Charge-ordering contribution to the magnetic entropy change of (Pr, Ca)MnO3 manganites


In the present work, we analyze the influence of the charge-ordering on the magnetic entropy change of Pr1-xCaxMnO3 manganites (0.20 < x < 0.95). The samples with x < 0.30 and x > 0.90 present the usual ferromagnetic and antiferromagnetic behavior, peaking at the Curie and Neel temperature, respectively. In contrast, for the samples with charge-ordering (0.30 < x < 0.90), a much smaller positive peak on the magnetic entropy change was observed around the charge-ordering temperature T-CO. This effect is associated to a negative contribution from the spin ordering Delta S-spin which is superimposed to a positive contribution due the charge-ordering Delta S-CO. We could also appraise Delta S-CO(max) as a function of Ca content (0.30 < x < 0.90), under 4 T of magnetic field change. Delta S-CO(max) vanishes for the limits x similar to 0.30 and similar to 0.90, and presents a deep minimum around x similar to 0.50, with two maxima at x similar to 0.35 and 0.65. (c) 2004 Elsevier B.V. All rights reserved.


Materials Science; Physics


Reis, MS; Gomes, AM; Araujo, JP; Amaral, JS; Tavares, PB; Oliveira, IS; Amaral, VS

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