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Nuclear structure and magnetic properties of La1-xNdxFe0.5Cr0.5O3
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
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(English)Manuscript (Other (popular science, discussion, etc.))
URN: urn:nbn:se:uu:diva-92728OAI: oai:DiVA.org:uu-92728DiVA: diva2:165909
Available from: 2005-03-17 Created: 2005-03-17 Last updated: 2013-03-21
In thesis
1. Synthesis, Nuclear Structure, and Magnetic Properties of some Perovskite Oxides
Open this publication in new window or tab >>Synthesis, Nuclear Structure, and Magnetic Properties of some Perovskite Oxides
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Synthesis, nuclear structure, and magnetic properties of the perovskites: Nd0.7-xMgxSr0.3MnO3 (x=0.0, 0.1), Nd0.6Mg0.1Sr0.3Mn1-zMgzO3 (z=0.1, 0.2), LaCr1-yMnyO3 (y=0.0, 0.1, 0.2, 0.3) and La1-xNdxFe0.5Cr0.5O3 (x=0.1, 0.15, 0.2) have been studied. The structure of the samples was investigated by X-ray and Neutron powder diffraction and the magnetic properties were investigated by magnetization measurements using SQUID-magnetometry. All compounds have orthorhombic structure with spacegroup Pnma (No. 62).

The compounds which had the composition Nd0.7Sr0.3Mn1-yMgyO3 by preparation, were found to attain the composition Nd0.7-xMgxSr0.3MnO3 and Nd0.6Mg0.1Sr0.3Mn1-zMgzO3. The x=0.0 and 0.1 compounds order in a pure ferromagnetic structure at about 200 K, but the Mn moments become slightly tilted and attain an antiferromagnetic component below 20 K. A ferromagnetic Nd moment also appears at low temperatures. The compounds with Mg substitution y=0.2 and 0.3 do not exhibit long range magnetic order, but local ferromagnetic correlations among the Mn moments appear below 200 K. At low temperature, also a local antiferromagnetic ordering of the Nd magnetic moments occurs. In these compounds, the Mn3+/Mn4+ ratio is reduced so that the double exchange interaction is suppressed and the antiferromagnetic superexchange interaction favoured.

The samples of composition LaCr1-yMnyO3 have orthorhombic structure at room temperature and below. The magnetic properties of the system are markedly affected by Mn-substitution. The parent compound LaCrO3 is a pure G-type antiferromagnet with Néel temperature 290 K. With incresing Mn-substitution, a ferromagnetic component developes in the ordered phase bcause of canting of the magnetic moments. The degree of canting increases with increasing Mn-substitution and the magnitude of the antiferromagnetic component of the moment decreases. The system La1-xNdxFe0.5Cr0.5O3 has the same antiferromagnetic G-type structure as LaCrO3, but orders already at temperatures above 400 K and develops only a very weak ferromagnetic component of the magnetic moment at low temperatures.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 50 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 24
Materials science, Magnetic Perovskites, Neutron powder diffraction, SQUID, Synthesis, Nuclear structure, Antiferromagnetism, Ferromagnetism, Superexchange, Double exchange, Colossal magnetoresistance, Materialvetenskap
National Category
Materials Engineering
urn:nbn:se:uu:diva-4826 (URN)91-554-6175-1 (ISBN)
Public defence
2005-04-07, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Available from: 2005-03-17 Created: 2005-03-17 Last updated: 2009-03-27Bibliographically approved

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