Polycrystalline two-layered perovskite La2.5-xK0.5+xMn2O 7 + δ (0 < x < 0.5) samples have been prepared by a modified sol-gel method and their magnetoresistance and magnetocaloric effects have been
studied. A large deviation between the metal-insulator (MI) transition temperature (Tρ) and the magnetic transition temperature (TC) is observed. Large magnetoresistance (MR) effects with Δρ/ρ of ∼40% at 12 kOe are obtained in wide temperature ranges. The maximum of the magnetic entropy change peaks at its Curie temperature
(TC), far above its MI transition temperature (Tρ). The large magnetic entropy change (∼1.4 J/kg.K) is obtained in the sample La2.5-xK0.5+xMn2O 7 + δ (x = 0.35) upon 10 kOe applied magnetic field.
Received 2 May 2002 / Received in final form 1st October 2002 Published online 19 December 2002
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ID="a"e-mail: wzhong@ufp.nju.edu.cn 相似文献
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