The acoustic characteristics for high damping Mn73Cu20Ni5Fe2 (M2052) alloy were investigated in terms
of frequency-dependent complex dynamics, using an ultrasonic pulse method. The longitudinal and transverse
waves show maximum decrements of about 2 and 1.8 at around 1.8 and 0.8 MHz, respectively, derived
from a single relaxation process. Frequency dispersion leads to increase in dynamic modulus and
delay in phase, suggesting growth (microkinking) of microtwin phases analogous to the stretching by micro-
Brownian rotation in rubbers.