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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:
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:
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:
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:
Quantum versus Classical Polarons in a Ferromagnetic $CuO_3$-Like Chain
Autorzy:
Bieniasz, K.
Oleś, A.
Powiązania:
https://bibliotekanauki.pl/articles/1374771.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.Di
75.10.Pq
75.50.Dd
79.60.-i
Opis:
We present an exact solution for an itinerant hole added into the oxygen orbitals of a $CuO_{3}$-like ferromagnetic chain. Using the Green function method, the quantum polarons obtained for the Heisenberg SU(2) interaction between localized Cu spins are compared with the polarons in the Ising chain. We find that magnons with large energy are favorable towards quasiparticle existence, even in the case of relatively modest electron-magnon coupling. We observe two quasiparticle states with dispersion ~2t each, which emerge from the incoherent continuum when the exchange coupling J increases. Quantum fluctuations in the spin system modify the incoherent part of the spectrum and change the spectral function qualitatively, beyond the bands derived from the perturbation theory.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-80-A-83
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:
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:
Effect of Vanadium Substitution of Cobalt in $NdCo_2Si_2$
Autorzy:
Chowdhury, R.
Dhara, S.
Bandyopadhyay, B.
Powiązania:
https://bibliotekanauki.pl/articles/1402070.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Lp
75.50.Gg
75.50.Ee
75.50.Cc
75.50.Dd
Opis:
In NdCo₂Si₂, partial substitution of Co by V having a larger atomic radius results in negative pressure affecting the magnetic properties of the compound. The samples $Nd(Co_{1-x}V_{x})_Si_2$ (x=0, 0.20, 0.35) have been prepared and characterized using X-ray diffraction. The parent compound NdCo₂Si₂ is antiferromagnetic with $T_{N}$ of 34 K whereas the temperature dependence of inverse susceptibility in the doped samples show ferrimagnetic behaviour below 45 K. From the magnetic field dependence of magnetization and the coercive fields obtained from hysteresis loops, the doped samples exhibit ferromagnetism below ≈ 20 K. The specific heat studies compare the magnetic transitions in the parent and doped samples. $Nd(Co_{0.65}V_{0.35})_2Si_2$ shows a magnetoresistance of 15% at 4 K.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 530-532
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:
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:
Electrical and Magnetic Characterization οf $ZnCr_{2-x}V_{x}Se_{4}$ Spinel Semiconductors
Autorzy:
Duda, H.
Malicka, E.
Groń, T.
Pacyna, A.
Kusz, J.
Powiązania:
https://bibliotekanauki.pl/articles/1791367.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Jc
75.50.Pp
75.50.Dd
Opis:
Single crystals of $ZnCr_{2}Se_{4}$ spinel doped with vanadium were prepared by chemical vapour transport. The chemical compositions of three crystals have been determined by X-ray diffraction. The structure refinement using the SHELXL-93 program system determine the cation distribution in the system as $ZnCr_{2-x}V_{x}Se_{4}$. For x values equal to 0.03, 0.1 and 0.13 the observed symmetry was cubic, space group Fd3m. Based on the structural data, influence of the V ions on the magnetic and electrical properties has been analyzed.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 962-963
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferromagnetic Order in Single-Crystalline (Cd$\text{}_{x}$Al$\text{}_{y}$)[Cr$\text{}_{2}$]Se$\text{}_{z}$ Semiconductors
Autorzy:
Duda, H.
Rduch, P.
Malicka, E.
Groń, T.
Kusz, J.
Powiązania:
https://bibliotekanauki.pl/articles/2048125.pdf
Data publikacji:
2011-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Jc
75.50.Pp
75.50.Dd
Opis:
Measurements of the magnetic properties, the electrical conductivity and the Seebeck effect were performed on single crystals (Cd$\text{}_{x}$Al$\text{}_{y}$)[Cr$\text{}_{2}$]Se$\text{}_{z}$ between 77 and 300 K. All samples have a ferromagnetic order with the Curie temperature of 130 K and the paramagnetic Curie-Weiss temperature of 155 K. Both these temperatures do not depend significantly on the Al substitution. The electrical conductivity of single crystals CdCr$\text{}_{2}$Se$\text{}_{4}$ doped with Al was p-type and showed the change of log σ versus 1/T slope above 150 K. This fact is interpreted as being due to the onset of impurity conduction and structural defects.
Źródło:
Acta Physica Polonica A; 2011, 119, 5; 702-704
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity Study of GaN Highly Doped by Transition Metals
Autorzy:
Gosk, J.
Boćkowski, M.
Tokarczyk, M.
Kowalski, G.
Twardowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399142.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Ha
74.70.-b
74.25.Dw
75.50.-y
61.72.Dd
81.10.Dn
Opis:
GaN:Cr and GaN:Fe single crystals as well as GaN:Mn micropowders highly doped by transition metals were grown to investigate low temperature superconductivity. Magnetic measurements revealed type I superconductivity with $T_{C} ≈ 6 K$ and $H_{C} ≈ 600 Oe$, identical for all compounds and also identical to that observed before in GaP:Cr and GaAs:Cr. The presence of amorphous inclusions of gallium may explain existing superconductivity as a result of a phase transition leading to β-Ga during cooling down of the sample. Since the observed parameters are close to those characteristic for superconducting Ga(II) this possibility could not be ruled out.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 877-880
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:
Electrical and Magnetic Studies of the $Cd_{x}Cr_{y}V_{z}Se_{4}$ Spinels
Autorzy:
Groń, T.
Duda, H.
Malicka, E.
Zawisza, B.
Krok-Kowalski, J.
Pacyna, A.
Powiązania:
https://bibliotekanauki.pl/articles/1791407.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Jc
75.50.Pp
75.50.Dd
Opis:
The electrical and magnetic investigations carried out on the polycrystalline spinels with the general chemical formula $Cd_{x}Cr_{y}V_{z}Se_{4}$ (where z = 0.06, 0.12, 0.24, and 0.31) revealed semiconducting and ferromagnetic properties with a Curie temperature of 127.5 K. A step-like structure of the electrical conductivity, σ(T), was observed for the polycrystal containing 6% V ions in the octahedral sites while the remaining samples showed a typical Arrhenius behaviour of σ(T). These effects are interpreted in terms of ferromagnetic spin clusters which finally dissolve on going towards the paramagnetic limit including non-stoichiometry.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 969-970
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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