https://doi.org/10.1140/epjb/e2002-00386-3
Preparation, magnetoresistance and magnetocaloric effect of two-layered perovskite La2.5-xK0.5+xMn2O7+δ
1
National Laboratory of Solid State Microstructures, Nanjing University,
Nanjing 210093, PR China
2
Department of Physics, Heibei Normal University,
Shijiazhuang 050091, PR China
3
Chemistry Department and Center for Surface Analysis and Research,
Hong Kong Baptist University, Kowloon Tong, PR China
Corresponding author: a wzhong@ufp.nju.edu.cn
Received:
2
May
2002
Revised:
1
October
2002
Published online:
19
December
2002
Polycrystalline two-layered perovskite La2.5-xK0.5+xMn2O7+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 () and the
magnetic transition temperature (TC) is observed. Large magnetoresistance (MR) effects with
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 (
). The large
magnetic entropy change (~1.4 J/kg.K) is obtained in the sample La2.5-xK0.5+xMn2O7+δ (x = 0.35) upon 10 kOe applied magnetic field.
PACS: 75.30.Sg – Magnetocaloric effect, magnetic cooling / 82.80.-d – Chemical analysis and related physical methods of analysis / 81.05.Mh – Cermets, ceramic and refractory composites
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002