Possible Long-Range Order with Singlet Ground State in CeRu2Al10

概要

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We investigate the thermal and transport properties of CexLa1-xRu2Al10 to clarify the origin of the recently discovered mysterious phase below $T_{0}=27$ K in CeRu2Al10 where a large magnetic entropy is released, however, the existence of an internal magnetic field is ruled out by 27Al-NQR measurement. We find that $T_{0}$ decreases with decreasing $x$ and disappears at $x\sim 0.45$. $T_{0}$ of CeRu2Al10 is suppressed down to 26 K under $H=14.5$ T along the $a$-axis. These results clearly indicate that the transition has a magnetic origin and is ascribed to the interaction between Ce ions. Considering the results of specific heat, magnetic susceptibility, thermal expansion, and electrical resistivity and also 27Al-NQR, we propose that the transition originates from the singlet pair formation between Ce ions. Although its properties in a Ce dilute region is basically understood by the impurity Kondo effect, CeRu2Al10 shows a Kondo-semiconductor-like behavior. The phase transition at $T_{0}$ may be characterized as a new type of phase transition that appears during the crossover from the dilute Kondo to the Kondo semiconductor.
Physical Society of Japanの論文
2010-04-15