Role of structure imperfection in the formation of the magnetotransport properties of rare-earth manganites with a perovskite structure
| Autor: | N.A. Liedienov, V. G. Pitsyuga, A. V. Pashchenko, V. K. Prokopenko, Georgiy Levchenko, Yu. F. Revenko, Anton S. Mazur, Vitalii Turchenko, V. Ya. Sycheva, V. P. Pashchenko |
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| Rok vydání: | 2017 |
| Předmět: |
010302 applied physics
Materials science Ionic radius Magnetoresistance Condensed matter physics General Physics and Astronomy 02 engineering and technology Crystal structure 021001 nanoscience & nanotechnology Magnetic hysteresis 01 natural sciences Electrical resistivity and conductivity Vacancy defect 0103 physical sciences 0210 nano-technology Phase diagram Perovskite (structure) |
| Zdroj: | Journal of Experimental and Theoretical Physics. 124:100-113 |
| ISSN: | 1090-6509 1063-7761 |
| DOI: | 10.1134/s1063776116150127 |
| Popis: | 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 R3c 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. |
| Databáze: | OpenAIRE |
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