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A. V. Pashchenko V. P. Pashchenko Yu. F. Revenko V. K. Prokopenko A. S. Mazur V. A. Turchenko V. V. Burkhovetskii A. G. Sil’cheva P. P. Konstantinov Yu. M. Gufan 《Physics of the Solid State》2013,55(2):321-325
The structural, resistive, magnetic, and magnetoresistive properties of the La0.6Sr0.3 ? x Bi x Mn1.1O3 ceramics have been studied. The substitution of Bi ions for Sr ions increases the lattice parameter of the rhombohedral perovskite structure, decreases the metal-semiconductor and ferromagnet-paramagnet phase transition temperatures and the peak of the magnetoresistive effect, and increases the resistivity, approaching the system to the ferroelectric state. The 55Mn NVR study indicates on the high-frequency Mn3+ ? Mn4+ superexchange and heterogeneity of the valence and magnetic states of manganese due to the nonuniformity of distribution of all ions and defects. The phase diagram has been constructed, which shows a strong correlation between the structural, magnetic, and magnetoresistive properties. 相似文献
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A. V. Pashchenko V. P. Pashchenko V. K. Prokopenko V. A. Turchenko Yu. F. Revenko A. S. Mazur V. Ya. Sycheva N. A. Liedienov V. G. Pitsyuga G. G. Levchenko 《Journal of Experimental and Theoretical Physics》2017,124(1):100-113
The structure, the structure imperfection, and the magnetoresistance, magnetotransport, and microstructure properties of rare-earth perovskite La0.3Ln0.3Sr0.3Mn1.1O3–δ manganites are studied by X-ray diffraction, thermogravimetry, electrical resistivity measurement, magnetic, 55Mn NMR, magnetoresistance measurement, and scanning electron microscopy. It is found that the structure imperfection increases, and the symmetry of a rhombohedrally distorted R3?c perovskite structure changes into its pseudocubic type during isovalent substitution for Ln = La3+, Pr3+, Nd3+, Sm3+, or Eu3+ when the ionic radius of an A cation decreases. Defect molar formulas are determined for a real perovskite structure, which contains anion and cation vacancies. The decrease in the temperatures of the metal–semiconductor (T ms) and ferromagnet–paramagnet (T C) phase transitions and the increase in electrical resistivity ρ and activation energy E a with increasing serial number of Ln are caused by an increase in the concentration of vacancy point defects, which weaken the double exchange 3d 4(Mn3+)–2p 6(O2–)–3d 3(Mn4+)–V (a)–3d 4(Mn3+). The crystal structure of the compositions with Ln = La contains nanostructured planar clusters, which induce an anomalous magnetic hysteresis at T = 77 K. Broad and asymmetric 55Mn NMR spectra support the high-frequency electronic double exchange Mn3+(3d 4) ? O2–(2p 6) ? Mn4+(3d 3) and indicate a heterogeneous surrounding of manganese by other ions and vacancies. A correlation is revealed between the tunneling magnetoresistance effect and the crystallite size. A composition–structure imperfection–property experimental phase diagram is plotted. This diagram supports the conclusion about a strong influence of structure imperfection on the formation of the magnetic, magnetotransport, and magnetoresistance properties of rare-earth perovskite manganites. 相似文献
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Kostishin V. G. Korovushkin V. V. Isaev I. M. Mironovich A. Yu. Trukhanov S. V. Turchenko V. A. Astapovich K. A. Trukhanov A. V. 《Physics of the Solid State》2021,63(2):253-260
Physics of the Solid State - Using Mössbauer spectroscopy, magnetometry and X-ray diffraction, we have studied the BaYxFe12 – xO19 hexaferrite (0.1 ≤ x ≤... 相似文献
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A. V. Pashchenko V. P. Pashchenko V. K. Prokopenko Yu. F. Revenko A. S. Mazur V. A. Turchenko V. Ya. Sycheva V. V. Burkhovetskii A. G. Sil’cheva G. G. Levchenko 《Physics of the Solid State》2013,55(3):486-494
Ceramic samples of manganite perovskites La0.6 ? x Pr x Sr0.3Mn1.1O3 (x = 0?0.6) have been studied using the X-ray diffraction, resistive, magnetic (χac, 55Mn NMR), microscopic, and magnetoresistive methods. It has been found that an increase in the praseodymium concentration x leads to a transition from the rhombohedral R $\bar 3$ c (x = 0–0.3) to orthorhombic Pbnm (x = 0.4–0.6) perovskite structure. It has been shown that the real perovskite structure contains anion and cation vacancies, whose concentrations increase with an increase in the praseodymium concentration x. A decrease in the metal-insulator phase transition temperature T mi and the ferromagnetic-paramagnetic phase transition temperature T c with increasing x correlates with an increase in the concentration of vacancies weakening the high-frequency electronic exchange Mn3+ ? Mn4+. For compositions with x = 0 and 0.1, when the lattice contains not only vacancies but also nanostructured clusters with Mn2+ in the A-positions, there is an anomalous hysteresis. An analysis of the asymmetrically broadened 55Mn NMR spectra of the compounds has revealed a high-frequency electronic exchange of the ions Mn3+ Mn4+ in the B-positions and a local heterogeneity of their surrounding by other ions (La2+, Pr3+, Sr2+) and vacancies. The phase diagram has demonstrated that there is a strong correlation between the composition, imperfection of the perovskite structure, phase transition temperatures T mi and T c , and magnetoresistive properties. 相似文献
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Alex Trukhanov Larisa Panina Sergei Trukhanov Vitalii Turchenko Mohamed Salem 《中国物理 B》2016,25(1):16102-016102
The investigations of the crystal and magnetic structures of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been performed with powder neutron diffractometry. Magnetic properties of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been measured by vibration sample magnetometry at different temperatures under different magnetic fields.The atomic coordinates and lattice parameters have been Rietveld refined. The invar effect is observed in low temperature range(from 4.2 K to 150 K). It is explained by the thermal oscillation anharmonicity of atoms. The increase of microstress with decreasing temperature is found from Rietveld refinement. The Curie temperature and the change of total magnetic moment per formula unit are found for all compositions of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions. The magnetic structure model is proposed. The most likely reasons and the mechanism of magnetic structure formation are discussed. 相似文献
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V. P. D’yakonov V. P. Pashchenko É. E. Zubov V. I. Mikhailov Yu. Bukhantsev I. M. Fita V. A. Turchenko N. A. Doroshenko A. Szevczik R. Zuberek G. Szymczak 《Physics of the Solid State》2003,45(5):914-921
The magnetic and transport properties of La1?x Mn1+x O3 manganites with excess manganese are studied. It is shown that magnetic and charge ordering heavily depends on the superstoichiometric manganese content, magnetic field, and pressure. The magnetoresistive effect (MRE) is enhanced as the manganese concentration increases. In addition to the paramagnet-ferromagnet transition, the temperature dependences of the magnetization exhibit anomalies at low temperatures in samples with x=0.1–0.4. The magnetization decreases at T<45 K in fields H<0.2 kOe and increases as H changes from 0.2 to 10 kOe. An analysis shows that the features observed at low temperatures are most probably related to the transition from the ferromagnetic state to the canted spin structure in clusters of mixed-valence manganese ions. The temperature dependences of the magnetization and resistivity remain unchanged as the pressure increases. It is demonstrated that the Curie and metal-dielectric transition temperatures shift to higher values as the manganese concentration increases under pressure. The temperature of the MRE peak increases under pressure, while the MRE decreases. 相似文献
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V. P. Pashchenko Yu. F. Revenko A. V. Pashchenko V. K. Prokopenko A. A. Shemyakov V. A. Turchenko N. I. Nosanov V. I. Volkov V. M. Ishchuk I. N. Chukanova A. I. Bazhin V. V. Pashchenko 《Technical Physics》2005,50(11):1497-1503
Magnetoresistive ceramic and thick-and thin-film La0.6Sr0.3Mn1.1?x Fe x O3±δ(x=0,0.04) samples are studied by X-ray diffraction, 55Mn nuclear magnetic resonance (NMR), resistivity measurements, and magnetic measurements. Their rhombohedrally distorted ( $R\overline 3 c$ ) perovskite structure is found to contain anion and cation vacancies and nanocluster defects. Their broad asymmetric 55Mn NMR spectra support high-frequency electron-hole exchange between Mn3+ and Mn4+ and the fact that their environments are different due to a high defect concentration and high structural inhomogeneity. Iron doping and an increase in the annealing temperature result in a decrease in the temperatures of the metal-semiconductor and ferromagnet-paramagnet phase transitions and an increase in the magnetoresistive effect (MRE). The low-field MRE in the low-temperature region (~100 K) in the ceramics and thick film is explained by tunneling in crystallite boundaries. An analysis of the effect of iron and the annealing temperature on the activation energy confirms the conclusion regarding a defect system of the perovskite structure and the presence of several mechanisms of activation processes. 相似文献
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A. V. Trukhanov V. G. Kostishin V. V. Korovushkin L. V. Panina S. V. Trukhanov V. A. Turchenko I. S. Polyakov R. Kh. Rakhmatullin G. A. Filatov T. I. Zubar’ V. V. Oleinik E. S. Yakovenko L. Yu. Matsui L. L. Vovchenko V. L. Launets E. L. Trukhanova 《Physics of the Solid State》2018,60(9):1768-1777
The correlation of the chemical composition, the structure, and the microwave characteristic of solid solutions of the BaFe12 – xDxO19 (0.1 ≤ x ≤ 1.2) barium hexaferrite substituted with diamagnetic Al3+ and In3+ ions has been studied. The precise data on the crystal structure have been obtained by powder neutron diffraction using a high-resolution Fourier diffractometer (Dubna, JINR). The data on the distribution of the diamagnetic substituting ions in the hexaferrite structure have been obtained by Mössbauer spectroscopy. The microwave properties (the transmittance and the reflectance) have been studied in the frequency range 20–65 GHz and in external magnetic fields to 8 kOe. It is found that the transmission spectra are characterized by a peak that corresponds to the resonant frequency of the electromagnetic energy absorption, which is due to the ferromagnetic resonance phenomenon. The correlation of the chemical composition, the features of the ion distribution in the structure, and the electromagnetic properties has been revealed. It is shown that external magnetic fields shift the absorption peak of electromagnetic radiation to higher frequencies due to an increase in the magnetocrystal anisotropy. The results enable the conclusion that the features of the intrasublattice interactions and the electromagnetic properties should be explained using the phenomenological Goodenough–Kanamori model. 相似文献
10.
A. V. Pashchenko A. A. Shemyakov V. P. Pashchenko V. A. Turchenko V. K. Prokopenko Yu. F. Revenko Yu. V. Medvedev B. M. éfros G. G. Levchenko 《Physics of the Solid State》2009,51(6):1193-1203
Magnetoresistive ceramic samples La0.7Ca0.3 − x
Sr
x
MnO3 ± δ sintered at temperatures of 1150 and 1350°C are investigated using X-ray diffraction, microscopic, resistance, and magnetic
(χ, 55Mn NMR) measurements. The specific features of the influence of the composition on the type and parameters of the perovskite
structure, its imperfection, the porous crystallite structure, the metal-semiconductor and ferromagnetic-paramagnetic phase
transitions, the 55Mn NMR spectra, and the magnetoresistance effect are established. The magnetic phase diagram is constructed. The conclusions
are drawn regarding the nonuniformity of the distribution of ions and vacancies around manganese involved in the high-frequency
electron-hole exchange (Mn3+ ai Mn4+) and the nanostructured separation of the perovskite structure containing anion and cation vacancies, with the concentrations
and magnetoresistance effect decreasing and the lattice parameters and phase transition temperatures increasing as calcium
is replaced by strontium.
Original Russian Text ? A.V. Pashchenko, A.A. Shemyakov, V.P. Pashchenko, V.A. Turchenko, V.K. Prokopenko, Yu.F. Revenko,
Yu.V. Medvedev, B.M. éfros, G.G. Levchenko, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 6, pp. 1127–1136. 相似文献