  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.
