In this paper, ultrasonic properties like ultrasonic attenuation, sound velocities, acoustic coupling constants and thermal relaxation time have been studied in hexagonal structured metals Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and Thulium (Tm) along unique axis at room temperature. For the evaluations of ultrasonic properties, secondand thirdorder elastic con...
