Electric Dipolarization near the Metal-Insulator Transition in La(subscript 1−x)Sr(subscript x)MnO3

G. Chern ； Y. L. Liu ； M. F. Tai ； R. Gundakaram ； J. G. Lin

《Chinese Journal of Physics》 43卷4期 (2005/08) Pp. 867-873

並列摘要

The complex dielectric constants (ε' and ε'') of La(subscript 1−x)Sr(subscript x)MnO3 (x = 0, 0.05, 0.15) were measured as a function of frequency ν(20-10^6 Hz) and temperature (80-300 K). A ferroelectric-like dielectric constant ranging from 10^6 to 10^9 was obtained in both insulating LaMnO3 and metallic La(subscript 0.85)Sr(subscript 0.15)MnO3. The major effect of Sr doping was found to be the enhancement of the low frequency polarization and a decrease of the activation energy associated with the dipolar motion. At x = 0.15, the frequency dependent dielectric response shows a constant ε' (~10^7) and a 1/ν dependence of ε'', which reflects the nature of electric polarizability. Relative to the typical plasma frequency, the present results have shown that the response time of a small electric field can be much longer (microseconds to milliseconds) for La(subscript 1−x)Sr(subscript x)MnO3 near the metal-insulator transition, suggesting possible applications of electric-field-driven phase transition in these materials.