Replacing U for Ca in semiconducting CaB6 at the few at.% level induces metallic behaviour and Kondo-type phenomena at low temperatures, a rather unusual feature for U impurities in metallic hosts. For Ca0.992U0.008B6, the resistance minimum occurs at T = 17 K. The subsequent characteristic logarithmic increase of the resistivity with decreasing temperature merges into the expected T2 dependence below 0.8 K. Data of the low-temperature specific heat and the magnetization are analyzed by employing a simple resonance-level model. Analogous measurements on LaB6 with a small amount of U revealed no traces of Kondo behavior, above 0.4 K.
@article{arxiv.cond-mat/0407158,
title = {Kondo Behavior of U in CaB$_6$},
author = {G. A. Wigger and E. Felder and S. Weyeneth and H. R. Ott and Z. Fisk},
journal= {arXiv preprint arXiv:cond-mat/0407158},
year = {2009}
}
Comments
4 pages, 4 figures, submitted for publication to Europhysics Letters