We investigated the switching dynamics of two kinds of EuBa2Cu3Oy (Eu123) intrinsic Josephson junctions (IJJs) with different anisotropy parameters gamma (= (m*c/m*ab)1/2) tuned to 37 and 22. In contrast to weakly-coupled IJJs in Bi2212, significant deviations from the thermally activated escape model of a single-stack Josephson junction were observed in their switching current distributions, P(I), due to the strongly-coupled nature of the Eu123 IJJs, The P(I) of the two IJJs are found to be independent of temperature, below 1.4 K and 4.2 K, respectively; which indicates the observation of macroscopic quantum tunneling at high temperatures of liquid He.
@article{arxiv.0705.1651,
title = {Switching Current Measurements of EuBa2Cu3Oy Intrinsic Josephson Junctions},
author = {S. Ueda and T. Okutsu and S. Ishii and Y. Takano},
journal= {arXiv preprint arXiv:0705.1651},
year = {2007}
}