| 1. |
- Demidov, V. V., et al.
(författare)
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Magnetic Anisotropy of Strained Epitaxial Manganite Films
- 2011
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Ingår i: Journal of Experimental and Theoretical Physics. - : Pleiades Publishing Ltd. - 1090-6509 .- 1063-7761. ; 112:5, s. 825-832
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Tidskriftsartikel (refereegranskat)abstract
- The in-plane magnetic anisotropy of epitaxial La(0.7)Sr(0.3)MnO(3) (LSMO) films is studied at room temperature by the following three independent techniques: magnetooptical Kerr effect, ferromagnetic resonance at a frequency of 9.61 GHz, and recording of absorption spectra of electromagnetic radiation at a frequency of 290.6 MHz. The films are deposited onto NdGaO(3) (NGO) substrates in which the (110) NGO plane is tilted at an angle of 0-25.7 degrees to the substrate plane. The uniaxial magnetic anisotropy induced by the strain of the film is found to increase with the tilt angle of the (110) NGO plane. A model is proposed to describe the change in the magnetic anisotropy energy with the tilt angle. A sharp increase in the radio-frequency absorption in a narrow angular range of a dc magnetic field near a hard magnetization axis is detected The anisotropy parameters of the LSMO films grown on (110) NGO, (001) SrTiO(3), and (001)[(LaAlO(3))(0.3) + (Sr(2)AlTaO(6))(0.7)] substrates are compared.
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| 2. |
- Dzhezherya, Yu. I., et al.
(författare)
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Kapitza problem for the magnetic moments of synthetic antiferromagnetic systems
- 2012
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 115:2, s. 284-288
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of magnetization in synthetic antiferromagnetic systems with the magnetic dipole coupling in a rapidly oscillating field has been examined. It has been revealed that the system can behave similar to the Kapitza pendulum. It has been shown that an alternating magnetic field can be efficiently used to control the magnetic state of a cell of a synthetic antiferromagnet. Analytical relations have been obtained between the parameters of such an antiferromagnet and an external magnetic field at which certain quasistationary states are implemented.
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| 3. |
- Dzhezherya, Yu I., et al.
(författare)
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Remagnetization of synthetic antiferromagnetic cells by a magnetic field pulse
- 2013
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 117:6, s. 1059-1065
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Tidskriftsartikel (refereegranskat)abstract
- The theory of the dynamic remagnetization of a synthetic antiferromagnetic system and magnetic points located on a magnetic substrate in an external magnetic field has been considered. The energies of the equilibrium states of the system have been calculated. The conditions of switching between equilibrium states have been described. The conditions of applicability of this theory have been formulated. It has been shown that the process of remagnetization can be implemented in an inertialess regime, escaping the long-term relaxation of the system to a new equilibrium position with the use of a special shape of the field signal. The possibility of the reduction of the switching field amplitude by varying the pulse duration has been demonstrated.
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| 4. |
- Gorbatov, O. I., et al.
(författare)
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Role of Magnetism in the Formation of a Short-Range Order in Iron-Silicon Alloys
- 2011
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 112:5, s. 848-859
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Tidskriftsartikel (refereegranskat)abstract
- The formation of a short-range order in soft magnetic Fe-Si alloys depending on the annealing temperature has been investigated theoretically and experimentally. The B2-type short-range order has been observed in samples quenched from temperatures T > T(C) (where T(C) is the Curie temperature) with the content c(Si) close to the boundary of the two-phase region. Annealing at temperatures T < T(C) for the content c(Si) >= 0.08 leads to an increase in the fraction of regions with the D0(3)-type short-range order. The mechanism of the formation of the short-range order in Fe-Si solid solutions has been analyzed by the Monte Carlo simulation with the ab initio calculated interatomic interaction parameters. It has been shown that the energy of the effective Si-Si interaction in bcc iron strongly depends on the magnetic state of the matrix. As a result, the B2-type short-range order is formed at T > T(C) and is fixed at quenching, whereas the D0(3)-type short-range order is equilibrium in the ferromagnetic state. The results reveal the decisive role of magnetism in the formation of the short-range order in Fe-Si alloys and allow the explanation of the observed structural features of the alloys depending on the composition and temperature.
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| 5. |
- Gorshunov, B. P., et al.
(författare)
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Subterahertz electrodynamics of (TMTSF)(2)X (X = ClO4, PF6) salts
- 2013
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 116:3, s. 460-466
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Tidskriftsartikel (refereegranskat)abstract
- The terahertz-subterahertz spectra of the complex permittivity and dynamic conductivity of polycrystalline (TMTSF)(2)ClO4 and (TMTSF)(2)PF6 samples are measured quantitatively. The spectra of (TMTSF)(2)ClO4 have absorption lines at frequencies of 7 and 30 cm(-1). The obtained temperature dependences of the line parameters in the range 5-300 K cast some doubt on the earlier concept of their phonon origin. An excitation is detected at temperatures below 20 K in the frequency range near 30 cm(-1), and its nature is related to the activation of a transverse acoustic phonon caused by the folding of the Brillouin zone due to the ordering of noncentrosymmetrical anions below 20 K. An increase in the carrier relaxation rate is found in this temperature range, which indicates a close relation between the electron and phonon subsystems in (TMTSF)(2)ClO4. Sings of additional low-energy excitations that should manifest themselves at frequencies below 1-2 cm(-1) are detected. (TMTSF)(2)PF6 containing centrosymmetrical anions has no absorption lines in the frequency range 3-20 cm(-1) and the temperature range 5-300 K.
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| 6. |
- Kamentsev, K. E., et al.
(författare)
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High-temperature structural phase transition in the LiCu2O2 multiferroic
- 2013
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 117:2, s. 320-326
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Tidskriftsartikel (refereegranskat)abstract
- The results of thermogravimetric, X-ray diffraction, and electrical studies of LiCu2O2 single crystals in the temperature range 300-1100 K are presented. A reversible first-order phase transition between the orthorhombic and tetragonal phases is found to occur in these single crystals at T = 993 K. A pronounced peak on a differential thermal analysis curve and jumps in the unit cell parameters and the electrical resistivity are detected at the phase-transition temperature. The data on the crystal structure of LiCu2O2 and the phase transition-induced change in the entropy determined in this work are used to conclude that the revealed phase transition is caused by the ordering-disordering of Li+ and Cu2+ cations in their structural positions.
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| 7. |
- Karelin, A. V., et al.
(författare)
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New measurements of the energy spectra of high-energy cosmic-ray protons and helium nuclei with the calorimeter in the PAMELA experiment
- 2014
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 119:3, s. 448-452
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Tidskriftsartikel (refereegranskat)abstract
- New measurements of the energy spectra of cosmic-ray protons and helium nuclei with significantly increased statistics owing to an improvement of the event selection technique and the involvement of all data over the period 2006-2013 in the analysis have been made at energies above 0.8 TeV/nucleon with a position-sensitive calorimeter based on data from the PAMELA satellite-borne experiment.
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| 8. |
- Karelin, A. V., et al.
(författare)
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North-south asymmetry for high-energy cosmic-ray electrons measured with the PAMELA experiment
- 2013
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 117:2, s. 268-273
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Tidskriftsartikel (refereegranskat)abstract
- The north-south asymmetry for cosmic-ray particles was measured with one instrument of the PAMELA satellite-borne experiment in the period June 2006-May 2009. The analysis has been performed by two independent methods: by comparing the count rates in regions with identical geomagnetic conditions and by comparing the experimental distribution of particle directions with the simulated distribution that would be in the case of an isotropic particle flux. The dependences of the asymmetry on energy release in the PAMELA calorimeter and on time have been constructed. The asymmetry (N (n) - N (s) )/(N (n) + N (s) ) is 0.06 +/- 0.004 at the threshold energy release in the calorimeter and gradually decreases with increasing energy release. The observed effect is shown to be produced by electrons in the energy range 10-100 GeV.
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| 9. |
- Liberman, M. A., et al.
(författare)
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On the mechanism of the deflagration-to-detonation transition in a hydrogen-oxygen mixture
- 2010
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 111:4, s. 684-698
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Tidskriftsartikel (refereegranskat)abstract
- The flame acceleration and the physical mechanism underlying the deflagration-to-detonation transition (DDT) have been studied experimentally, theoretically, and using a two-dimensional gasdynamic model for a hydrogen-oxygen gas mixture by taking into account the chain chemical reaction kinetics for eight components. A flame accelerating in a tube is shown to generate shock waves that are formed directly at the flame front just before DDT occurred, producing a layer of compressed gas adjacent to the flame front. A mixture with a density higher than that of the initial gas enters the flame front, is heated, and enters into reaction. As a result, a high-amplitude pressure peak is formed at the flame front. An increase in pressure and density at the leading edge of the flame front accelerates the chemical reaction, causing amplification of the compression wave and an exponentially rapid growth of the pressure peak, which "drags" the flame behind. A high-amplitude compression wave produces a strong shock immediately ahead of the reaction zone, generating a detonation wave. The theory and numerical simulations of the flame acceleration and the new physical mechanism of DDT are in complete agreement with the experimentally observed flame acceleration, shock formation, and DDT in a hydrogen-oxygen gas mixture.
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| 10. |
- Petrzhik, A. M., et al.
(författare)
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Electron transport in hybrid superconductor heterostructures with manganite interlayers
- 2011
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Ingår i: Journal of Experimental and Theoretical Physics. - : Pleiades Publishing Ltd. - 1090-6509 .- 1063-7761. ; 112:6, s. 1042-1050
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid herostructures comprising an YBa(2)Cu(3)O (x) (YBCO) high-temperature superconductor (HTS) layer and Nb/Au low-temperature superconductor (LTS) bilayer (with critical HTS and LTS temperatures T (c) and T'(c), respectively), separated by a thin (d (M) = 5-20 nm) interlayer of LaMnO(3), La(0.7)Ca(0.3)MnO(3), or La(0.7)Sr(0.3)MnO(3) manganite have been studied. The electric resistance and magnetic properties of individual (evaporated directly onto the substrate) manganite films and related hybrid herostructures have been measured. Based on quasi-classical equations, analytical expressions for the conductivity of herostructures at T a parts per thousand currency sign T'(c) are obtained in the case of a low-transparency superconductor/manganite interface. It is established that the conductivity of heterostructures is determined by the proximity effect (related to the penetration of a condensate wavefunction from the Nb/Au bilayer to manganite) and depends strongly on interface transparency. At low temperatures (T a parts per thousand(a) T (c)'), the conductivity peaks are found at voltages determined by the exchange field of the manganite interlayer. At T (c)'
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