We report temperature- and magnetic-field-dependent measurements of the dc resistivity and the far-infrared reflectivity (FIR) (photon energies ω=50-700 cm-1) of superlattices comprising ten consecutive unit cells of the antiferromagnetic insulator CaMnO3, and four to ten unit cells of the correlated paramagnetic metal CaRuO3. Below the Néel temperature of CaMnO3, the dc resistivity exhibits a logarithmic divergence upon cooling, which is associated with a large negative, isotropic magnetoresistance. The ω→0 extrapolation of the resistivity extracted from the FIR reflectivity, on the other hand, shows a much weaker temperature and field dependence. We attribute this behavior to scattering of itinerant charge carriers in CaRuO3 from sparse, spatially isolated magnetic defects at the CaMnO3-CaRuO3 interfaces. This field-tunable "transport bottleneck" effect may prove useful for functional metal-oxide devices.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jul 7 2011|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics