Thermoelectric Power Anomaly of PrTi

概要

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We investigated thermoelectric properties for PrTi<inf>2</inf>Al<inf>20</inf>and PrV<inf>2</inf>Al<inf>20</inf>below room temperature down to 0.13 K. A clear positive peak has been observed at 75 K in the thermoelectric power S for PrTi<inf>2</inf>Al<inf>20</inf>. Also for PrV<inf>2</inf>Al<inf>20</inf>, the similar S peak has been detected at 40 K. These peaks arise from the Kondo effect in the magnetic excited levels of the 4f-electronic state under a cubic crystalline electric field (CEF). In addition, for PrTi<inf>2</inf>Al<inf>20</inf>, S takes a minimum with a negative sign at 10 K owing to the CEF effect, and shows an additional tiny negative hump below 2 K as a signature of quadrupole ordering. On the other hand, S for PrV<inf>2</inf>Al<inf>20</inf>manifests a large negative peak at 3 K with the magnitude of 3 μV/K. This gives a large enhancement in absolute S divided by temperature T, |S|/T, approximately below 10 K on cooling. |S|/T reaches 4 μV/K<sup>2</sup>at 0.2 K, which is larger than that in the zero-T limit for a heavy-electron compound CeRu<inf>2</inf>Si<inf>2</inf>. This observation strongly indicates that the heavy-electron state brought by the quadrupolar Kondo effect is realized in the non-Kramers \Gamma_{3} ground state of PrV<inf>2</inf>Al<inf>20</inf>.
2013-07-15