Transport and Thermoelectric Properties of the Ca1−x Sr x Ru1−y Mn y O3 System

The magnetic, transport, and thermoelectric properties of Ca1−x Sr x Ru1−y Mn y O3 have been investigated. Ferromagnetism with relatively high T C (>200 K) was introduced by Mn doping. In particular, ferromagnetism appeared in the Ca0.5Sr0.5Ru1−y Mn y O3 system at y > 0.2. The maximum T C (=270 K) was recorded for a specimen of Ca0.5Sr0.5Ru0.4Mn0.6O3. The ferromagnetism seems to be due to the mixed-valence states of Mn3+, Mn4+, Ru4+, and Ru5+ ions. The metallic character of Ru-rich specimens was suppressed by Mn substitution, and the system was transformed into a semiconductor at relatively low Mn content near y = 0.1. Specimens with higher Mn content (y > 0.8) had large thermoelectric power (50 μV K−1 to 130 μV K−1 at 280 K) accompanied by relatively low resistivity (0.03 Ω cm to 1 Ω cm). The Ca0.5Sr0.5Ru1−y Mn y O3 system seems to have good potential as a thermoelectric material for use above 300 K.