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Medientyp:
E-Artikel
Titel:
The Crucial Role of Mixed Valence in the Magnetoresistance Properties of Manganites and Cobaltites
Beteiligte:
Raveau, B.
Erschienen:
The Royal Society, 2008
Erschienen in:
Philosophical Transactions: Mathematical, Physical and Engineering Sciences, 366 (2008) 1862, Seite 83-92
Sprache:
Englisch
ISSN:
1364-503X
Entstehung:
Anmerkungen:
Beschreibung:
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.