Eur. Phys. J. B 26, 467-471 (2002)
https://doi.org/10.1140/epjb/e20020115

Transport properties of La_1-xCa_xMnO₃ (0.5 ≤ x < 1)

Structure Research Laboratory, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, PR China

Corresponding author: ^a lixg@ustc.edu.cn

Received: 4 January 2002
Revised: 28 January 2002
Published online: 15 April 2002

Abstract

The transport properties of the La_1-xCa_xMnO₃ (0.5 ≤ x < 1) system in magnetic fields up to 14 T were studied. We found that the relationship between the charge ordering temperature T_CO and Mn⁴⁺ content obeys the formula , here n₀ and a are constants and T_max is the maximum of T_CO. For x=0.65, T_CO arrives at the maximum value of 249.5 K in zero magnetic field, while the charge ordered (CO) state is most stable around x = 0.75. For x = 0.5 when H < 6 T the resistivity displays Mott's variable-range hopping (VRH) behavior, when 6 < H < 12 T it is suggested that two kinds of conduction mechanism, i.e., VRH and magnetic polarons, coexist in the material, and when H > 12 T the resistivity shows metallic-like behavior and the transport mechanism is attributed to coexistence of magnetic polarons and free carriers. For x = 0.95, the conduction mechanism accords with the coexistence of VRH and magnetic polarons.