ANOMALOUS ELASTIC AND INELASTIC PROPERTIES OF ERBIUM IN C-AXIS HEXAGONAL DIRECTION

The Young's modulus E and internal friction Q-1 as functions of temperature in the region 4.2-380 K have been studied in detail for a sample of erbium single crystal oriented in the c-axis direction. Unique technique of flexural auto vibrations of a thin sample-bar on sound frequencies (approximately 1 kHz) was used for these investigations. Anomalous behavior of E(T) and Q-1 (T) curves was found, not only in the well known conventional magnetic transition points theta1 almost-equal-to 19 K, theta(B) almost-equal-to 53 K and theta2 almost-equal-to 84 K, but also in points of successive transitions between commensurate structures in the temperature region 27-42 K. At least five such transition points were unambiguously stated. Magnetic part of the Young's modulus E(m) has been theoretically computed from paramagnetic region data. Various possible mechanisms of internal friction in erbium are also discussed.