We synthesized ACu3Ru4O12 (A = Na, Na0.5Ca0.5, Ca, Ca0.5La0.5, La) and measured their DC magnetization, AC susceptibility, specific heat, and resistivity, in order to investigate the effects of the hetero-valent substitution. A broad peak in the DC magnetization around 200 K was observed only in CaCu3Ru4O12, suggesting the Kondo effect due to localized Cu2+ ions. However, the electronic specific heat coefficients exhibit large values not only for CaCu3Ru4O12 but also for all the other samples. Moreover, the Wilson ratio and the Kadowaki-Woods ratio of our samples are all similar to the values of other heavy-fermion compounds. These results question the Kondo effect as the dominant origin of the mass enhancement, and rather indicate the importance of correlations among itinerant Ru electrons.
@article{arxiv.0811.4344,
title = {Heavy-Mass Behavior of Ordered Perovskites ACu3Ru4O12 (A = Na, Ca, La)},
author = {Soutarou Tanaka and Nobuhiro Shimazui and Hiroshi Takatsu and Shingo Yonezawa and Yoshiteru Maeno},
journal= {arXiv preprint arXiv:0811.4344},
year = {2009}
}
Comments
6 pages, 6 figures, to be published in J. Phys. Soc. Jpn