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Enhancement of the CMR Effect Near Room Temperature by Defects and Structural Transitions in La1−x−yCaxSryMnO3

Published online by Cambridge University Press:  10 February 2011

S. Kolesnik ,
B. Dabrowski ,
Z. Bukowski  and
J. Mais
S. Kolesnik
Affiliation:
Department of Physics, Northern Illinois University, DeKalb, IL 60115
B. Dabrowski
Affiliation:
Department of Physics, Northern Illinois University, DeKalb, IL 60115
Z. Bukowski
Affiliation:
Department of Physics, Northern Illinois University, DeKalb, IL 60115
J. Mais
Affiliation:
Department of Physics, Northern Illinois University, DeKalb, IL 60115
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Abstract

We have studied magnetoresistance of a series of La1−xSrxMnO3 and La1−x−yCaxSryMnO3 samples, for which structural and ferromagnetic transformation temperatures are in close proximity. On cooling in zero magnetic field, we observe a rapid increase of resistivity just above TC for La1−xSrxMnO3 samples with x < 0.1425 and x ≤ 0.1725 due to the O*-O' and R-O* - structural phase transformations, respectively. This increase is followed by a rapid decrease due to the ferromagnetic transition. The applied magnetic field significantly shifts the ferromagnetic transition to higher temperatures and suppresses the structure-related resistivity increase. We show that a combination of structural and ferromagnetic transitions gives rise to an enhancement of the negative magnetoresistance due to strong spin-lattice coupling. By choosing a proper composition, the enhancement can be optimized to appear in relatively low magnetic fields. A proper selection of Sr and Ca contents in La1−x−yCaxSryMnO3 and preparation conditions leads to an enhancement of the magnetoresistance effect at room temperature.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 602: Symposium JJ – Magnetoresistive Oxides & Related Materials , 1999 , 333
Copyright
Copyright © Materials Research Society 2000

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