Anomalous Shear Ultrasonic Attenuation Peak at 95.5 K in Holmium.

摘要

A strong shear phonon interaction peak has been observed in two single crystals of holmium at 95.5 K. A very small velocity change is also observed at this temperature. The critical exponent for this peak appears to be 1. The magnetic field dependence of this peak has been investigated both as a function of strength and orientation. The attenuation peak is shifted towards higher temperatures by a magnetic field when it is parallel either to the c axis or the a axis while the sound wave propagates along the c axis. The attenuation coefficient exhibits two fold symmetry which goes as sin squared of theta. A rotation of the magnetic field around the b axis starting from the a axis and ending at the c axis produces two maxima in attenuation if the temperature is slightly above 95.5 K. A theoretical explanation for the source of this peak has not yet been developed. (Author)