mathieu R., Domagała J. Z., Bąk-Misiuk J.
Elektronika : konstrukcje, technologie, zastosowania
|
2001
|
Vol. 42, nr 8-9
7-11
EN
GaMnAs is a semiconductor exhibiting low temperature (below 110 K) ferromagnetic phase transition caused by interactions of carriers (holes) with Mn spins. The paper presents properties of thin GaMnAs layers with Mn conaAs spacer. This dependence is presented for structures with two different thickness of GaMnAs layers - 12 and 16 molecular layers (34 Å and 45 Å). In both cases the ferromagnetism in GaMnAs/GaAs superlattice structures was not observed ofor GaAs spacer layer thickness bigger than 9 molecular layers (25 A). This is tentatively explained by the thickness dependent profile of concentration of carriers (holes) in GaMnAs.
14
Sintering effects in superconductor/ferrite composites.
Kopia-Zastawa A., Suliga I., Fremy M.A., Pischedda M.H., Gavarri J.R., Jasieńska S.
Inżynieria Materiałowa
|
1998
|
R. XIX, nr 4
876-879
EN
Granular superconductor/ferrite composites have been fabricated using various sintering conditions such as: volume fraction, sintering temperature and sintering time. The superconducting phase is the well known Bi (Pb)-2223 phase with Tc=110K. The ferrite is NiFe2O4. Using magnetic measurements, X-ray diffraction, scanning electron microscopy and susceptibility measurements the composites after sintering have been characterized.
15
Magnetization and structure of Fe-Al powders.
Fujii M., Saito K., Wakayama K., Kawasaki M., Yoshioka T., Isshiki T., Nishio K., Shiojiri M.
Inżynieria Materiałowa
|
1998
|
R. XIX, nr 4
860-863
EN
A few micrometers-sized Fe1-xAlx (x=0.35-0.42) powders prepared by atomizing method have the B2 structure and are paramegnetic. The powder milled for several hours is magnetized and has a spontaneous magnetization as great as 100 emu/g. The milled powder particles become flakes, which are composed of lamellae expanding parallel to the (110) plane and having heavily distorted lattice. High-resolution transmission electron microscopy and electron diffraction revealed that structures appear in very thin areas within the lamellae. These superlattices indicate the creation of large number of antiphase boundaries, which induce ferromagnetism. When the milled powder is heated at 100-400 degrees centigrade the magnetization decreases to a few tens emu/g, the lamella structures being kept.
16
Content available remote Fixed point technique in computing eddy currents within ferromagnetic conductors exposed to transverse magnetic field
Peterson W.
Archives of Electrical Engineering
|
1998
|
Vol. 47, nr 1
57-68
EN
Eddy currents induced by an alternating transverse magnetic field in elongated ferromagnetic conductors of arbitrary but uniform cross-section are investigated. The problem, in general, leads to an open boundary field, which is analysed here by a hybrid approach, consisting of Galerkin's formulation in finite element terms coupled with a separation of variables. The obtained system of nonlinear equations is solved by means of a fixed point technique based on Brouwer's theorem. A numerical example is performed for conductors of an elliptic cross-section. An influence of the direction of an exciting field on eddy current losses is illustrated.
PL
Badane są prądy wirowe indukowane przez zmienne, poprzeczne pole magnetyczne w wydłużonych przewodach ferromagnetycznych o dowolnym ale jednorodnym kształcie przekroju poprzecznego. To otwarte zagadnienie brzegowe analizuje się stosując podejście hybrydowe, na które składają się sformułowanie Galerkina w metodzie elementów skończonych w powiązaniu z metodą rozdzielenia zmiennych. Wynikający stąd układ równań nieliniowych rozwiązano stosując metodę punktu stałego opartą na twierdzeniu Brouwera. Przedstawiono przykład numeryczny dla przewodnika staliwnego o przekroju eliptycznym. Pokazano wpływ kierunku pola zewnętrznego na straty mocy od prądów wirowych.
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