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Wyświetlanie 1-15 z 85
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:
Phase Transitions Induced in HoCo$\text{}_{3}$Ni$\text{}_{2}$ Single Crystals
Autorzy:
Zawadzki, J.
Ballou, R.
Gorges, B.
Szymczak, R.
Powiązania:
https://bibliotekanauki.pl/articles/1928269.pdf
Data publikacji:
1993-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.30.Kz
75.50.Gg
75.60.Ej
Opis:
The magnetic studies of temperature and field induced phase transitions were performed on single crystals of HoCo$\text{}_{3}$Ni$\text{}_{2}$ compound. The rotational-type spin reorientation was found between T$\text{}_{SR1}$ = 160 K and T$\text{}_{SR2}$ = 200 K. In the vicinity of T$\text{}_{SR1}$ two different field induced transitions were observed: the first order moment reorientation type transition in the basal plane and the spin reorientation from the easy plane to the c-axis with simultaneous increase in spontaneous magnetization. The intersublattice molecular field coefficient as well as the magnetization anisotropy of Ho sublattice were determined. The observed magnetic behaviour was analysed within the framework of the spin-reorientation model, taking into account the change of the intrinsic states of rare-earth ions caused by their huge anisotropy energy. The thermal variation of the anisotropy constants of the studied compound is also presented.
Źródło:
Acta Physica Polonica A; 1993, 83, 2; 209-218
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cation Distribution in Fe$\text{}_{3(1-\delta)}$O$\text{}_{4}$ and Low Level Doped Fe$\text{}_{3-x}$M$\text{}_{x}$O$\text{}_{4}$, M=Ti, Zn, Al
Autorzy:
Kąkol, Z.
Kozłowski, A.
Sabol, J.
Metcalf, P.
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/1861287.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ga
75.30.Cr
75.50.Gg
Opis:
Systematic magnetic saturation moment and electrical resistivity measurements of the Fe$\text{}_{3(1-\delta)}$O$\text{}_{4}$ and Fe$\text{}_{3-x}$M$\text{}_{x}$O$\text{}_{4}$ (M = Ti, Zn, Al) are presented. Cation distributions for low level doping are proposed and compositional dependencies of the Verwey transition temperature are determined. The latter show striking similarities in their dependence on cation vacancies and dopant concentration for any extraneous cations. These data are the basis for the analysis of the correlation between the presented cations distributions and the Verwey transition.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 223-227
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Single-Ion Rare Earth Anisotropy in ThMn$\text{}_{12}$-Type Compounds
Autorzy:
Stefański, P.
Powiązania:
https://bibliotekanauki.pl/articles/1931244.pdf
Data publikacji:
1994-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.50.Gg
Opis:
The single-ion rare earth anisotropy was investigated in ThMn$\text{}_{12}$-type compounds. For this purpose the crystal electric field parameter values were studied. In these compounds, described by formula RFe$\text{}_{12-x}$T$\text{}_{x}$, R = rare earth, T = Ti, V, Cr, Mo, W and Si, the T atoms have strong crystallographic site preference changing the local crystal electric field potential which "sees" the rare earth ion. The crystal electric field potentials A$\text{}_{2}^{0}$ were calculated considering this site preference. The summations were performed taking into account the nearest neighborhood of the rare earth ion according to the recent results of band structure calculations. The charges of the surrounding Fe and T atoms were established applying the chemical bond model proposed by Pauling. The absolute value of A$\text{}_{2}^{0}$ decreases when the content of vanadium increases in 8(i) position, which is in agreement with experimental data. Localization of Si atoms in 8(j) and 8(f) causes a decrease in A$\text{}_{2}^{0}$. The $\text{}^{155}$Gd Mössbauer spectroscopy data confirm this fact. Miedema's "macroscopic" atom model of cohesion in alloys was applied for interpretation of the role of T atoms in the isomer shift and volume effects.
Źródło:
Acta Physica Polonica A; 1994, 85, 3; 615-621
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Reorientation and Exchange Coupling in the Dy$\text{}_{1-x}$Er$\text{}_{x}$Fe$\text{}_{10}$Si$\text{}_{2}$ Compounds
Autorzy:
Stefański, P.
Kowalczyk, A.
Skoryna, D.
Szlaferek, A.
Wrzeciono, A.
Powiązania:
https://bibliotekanauki.pl/articles/1929845.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.50.Gg
Opis:
The structural and magnetic properties of Dy$\text{}_{1-x}$Er$\text{}_{x}$Fe$\text{}_{10}$Si$\text{}_{2}$ are investigated. X-ray analysis reveals that these compounds are of the tetragonal ThMn$\text{}_{12}$ structure. In this structure the rare earth atoms occupy one crystallographic position 2(a). The unit cell contains 26 atoms. The spin reorientation temperature, T$\text{}_{SR}$, was measured from the temperature dependence of the initial susceptibility using an ac bridge of mutual inductance of the Harsthorn type. Dy$\text{}^{+3}$ and Er$\text{}^{+3}$ have opposite contributions to the entire magnetic anisotropy. The spin reorientation temperature is found to be about 271 K in DyFe$\text{}_{10}$Si$\text{}_{2}$ and 48 K in ErFe$\text{}_{10}$Si$\text{}_{2}$. The values are discussed applying the crystal field model. The value of the rare earth-transition metal exchange coupling constant J$\text{}_{RFe}$/k$\text{}_{B}$ derived from the mean-field model analysis of the Curie temperature is about -13 K. The Fe-Fe exchange integral is much higher and is equal to about 75 K.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 259-262
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Peculiarities of the Electronic Properties of the κ-Phase Structures (BEDT-TTF)$\text{}_{2}$Cu(N(CN)$\text{}_{2}$)X with X=Cl, Br, I
Autorzy:
Andres, K.
Posselt, H.
Kushch, N.
Kund, M.
Biberacher, W.
Saito, G.
Powiązania:
https://bibliotekanauki.pl/articles/1933335.pdf
Data publikacji:
1995-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Le
75.50.Gg
75.50.Ee
74.70.Kn
Opis:
The structure of the title compounds is similar to other κ-phase structures with respect to the checkerboard-like arrangement of the ET dimers (ET = BEDT-TTF) in the conducting planes, but different by the tilt alternation of these dimers in successive planes. The resulting inequivalence of these planes tends to destabilize the metallic state which becomes extremely sensitive to changes in the S-S overlaps of neighbouring ET molecules. Such changes may result from anion substitution, lattice expansion, or also from ordering effects of the ethylene end groups of the ET molecules. They lead to quite different electronic properties of the three isostructural compounds. We focus especially on the strongly pressure-dependent properties of the Cl-compound, where a coexistence of magnetically ordered and superconducting states with rather spectacular superconducting reentrance effects is observed.
Źródło:
Acta Physica Polonica A; 1995, 87, 4-5; 761-766
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Magnetic Ground State in Thulium Iron Garnets
Autorzy:
Koper, A.
Lehmann-Szweykowska, A.
Wigen, P. E.
Bornfreund, R. E.
Powiązania:
https://bibliotekanauki.pl/articles/1964707.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Lk
75.50.Gg
75.50.-y
75.40.Μg
75.10.Hk
Opis:
Magnetic phase diagrams of thulium iron garnets at Τ = 0 K are obtained by means of the so-called Monte Carlo relaxation method. The diagrams are given in terms of the respective strength of the superexchange couplings. There are five different phases and one spin-flop line on the diagram obtained. Two of these phases are of a semi-spin glass type.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 391-394
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Properties of Tb$\text{}^{3+}$ Ion in TbNi$\text{}_{10}$Si$\text{}_{2}$
Autorzy:
Stefański, P.
Suski, W.
Wochowski, K.
Mydlarz, T.
Powiązania:
https://bibliotekanauki.pl/articles/1964565.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.50.Gg
Opis:
Ground state properties of Tb$\text{}^{3+}$ ion were investigated in the tetragonal ThΜn$\text{}_{12}$-type TbNi$\text{}_{10}$Si$\text{}_{2}$ compound on the basis of temperature dependence of the paramagnetic susceptibility and magnetization measurements. The rare earth temperature dependence of the susceptibility was calculated using the Van Vleck equation. The Γ$\text{}_{t5}^{(1)}$ doublet is suggested to be a ground state separated by 9 K from the first excited singlet Γ$\text{}_{t1}^{(2)}$. The magnetic moment associated with the ground state doublet agrees with saturation magnetization data at 4.2 K. The overall crystal field splitting is estimated to be 105 K.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 281-284
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rhombohedral Distortion in Fe$\text{}_{3-y}$Zn$\text{}_{y}$O$\text{}_{4}$ at Verwey Transition
Autorzy:
Kozłowski, A.
Kąkol, Z.
Zalecki, R.
Knight, K.
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/1955841.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Gg
64.70.Kb
61.12.-q
Opis:
The time-of-flight neutron diffraction data were collected for two Fe$\text{}_{3-y}$Zn$\text{}_{y}$O$\text{}_{4}$ powder samples showing different order of the Verwey transition: y=0.0072 - first order, y=0.0249 - second order. Measurements were performed on spallation neutron source in ISIS Rutherford Appleton Laboratory. At low temperatures (below Verwey transition temperature T$\text{}_{V}$) clear splitting of certain reflections characteristic of rhombohedral distortion was observed for both samples. We found that this distortion is much bigger for the sample exhibiting first-order than for the sample showing second-order transition.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 443-446
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural and Magnetic Properties of Dy(Fe,V,Si)$\text{}_{12}$ Compounds
Autorzy:
Drzazga, Z.
Winiarska, A.
Chrobak, A.
Kaczorowski, D.
Powiązania:
https://bibliotekanauki.pl/articles/1964633.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
75.50.Gg
75.30.Cr
61.10.-i
Opis:
An influence of Si on the structural and magnetic properties of Dy(Fe,V,Si)$\text{}_{12}$ compounds is studied. X-ray diffraction shows that these materials crystallise in the tetragonal ThMn$\text{}_{12}$-type structure. An increase in the saturation magnetization, the Curie temperatures and magnetocrystalline anisotropy in the Si substitutional systems is observed when compared with DyFe$\text{}_{12-x}$V$\text{}_{x}$. The magnetic properties depend on the preferential site occupation and concentration of Si and V atoms in these compounds.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 335-338
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnonic Spectra of Ferromagnetic Composites Versus Magnetization Contrast
Autorzy:
Krawczyk, M.
Puszkarski, H.
Powiązania:
https://bibliotekanauki.pl/articles/1968941.pdf
Data publikacji:
1998-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Gg
Opis:
It had been shown recently that the calculated magnonic spectra of two-dimensional periodic ferromagnetic composites can present frequency ranges forbidden for the propagation of magnon excitations throughout the composite. However, those forbidden energy gaps were found to be highly sensitive to the exchange contrast between the component ferromagnetic materials but were very weakly sensitive to the contrast in spontaneous magnetizations of the two materials. Accordingly, in this paper we introduce a new mathematical definition of the exchange field acting in inhomogeneous medium. With this new definition the present theory gives magnonic spectra reasonably sensitive to magnetization contrast, as they should be from the physical viewpoint; moreover, the magnetization contrast now becomes a gap-creating factor as well.
Źródło:
Acta Physica Polonica A; 1998, 93, 5-6; 805-810
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of 4f-3d Intermetallics Studied by $\text{}^{161}$Dy and $\text{}^{57}$Fe Mössbauer Effect
Autorzy:
Pszczoła, J.
Powiązania:
https://bibliotekanauki.pl/articles/2011002.pdf
Data publikacji:
1999-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.80.+y
75.50.Gg
71.20.Lp
Opis:
Applications of the Mössbauer effect at the $\text{}^{161}$Dy and $\text{}^{57}$Fe nuclei to study heavy rare earth - transition metal compounds are presented. Magnetic hyperfine fields at dysprosium and iron nuclei observed in the Dy$\text{}_{u}$(M-M)$\text{}_{v}$ intermetallics (u/v=2/17, 6/23, 1/3, and 1/2; M-M = Mn-Fe, Fe-Co, and Co-Ni), magnetic moments and magnetic ordering temperatures are discussed. The magnetic hyperfine field at iron nuclei and the field at dysprosium nuclei treated as functions of a number of 3d electrons form two different systems of the Slater-Pauling curves. The magnetic ordering temperatures treated as functions of the number of 3d electrons also form the u/v system of curves. Considering the magnetic data and the magnetic hyperfine fields it can be concluded that intermetallics can be treated as three-subsystem ferrimagnets. Consequently, a coexistence between the 4f, 5d, and 3d magnetism in the rare earth - transition metal compounds can be qualitatively explained.
Źródło:
Acta Physica Polonica A; 1999, 96, 1; 113-122
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
$\text{}^{57}$Fe Hyperfine Field Anisotropy in Ferrites and its Relation to the Non-Uniformity of the Ionic Surrounding
Autorzy:
Štepánková, H.
Englich, J.
Kohout, J.
Powiązania:
https://bibliotekanauki.pl/articles/2013366.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.60.-k
75.50.Gg
Opis:
The hyperfine field anisotropy tensors, obtained from analysis of $\text{}^{57}$Fe NMR spectra for iron sites in various magnetic oxides (barium hexaferrite, lithium spinel, magnetite and yttrium-iron garnet) were used to investigate the relation between the hf anisotropy and surrounding ionic arrangement. While a reasonable correlation has been found when the distribution of the nearest cations was considered, no correlation was obtained between the hyperfine field anisotropy and the positions of the nearest oxygen anions.z
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 757-760
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conductivity and Magnetism of Magnetic Oxides
Autorzy:
Gehring, G. A.
Powiązania:
https://bibliotekanauki.pl/articles/2012877.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.50.Gg
Opis:
In a stoichiometric oxide the energy for the magnetic ordering is due to superexchange. This depends on the virtual transfer of a d electron from the transition ion to the neighbouring oxygen. When the oxide is p-doped there are compensating holes on the oxygen or the transition ion becomes mixed valent. The oxide may then conduct. The same transfer integral enters both the expression for the antiferromagnetic superexchange and the band width of the mobile carriers. Thus materials with a large antiferromagnetic exchange energy will be expected to have a relatively wide conduction band in the doped state and hence to have a high conductivity. In this paper the difference is explored between the materials in which there is true antiferromagnetism and those which are ferrimagnetic. In the antiferromagnets the carriers must destroy the magnetic order as they move. This behaviour is well known from the cuprates. In ferrimagnets the carriers may be able to move entirely on one sublattice. This occurs in Fe$\text{}_{3}$O$\text{}_{4}$ and probably in the doped garnets. In the case where motion is on one sublattice then doping does not destroy the magnetism and there is a relatively small magnetoresistance. An interesting feature is that unlike the cuprates the ferrimagnets do not become good metals at any doping but exhibit hopping conductivity. We explain the apparent paradox that the best conductivity is actually observed in materials where the conduction is only allowed when the antiferromagnetism has been quenched and that the conductivity in ferrimagnets is low.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 175-184
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Manganese on Magnetic and Electrical Properties of the RMn$\text{}_{x}$T$\text{}_{12-x}$ Alloys
Autorzy:
Suski, W.
Wochowski, K.
Mydlarz, T.
Belan, B.
Powiązania:
https://bibliotekanauki.pl/articles/2014385.pdf
Data publikacji:
2000-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Gg
75.20.-g
75.20.En
75.50.Ee
Opis:
The magnetic and electrical properties of the tetragonal, ThMn$\text{}_{12}$-type RMn$\text{}_{x}$T$\text{}_{12-x}$ alloys (R = Y, Ce, Pr, Nd, Sm and T = Fe, Co, Ni) were studied in broad temperature and magnetic field ranges to elucidate an influence of manganese on the magnetic ordering in these materials. Magnetic properties were examined at T=1.7-300K in magnetic field up to 14T, whereas the electrical properties were examined at T=4.2-300K, on the polycrystalline samples. Majority of the samples exhibit ferro- or ferrimagnetic properties. Some samples containing larger concentration of Mn are paramagnetic in the whole temperature range. The electrical resistivity of these alloys shows metallic character.
Źródło:
Acta Physica Polonica A; 2000, 98, 5; 505-511
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 85

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