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Transport properties of Ce-doped =La, Pr, and Nd) manganites
P. Mandal,
Published in
Volume: 56
Issue: 23
Pages: 15073 - 15080
In Ce-doped (Formula presented) the rare earth (Formula presented) is partially replaced with cerium ions instead of divalent alkaline-earth metals. These compounds are very sensitive to annealing. The resistivity and thermoelectric power (TEP, (Formula presented) of (Formula presented) ((Formula presented)=La, Pr, and Nd) have been studied as a function of annealing conditions. They show a ferromagnetic to paramagnetic transition, and a resistive peak near (Formula presented) marking a metal-insulator (MI) transition. A pronounced giant magnetoresistance effect is also observed in these compounds, and (Formula presented) can be changed by annealing in various atmospheres. The (Formula presented) curve of oxygen overdoped samples shows double peaks along with a hysteresis loop (in the heating and cooling cycles), which bears the signature of the first-order nature of the transition. The thermopower of as-prepared samples show a peak near the MI transition, and changes sign from positive to negative at temperatures below the ferromagnetic transition. The magnitude of (Formula presented) at low temperatures is enhanced to an abnormally large value. With increasing of oxygen content, several characteristic features develop in the temperature dependence of the thermopower which is consistent with the resistive behavior. At high temperatures, the resistivity and thermopower follow the predictions of the Emin-Holstein theory of adiabatic polaron hopping. © 1997 The American Physical Society.
About the journal
JournalPhysical Review B - Condensed Matter and Materials Physics