Lu-induced spin entropy enhancement in Ca_3Co_4O _9+δ system

摘要

The magnetothermopower have been studied in Lu-doped Ca _(3-x)Lu_xCo_4O_(9+δ). A strong magnetic field suppression of thermopower indicates large spin entropy contribution. The magnetothermopower for doped samples are overall enhanced compared with that for undoped Ca_3Co_4O _(9+δ), providing an experimental evidence for the enhancement of spin entropy. Magnetic results confirm that Co~(4+) concentration is reduced by Lu doping. We suggest that the reduction in Co~(4+) concentration results in the enhanced spin entropy.