spin state control of the perovskite rhco oxides自旋状态控制钙钛矿rhco氧化物.pdf

Materials 2010, 3, 786-799; doi:10.3390/ma3020786 OPEN ACCESS materials ISSN 1996-1944 /journal/materials Article Spin State Control of the Perovskite Rh/Co Oxides Ichiro Terasaki 1,, Soichiro Shibasaki 1, Shin Yoshida 1 and Wataru Kobayashi 2 1 Department of Applied Physics, Waseda University, Tokyo 169-8555, Japan 2 Waseda Institute for Advanced Study, Waseda University, Tokyo 169-8050, Japan Author to whom correspondence should be addressed; E-Mail: terra@waseda.jp; Tel./Fax.: +81-3-5286-3854. Received: 30 December 2009; in revised form: 23 January 2010 / Accepted: 26 January 2010 / Published: 27 January 2010 Abstract: We show why and how the spin state of transition-metal ions affects the thermoelectric properties of transition-metal oxides by investigating two perovskite-related oxides. In the A-site ordered cobalt oxide Sr YCo O , partial substitution of Ca for 3 4 10.5 Sr acts as chemical pressure, which compresses the unit cell volume to drive the spin state crossover, and concomitantly changes the magnetization and thermopower. In the perovskite rhodium oxide LaRhO , partial substitution of Sr for La acts as hole-doping, 3 and the resistivity and thermopower decrease systematically with the Sr concentration. The thermopower remains large values at high temperatures (150 µV/K at 800 K), which mak