Spin entropy enhancement tuned by spin state transition in La0.7−xYxCa0.3CoO3

The effect of spin states on the spin entropy has been studied in La0.7−xYxCa0.3CoO3 (x=0.0, 0.05, 0.1 and 0.15). Magnetothermopower results reveal that Y-doping improves the spin entropy of La0.7Ca0.3CoO3. The magnetic results indicate that the Co3+ ions undergo a transition from an intermediate spin state (t52ge1g; S=1) to a low spin state (t62ge0g; S=0), which results in the enhancement of the spin entropy. A suitable theoretical model is suggested to explain well the enhancement of the spin entropy induced by spin state transition. This investigation gives strong evidence that the enhanced spin entropy contribution to the thermopower is tuned by the spin state transition.