SwePub - sökning: WFRF:(Savosta M. M.)

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1.	Pashchenko, V. P., et al. (författare) Structural and magnetic inhomogeneity and the NMR of Mn-55 and La-139 in the magnetoresistive ceramics La0.7Ba0.3-xSnxMnO3 -> La0.7-xBa0.3-xMnO3+0.5xLa(2)Sn(2)O(7) 2003 Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 29:11, s. 910-916 Tidskriftsartikel (refereegranskat)abstract The effects of substitution of barium by tin on the phase composition, structural imperfection, and properties of lanthanum manganite perovskites La0.7Ba0.3-xSnxMnO3 (X=0, 0.1, 0.15, 0.2, 0.3) are established by comprehensive studies done by x-ray diffraction, resistive, and magnetic (including NMR on Mn-55 and La-139) methods. It is shown that the introduction of Sn leads to the formation of a pyrochloric phase La2Sn2O7, to an increase in the density of lattice defects of the manganese-enriched main lanthanum manganite phase, and to a substantial decrease of the magnetoresistive effect. The smearing of the metal-semiconductor phase transition temperature is explained by an increase in the inhomogeneity and imperfection of the perovskite structure. The low activation energy is confirmed by a high degree of inhomogeneity and imperfection of the crystal lattice of the samples studied. The broad, asymmetric NMR spectra of Mn-55 and La-139 attest to high-frequency electron exchange between Mn3+ and Mn4+ and nonequivalence of the environment of those ions and La3+ due both to heterovalent ions and to vacancies and clusters.

Pashchenko, V. P., et al. (författare)
Structural and magnetic inhomogeneity and the NMR of Mn-55 and La-139 in the magnetoresistive ceramics La0.7Ba0.3-xSnxMnO3 -> La0.7-xBa0.3-xMnO3+0.5xLa(2)Sn(2)O(7)
2003
Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 29:11, s. 910-916
Tidskriftsartikel (refereegranskat)abstract
- The effects of substitution of barium by tin on the phase composition, structural imperfection, and properties of lanthanum manganite perovskites La0.7Ba0.3-xSnxMnO3 (X=0, 0.1, 0.15, 0.2, 0.3) are established by comprehensive studies done by x-ray diffraction, resistive, and magnetic (including NMR on Mn-55 and La-139) methods. It is shown that the introduction of Sn leads to the formation of a pyrochloric phase La2Sn2O7, to an increase in the density of lattice defects of the manganese-enriched main lanthanum manganite phase, and to a substantial decrease of the magnetoresistive effect. The smearing of the metal-semiconductor phase transition temperature is explained by an increase in the inhomogeneity and imperfection of the perovskite structure. The low activation energy is confirmed by a high degree of inhomogeneity and imperfection of the crystal lattice of the samples studied. The broad, asymmetric NMR spectra of Mn-55 and La-139 attest to high-frequency electron exchange between Mn3+ and Mn4+ and nonequivalence of the environment of those ions and La3+ due both to heterovalent ions and to vacancies and clusters.

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