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 (English)In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, Vol. 29, no 11, 910-916 p.Article in journal (Refereed) Published
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.
Place, publisher, year, edition, pages
2003. Vol. 29, no 11, 910-916 p.
electronic phase-separation, colossal magnetoresistance, transport-properties, manganites, transition, temperature, systems, crystal, oxides, size
IdentifiersURN: urn:nbn:se:kth:diva-23035ISI: 000187419600005OAI: oai:DiVA.org:kth-23035DiVA: diva2:341733
QC 201005252010-08-102010-08-10Bibliographically approved