Thermopower of Ce_xR<1-x>B_6(R=La, Pr and Nd)(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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The thermopower, S, of Ce_xR_<1-x>B_6 (R=La, Pr, Nd) was investigated. S with a positive sign shows a typical behavior observed in the Ce Kondo system, an increase with decreasing temperature at high temperatures and a maximum at low temperatures. The S values of all the systems at high temperatures are roughly linearly dependent on the Ce concentration, indicating the conservation of the singleimpurity character of the Kondo effect in a wide x range. However, the maximum value of S, S_<max>, and the temperature, T_<max>, at which S_<max> is observed exhibit different x dependences between Ce_xLa_<1_x>B_6 and Ce_xR_<1-x>B_6 (R=Pr, Nd). In Ce_xLa_<1-x>B_6, T_<max>, which is〜8K in CeB_6, decreases with decreasing x and converges to〜1K in a very dilute alloy and S_<max> shows an increase below x〜0.1 after decreasing with decreasing x. In Ce_xR_<1-x>B_6 (R=Pr, Nd), T_<max> shows a weak x dependence but S_<max> shows a roughly linear decrease in x. These results are discussed from the standpoint of the chemical pressure effect and the Ce-Ce interaction. S in the long-range ordered phase shows very different behaviors between Ce_xPr_<1-x>B_6 and Ce_xNd_<1-x>B_6.
社団法人日本物理学会の論文
2006-06-15