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1
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
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2016
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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.
2
Content available remote Wpływ substytucji kationowej na strukturalne i magnetyczne właściwości wybranych chromitów selenowych
Jendrzejewska I.
Wiadomości Chemiczne
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2010
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[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].
3
Content available Multifunctionality of multiferroic-based eutectic composites
Orliński K.
Materiały Elektroniczne
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2010
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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.
4
Zastosowanie magnetorezystywnych czujników pola magnetycznego dla kontroli ruchu na powierzchni lotnisk
Fiett J.
Postępy Radiotechniki
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2008
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T. 53, Nr 157
10-18
5
Content available remote Nagroda FNP dla Tomasza Dietla
Gaj J.
Postępy Fizyki
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2007
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T. 58, z. 2
50-52
6
Content available remote Carbon encapsulated iron nanowires
Ramirez R., Weissmann M., Garcia G., Kiwi M.
Materials Science Poland
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2006
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Vol. 24, No. 4
883--890
EN
A study of the structural and magnetic properties of carbon encapsulated iron nanowires is presented. The influence of carbon presence on iron magnetic ordering by means of an ab initio computer simulation has been studied. For wires tightly encapsulated, i.e. with large ratio of wires and nanotubes radii, the presence of carbon strongly alters Fe magnetic configuration of free standing wires, in some cases yielding antiferromagnetic ordering. The energy differences between ferromagnetic and antiferromagnetic phases are small enough to allow their coexistence in a nanowire, which is in agreement with the experimental evidence of exchange-bias in such systems.
7
Content available remote Magnetyzm węgla
Coey M., Sanvito S.
Postępy Fizyki
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2005
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T. 56, z. 3
122-127
EN
Carbon is about to join the list of ferromagnetic elements, but the origins of its magnetic properties remain a mystery.
8
Content available remote Sensory GMR jako praktyczne zastosowanie odkryć spintroniki
Majewski J.
Napędy i Sterowanie
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2005
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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.
9
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
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2001
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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.
10
Sintering effects in superconductor/ferrite composites.
Kopia-Zastawa A., Suliga I., Fremy M.A., Pischedda M.H., Gavarri J.R., Jasieńska S.
Inżynieria Materiałowa
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1998
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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.
11
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.
12
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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