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V. V. Matveev D. A. Markelov V. I. Chizhik P. Ingman E. Lähderanta 《Russian Chemical Bulletin》2013,62(9):1985-1990
1-Ethyl-3-methylimidazolium acetate was studied by NMR relaxation. The temperature dependences of the spin-lattice relaxation rates (1/T 1) for 1H and 13C were obtained. The curves with maxima were observed for the majority of the temperature dependences 1/T 1, which provided a reliable temperature dependence of the correlation times (τc). In the low-temperature range, the proton relaxation rates tend to an asymptotic value, which is related, most likely, to spin diffusion manifested in the studied samples. The values of correlation times τc calculated for 1H and 13C of the same functional group almost coincide at high temperatures, which confirms that the used approach is adequate for the determination of characteristic times of rotational reorientation of counterions in the studied ionic liquid. 相似文献
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Al. A. Nikitin An. A. Nikitin A. B. Ustinov E. Lähderanta B. A. Kalinikos 《Technical Physics》2016,61(6):913-918
A microwave electrically tunable photonic crystal based on a periodically width-modulated slot transmission line with a ferroelectric film is investigated for the first time. The dispersion and transmission characteristics of electromagnetic waves propagating in such a structure are calculated. The electric control over photonic crystal characteristics is simulated. 相似文献
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T. Kàmàn E. Lähderanta S. Leppävuori I. Halàsz I. Dòdony G. Zsolt T. Porjesz R. Laiho A. Uusimäki I. Kirschner Gy. Kovács 《Zeitschrift für Physik B Condensed Matter》1990,78(2):169-173
Tl–Ca–Ba–Cu–O compounds of the nominal composition of (1, 1, 1, 1) have been prepared from different starting materials and with the same heat treatment process. During the investigation of their properties a diamagnetic signal has been found up to the temperature of 132 K. This hints at the existence of a certain material content distributed into discrete superconducting domains. The parameters of it reflect a superstructure of the (2, 2, 2, 3) and (2, 1, 2, 2) compositions having a time-dependent behaviour. On the basis of the signal levels at 132 K and 4.2 K, the quantity of the high temperature superconducting material is about 0.01% of the total one at liquid He temperatures. 相似文献
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G. S. Dimitriev I. V. Krainov V. F. Sapega N. S. Averkiev J. Debus E. Lähderanta 《Physics of the Solid State》2018,60(8):1568-1577
The energy structure of the Mn acceptor, which is a complex of Mn2+ ion plus valence band hole, is investigated in the external magnetic field and under presence of an uniaxial stress has been studied. The spin-flip Raman spectra are studied under resonant excitation of exciton bound to the Mn acceptor. The gfactors of the ground F = 1 and the first excited F = 2 states are determined and selection rules for the optical transitions between the acceptor states are described. The value of the random field (stress or electric field) acting on manganese acceptor and the deformation potential for the exchange interaction constant of the Mn2+ + hole complex are obtained. A theoretical model is developed that takes into account the influence of random internal and uniaxial external stress and magnetic field. The proposed model describes well the lines of spin-flip Raman scattering of Mn acceptor. 相似文献
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R. Laiho E. Lähderanta L. S. Vlasenko M. P. Vlasenko V. S. Zakhvalinskii 《Physics of the Solid State》2001,43(3):489-492
A change in the electrical conductivity, σ, is observed in the manganese perovskite La1?x CaxMnO3, with x=0 and 0.3 under saturation of the magnetic resonance transitions of Mn ions. This effect has a maximum in the temperature range of the magnetic phase transition of the compounds. Two contributions to the change in σ are found. The first, dominating in LaMnO3, is an increase in σ caused by heating of the sample under magnetic resonance. The second is a σ decrease due to reorientation of the Mn spins, observed in La0.7Ca0.3MnO3. 相似文献
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V. S. Zakhvalinskiĭ R. Laiho K. G. Lisunov E. Lähderanta P. A. Petrenko Yu. P. Stepanov J. Salminen V. N. Stamov 《Physics of the Solid State》2006,48(12):2300-2309
The structural, electrical, and magnetic properties of ceramic perovskite manganites LaMnO3 + δ (δ = 0–0.154) are investigated. It is found that, in a weak magnetic field (B = 2 G), the LaMnO3 + δ manganite with δ = 0.065 at temperatures below the Curie temperature T C of the paramagnet-ferromagnet phase transition has a mixed (spin glass + ferromagnet) phase. In LaMnO3 + δ manganites with the parameter δ = 0.100–0.154, this phase transforms into a frustrated ferromagnetic phase. A similar transformation was observed previously in La1?x CaxMnO3 compounds at calcium contents in the range 0 ≤ x ≤ 0.3. This similarity is explained by the fact that, in both materials, the Mn4+ concentration and, accordingly, the hole concentration c change equally in the concentration range from ~0.13 to 0.34 with an increase in x or δ. However, the magnetic irreversibility, the concentration dependences of the Curie temperature T C(c) and the magnetic susceptibility X(c), and the critical behavior of the temperature dependence of the susceptibility X(T) in the vicinity of the Curie temperature T C differ substantially for these two materials. The observed differences are associated with the distortion of the cubic perovskite structure, the decrease in the degree of lattice disorder, and a more uniform distribution of holes in the LaMnO3 + δ manganites as compared to the La1 ? x CaxMnO3 compounds. 相似文献
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A. C. Bódi R. Laiho I. Kirschner E. Lähderanta 《Zeitschrift für Physik B Condensed Matter》1997,104(1):33-36
Low-frequency ac susceptibility measurements on ceramic YBCO superconductors carried out at the presence of a quasi-one-dimensional temperature gradient are compared with those made without the temperature gradient. The values of the different characteristic temperatures measured on samples without and with a temperature gradient are identical but in the second case itch characteristic temperature is a medium value. When the temperature gradient is constant on the sample the arithmetic medium value of the local temperatures is the effective characteristic temperature different phenomena. 相似文献
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I. Kirschner A. C. Bódi R. Laiho E. Lähderanta 《Zeitschrift für Physik B Condensed Matter》1996,101(4):535-537
A new, dynamic procedure is elaborated to create vortex-glass state in high-T c superconductors, which consists of the application of the thermometric mapping method together with a thermal pulse. This results in the direct determination of main parameters of the given state, providing vortex-glass transition temperature of 88 K, correlation length of 2.1 mm, characteristic time of 15 s, moreover static and dynamic scaling exponents of 1.1 and 3.7, respectively. 相似文献
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I. Kirschner S. Leppävuori R. Laiho A. D. Caplin T. Karman E. Lähderanta G. Zsolt A. Uusimäki J. Laverty T. Porjesz I. Halasz J. Levoska Gy. Kovacs 《Zeitschrift für Physik B Condensed Matter》1990,78(3):381-387
It has been shown, that different starting materials result in Tl–Ca–Ba–Cu–O superconductors of different type even at the same heat treatment process. This manifests itself in the developing structure, in the number, share-rate and superconducting properties of the occurring phases as well. Microcrystals, phase-compositions, crystallinities, unit cells, onset and critical temperatures, magnetic flux exclusions, critical currents, magnetizations and critical magnetic fields essentially unlike from each other have been observed, depending on the starting materials. The presence of a starting compound having low melting point, as Ba(NO3)2 can cause a more compact, better superconducting final product, implying better connection between the grains. 相似文献