ELASTIC MODULI AND ULTRASONIC ATTENUATION OF GADOLINIUM TERBIUM DYSPROSIUM HOLMIUM AND ERBIUM FROM 4.2 TO 300 DEGREES K

The longitudinal and transverse acoustic velocities and the ultrasonic attenuations in high-purity polycrystalline gadolinium, terbium, dysprosium, holmium, and erbium metals have been measured by a pulse technique at a frequency of 10 MHz between 4.2 and 300°K. The variations with temperature of the Young moduli E, shear moduli G, adiabatic compressibilities Ks, and Debye temperatures D have been determined. The anomalies observed in the elastic and anelastic behavior were correlated with the magnetic transitions known to occur in these metals. The behavior of the elastic properties and ultrasonic attenuations in the vicinity of the majority of the magnetic transition points was in accord with the criteria of Landau et al.'s theories of second-order phase changes. Exceptions are the ferromagnetic transitions in terbium and dysprosium, and the change in the antiferromagnetic structure of erbium at 56°K. The character of the elasticity anomalies in these three cases tends to indicate that they are of first order. The abrupt change in the easy direction of magnetization in gadolinium at 224°K is sharply manifested in the elastic and anelastic properties. Determination of these properties in holmium revealed an anomalous behavior at 70°K. The temperature variation of the Debye temperatures in gadolinium, terbium, dysprosium, holmium, and erbium depicts the elasticity behavior. The limiting Debye temperatures at 0°K are, in general, higher than those obtained from specific-heat measurements. © 1968 The American Physical Society.