Measurements of the low-frequency (f≤100 kHz) permittivity (ε) and conductivity (σ) at T≲150 K are reported for La1-xCa xMnO3 (0≤x≤1) and Ca1-ySr yMnO3 (0≤y≤0.75) having antiferromagnetic, insulating ground states covering a broad range of Mn valencies from Mn 3+ to Mn4+. Static dielectric constants are determined from the low-T limiting behavior. With increasing T, relaxation peaks associated with charge-carrier hopping are observed in the real part of the permittivities and analyzed to determine dopant binding energies. The data are consistent with a simple model of hydrogenic impurity levels and imply effective masses m*/me∼3 for the Mn4+ compounds. Particularly interesting is a large dielectric constant (ε0∼100) associated with the C-type antiferromagnetic state near the composition La 0.2Ca0.8MnO3.
|Original language||English (US)|
|Number of pages||6|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Dec 2004|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics