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Wyświetlanie 1-15 z 29
Tytuł:
Magnetic Properties of Zinc Doped Ferrites
Autorzy:
Abd El-Ati, M. I.
Kafafy, Aziz M.
Tawfik, A.
Powiązania:
https://bibliotekanauki.pl/articles/1887816.pdf
Data publikacji:
1991-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Gg
75.50.Dd
Opis:
A series of samples of the system Co$\text{}_{1-x}$Zn$\text{}_{x}$Fe$\text{}_{2}$O$\text{}_{4}$ (x = 0.0, 0.3, 0.4, 0.5 and 0.8) have been prepared by the usual ceramic technique. X-ray analysis shows that they are cubic spinel (single phase). The lattice parameter a and the bulk density D are measured for the samples. The substitution experiments replacing Co$\text{}^{2+}$ by Zn$\text{}^{2+}$ furnish new significant fact concerning the magnetic behaviour of ferrites. The magnetic strength of the magnetic ions on the Band A-sites can be varried relative to each other by the substitution of Zn$\text{}^{2+}$. The increase of density of the composition increases the magnetic interaction of the dipole moment at the B-sites.
Źródło:
Acta Physica Polonica A; 1991, 79, 6; 889-894
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferromagnetism in Cr-Based Diluted Magnetic Semiconductors
Autorzy:
Blinowski, J.
Kacman, P.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/1933725.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Gm
75.50.Pp
75.50.Dd
Opis:
It has been recently established that in zinc chalcogenides with Cr$\text{}^{2+}$ paramagnetic ions the p-d interactions are ferromagnetic. We clarify the origins of this property and make predictions concerning other Cr-based diluted magnetic semiconductors. The observation of the ferromagnetic p-d interaction resuscitated hopes for ferromagnetic d-d exchange interactions in diluted magnetic semiconductors. We have calculated the nearest-neighbor superexchange integrals in Cr-based diluted magnetic semiconductors. No simple correlation between the signs of p-d and d-d interactions has been found. Still, there are extended energy regions where the calculated superexchange is ferromagnetic and the act ual parameters of DMS with Cr$\text{}^{2+}$ seem to match these regions.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 683-686
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferromagnetic Ground State of Two-Band Hubbard Model with One Electron per Site
Autorzy:
Schulenburg, J.
Richter, J.
Powiązania:
https://bibliotekanauki.pl/articles/1955522.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Mg
75.30.Et
75.50.Dd
75.10.Lp
Opis:
We study the multiband mechanism to favour a ferromagnetic insulating ground state within a two-band Hubbard model. Besides perturbation theory we use exact diagonalization studies to examine the ground state of chains and 2D-lattices. According to second order perturbation theory the exact diagonalization yields a fully polarized ferromagnetic ground state, if the hopping between two ground state orbitals of neighbouring atoms t$\text{}_{gg}$ is small and the hopping between a ground state orbital and an excited orbital t$\text{}_{ge}$ dominates. However, in contrast to the suggestion from the second order perturbation theory this ferromagnetic state is stable only for very small hopping integrals U≫ t$\text{}_{ge}$>t$\text{}_{gg}$. For larger t $\text{}_{ge}$ quantum interference effects lead to complex magnetic structures.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 367-370
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferromagnetism in II-VI Based Semiconductor Structures
Autorzy:
Cibert, J.
Ferrand, D.
Tatarenko, S.
Wasiela, A.
Kossacki, P.
Dietl, T.
Powiązania:
https://bibliotekanauki.pl/articles/2027470.pdf
Data publikacji:
2001-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
75.50.Pp
75.30.Hx
75.50.Dd
Opis:
The experimental results on carrier-induced ferromagnetic interaction in II-VI diluted magnetic semiconductors are shortly reviewed and analyzed in the light of the mean field approximation. We particularly take the point of view of the experimentalist to emphasize (i) points which are easily understood within this simple model (as the role of the detailed structure of the valence band) and hence should be incorporated into more sophisticated models, and (ii) points which are not taken into account in the mean field model (e.g., disorder effects) and hence call for more elaborate descriptions. We particularly discuss the case of a low carrier density, and show that the situation appears as experimentally very different in the highly disordered 3D layers and in the modulation doped 2D quantum wells.
Źródło:
Acta Physica Polonica A; 2001, 100, 2; 227-236
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Kinetic Exchange in A$\text{}^{III}$B$\text{}^{V}$ Diluted Magnetic Semiconductors
Autorzy:
Blinowski, J.
Kacman, P.
Powiązania:
https://bibliotekanauki.pl/articles/2027499.pdf
Data publikacji:
2001-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Gm
75.50.Dd
75.30.Et
Opis:
In the case of II-VI diluted magnetic compounds it was shown that the kinetic exchange mechanism depends crucially on the electronic configuration of the magnetic ions and the charge transfer energies for the transitions from the band onto the magnetic ion and vice versa. In the present paper we analyze these effects in the family of III-V diluted magnetic semiconductors, showing that they affect considerably the predictions of the values of the Curie temperature and should be taken into account in the search for room temperature ferromagnetism in diluted magnetic semiconductors.
Źródło:
Acta Physica Polonica A; 2001, 100, 3; 343-349
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Control of Ferromagnetism in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te Based Quantum Wells
Autorzy:
Bertolini, M.
Boukari, H.
Ferrand, D.
Cibert, J.
Tatarenko, S.
Gilles, B.
Maślana, W.
Gaj, J. A.
Kossacki, P.
Dietl, T.
Powiązania:
https://bibliotekanauki.pl/articles/2035587.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Hx
75.50.Dd
75.50.Pp
78.55.Et
Opis:
New structures aiming at controlling the ferromagnetic properties of diluted magnetic semiconductor quantum wells are presented. The carrier density is controlled by applying a voltage across a p-i-n diode. A new method, creating a 2D hole gas by adjusting the distance between the quantum well and surface, offers opportunities for a broader range of structures.
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 603-608
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetic Properties of Low Temperature Annealed Ga$\text{}_{1-x}$Mn$\text{}_{x}$As
Autorzy:
Kuryliszyn, I.
Wojtowicz, T.
Liu, X.
Furdyna, J. K.
Dobrowolski, W.
Broto, J.-M.
Goiran, M.
Portugall, O.
Rakoto, H.
Raquet, B.
Powiązania:
https://bibliotekanauki.pl/articles/2035604.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.50.Dd
81.40.Rs
Opis:
We present the results of low temperature annealing studies of Ga$\text{}_{1-x}$Mn$\text{}_{x}$As epilayers grown by low temperature molecular beam epitaxy in a wide range of Mn concentrations (0.01
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 659-665
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of EuBaCo$\text{}_{2}$O$\text{}_{5.5}$ Single Crystals
Autorzy:
Baran, M.
Barilo, S. N.
Bychkov, G. L.
Gatalskaya, V. I.
Kurochkin, L. A.
Shiryaev, S. V.
Szymczak, R.
Szymczak, H.
Powiązania:
https://bibliotekanauki.pl/articles/2037131.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Cr
75.50.Dd
75.30.Gw
75.30.Kz
Opis:
The static magnetization of the EuBaCo$\text{}_{2}$O$\text{}_{5.5}$ single crystals was measured from helium to room temperatures for two configurations of the applied field: parallel and perpendicular to the c-axis. The compound is antiferromagnetic from helium temperature to about 210 K. In low temperature region (below 45 K) the antiferromagnetism coexists with a spin-glass-like state. The metamagnetic field-induced phase transition was observed in the antiferromagnetic phase for magnetic field applied perpendicular to the c-axis. The spontaneous phase transition from antiferromagnetic to weak ferromagnetic phase was established to be of the first order. This transition is accompanied by the appearance of the intermediate state. The weak ferromagnetic phase exists up to T$\text{}_{c}$=240 K.
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 209-214
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New Discussion of the Spin Dynamics of Paramagnetic EuO
Autorzy:
Latacz, Z.
Powiązania:
https://bibliotekanauki.pl/articles/2038379.pdf
Data publikacji:
2004-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Gb
75.40.Cx
75.50.Dd
Opis:
The simplest approximations for a continued-fraction representation of the dynamic relaxation function are used to investigate the spin dynamics of paramagnetic EuO. As the result we can see how the considered approximations predict those wavevectors for which a "spin wave" peak appears in the spectrum. Furthermore, the calculated position of this peak is compared with experiment. The correlation theory within the two-pole approximation is presented in a simple and analytic form.
Źródło:
Acta Physica Polonica A; 2004, 106, 4; 515-528
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structure and Transport Properties of La$\text{}_{0.75-x}$RE$\text{}_{x}$Ca$\text{}_{0.25}$MnO$\text{}_{3}$ (RE = Gd, Dy, Ho; 0≤ x≤0.75) Manganites
Autorzy:
Drozd, V.
Pękała, M.
Kovac, J.
Skorvanek, I.
Szymański, M.
Nedilko, S.
Powiązania:
https://bibliotekanauki.pl/articles/2041482.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.47.Lx
71.38.-k
72.20.Ee
75.50.Dd
Opis:
Structure and transport properties have been studied for a series of La$\text{}_{0.75-x}$RE$\text{}_{x}$Ca$\text{}_{0.25}$MnO$\text{}_{3}$ manganites with heavy rare earth ions of Gd, Dy, Ho substituting La with x=0, 0.10, 0.25, 0.50, and 0.75. Polycrystalline samples were prepared by the carbonate precipitation route. The oxygen content was determined by the iodometric titration. The X-ray investigations carried out by the powder method show that the unit cell volume gradually decreases and orthorhombic distortion of the lattice increases with rising RE content. Below the room temperature the electrical resistivity is of the semiconducting type for all the samples studied. Electrical resistivity vs. temperature dependences were analyzed within different models: simple thermal activation, Mott's variable range hopping, adiabatic, nonadiabatic, and bipolaron. The Curie temperatures of Gd, Dy, and Ho substituted manganites determined from magnetization measurements show that at 280 K all the samples are in the paramagnetic phase. The increasing RE fraction reduces magnetization at 4 K as compared to La$\text{}_{0.75}$Ca$\text{}_{0.25}$MnO$\text{}_{3}$.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 751-758
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Heterostructure Formed from Hole- and Electron-Doped Lanthanum Manganites
Autorzy:
Vengalis, B.
Rosa, A. M.
Devenson, J.
Šliužienė, K.
Lisauskas, V.
Oginskis, A.
Anisimovas, F.
Pyragas, V.
Powiązania:
https://bibliotekanauki.pl/articles/2041760.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Cg
73.40.Lg
75.50.Dd
Opis:
High crystalline quality films of n-La$\text{}_{2}\text{}_{/}\text{}_{3}$ Ce$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$, p-La$\text{}_{2}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ and related p-n diode structures were grown heteroepitaxially on lattice-matched SrTiO$\text{}_{3}$(100) substrates by dc magnetron sputtering and pulsed laser deposition. The La$\text{}_{2}\text{}_{/}\text{}_{3}$ Ce$\text{}_{1}\text{}_{/}\text{}_{3}$ Mn O$\text{}_{3}$/La$\text{}_{2}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ bilayer was patterned into a strip-like geometry to investigate electrical properties of the interface. Significant magnetoresistance values and nonlinear current-voltage characteristics were indicated for the interface of the p-n diode heterostructure.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 290-293
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Competing Magnetic Interactions in Zn$\text{}_{3}$Fe$\text{}_{4}$V$\text{}_{6}$O$\text{}_{24}$ Studied by Electron Paramagnetic Resonance
Autorzy:
Zolnierkiewicz, G.
Guskos, N.
Typek, J.
Blonska-Tabero, A.
Powiązania:
https://bibliotekanauki.pl/articles/2046813.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.-v
75.50.Dd
75.50.Ee
Opis:
A multicomponent vanadate M$\text{}_{3}$Fe$\text{}_{4}$V$\text{}_{6}$O$\text{}_{24}$ sample with non-magnetic M = Zn(II) ions was synthesized by the solid state reaction method using stoichiometric mixtures of the 80mol% FeVO$\text{}_{4}$ and 20mol% Zn$\text{}_{3}$(VO$\text{}_{4}$)$\text{}_{2}$. The temperature dependence of the EPR spectra was performed in the 90-280 K temperature range. The resonance field and the integrated intensity of the EPR line showed minimum value of both parameters at≈200 K. It is suggested that a part of the sample is displaying tendency to form an antiferromagnetic ordered state (or the magnetic clusters) above this temperature while below the ferromagnetic interaction of the main part of material is dominating. This behaviour is attributed to the inherent magnetic inhomogeneity of the system due to the presence of the ferromagnetic or antiferromagnetic spin clusters.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 675-679
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Negative Magnetisation and Absence of Superconductivity in RFe$\text{}_{4}$Al$\text{}_{8}$ (R=Lu, Yb) Compounds
Autorzy:
Andrzejewski, B.
Kowalczyk, A.
Toliński, T.
Powiązania:
https://bibliotekanauki.pl/articles/2046747.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Dd
75.50.-y
75.50.Ee
51.60.+a
74.70.-b
Opis:
We report researches for superconductivity and the effect of negative magnetisation in the RFe$\text{}_{4}$Al$\text{}_{8}$ (R = Lu, Yb) compounds by means of magnetic measurements and microwave absorption. Contrary to the earlier reports we do not confirm the existence of any traces of superconductivity in these compounds. Instead of the superconductivity and the Meissner effect, the YbFe$\text{}_{4}$Al$\text{}_{8}$ compound exhibits the effect of negative magnetisation, whereas the LuFe$\text{}_{4}$Al$\text{}_{8}$ compound shows an exact antiferromagnetic behaviour.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 561-564
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Observation of Superconductivity in Highly Cr-Doped GaP Single Crystals
Autorzy:
Gosk, J. B.
Strzelecka, G.
Kowalski, G.
Hruban, A.
Kamińska, M.
Twardowski, A.
Gronkowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/2046913.pdf
Data publikacji:
2006-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.10.+v
75.50.Pp
61.72.Vv
61.72.Dd
81.10.Dn
Opis:
Studying bulk GaP, highly doped with Cr, and searching for possible ferromagnetic semiconductor in view of spintronic applications, we found superconducting behavior of this material unexpectedly. Magnetization techniques and X-ray diffraction were applied to study these crystals. Magnetization revealed superconducting features up to about 6 K and X-ray studies showed that superconductivity might be related to small size Cr precipitates.
Źródło:
Acta Physica Polonica A; 2006, 110, 2; 189-193
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Layer and Interface Structure of CoFe/Ru Multilayers
Autorzy:
Pym, A.
Lamperti, A.
Cardoso, S.
Freitas, P.
Tanner, B.
Powiązania:
https://bibliotekanauki.pl/articles/1814028.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.10.Kw
68.65.Ac
68.35.Ct
75.50.Kj
85.75.Dd
85.70.Ay
Opis:
Grazing incidence X-ray scattering measurements have been performed to probe the structure of CoFe/Ru layers and their interfaces. It was found that the interface width increased approximately linearly with the layer number from the substrate in a multilayer and that a substantial asymmetry existed between the width of CoFe/Ru and Ru/CoFe interfaces. By co-minimizing both the specular and diffuse scatter with that simulated from a model structure, the topological roughness amplitude was determined to be comparable to the intermixing interface width.
Źródło:
Acta Physica Polonica A; 2007, 112, 6; 1243-1248
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 29

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