The crucial role of mixed valence in the magnetoresistance properties of manganites and cobaltites

The mixed valence Mn3+/Mn4+ and Co3+/Co4+ in manganites and cobaltites with the perovskite structure is absolutely necessary for the appearance of magnetotransport properties. It is shown that in these systems the Jahn Teller effect of the transition element, the charge and orbital ordering and the...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences physical, and engineering sciences, 2008-01, Vol.366 (1862), p.83-92
Main Author: Raveau, B
Format: Article
Language:English
Subjects:
Charge-Orbital Ordering
Cobalt
Colossal Magnetoresistance Manganites And Cobaltites
Competition Between Ferromagnetism And Antiferromagnetism Or Spin Glass
Crystallographic And Electronic Phase Separation
Doping
Electrical phases
Ferromagnetism
Jahn Teller Effect
Magnetic fields
Magnetization
Oxides
Oxygen
Perovskites
Spin glasses
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Summary:The mixed valence Mn3+/Mn4+ and Co3+/Co4+ in manganites and cobaltites with the perovskite structure is absolutely necessary for the appearance of magnetotransport properties. It is shown that in these systems the Jahn Teller effect of the transition element, the charge and orbital ordering and the oxygen stoichiometry play a key role in the appearance of large and even colossal magnetoresistance. It has been discovered that these oxides exhibit a new phenomenon, the crystallographic and electronic phase separation. It is this phenomenon that is at the origin of the competition between ferromagnetism and antiferromagnetism or spin glass behaviour and which leads to the negative magnetoresistance (MR). The doping of these materials at different sites appears then to be a means of inducing large MR effects.
ISSN:1364-503X
1471-2962
DOI:10.1098/rsta.2007.2141