Low Temperature Phase Transitions of Gadolinium and Ytterbium Using Resonant Ultrasound Spectroscopy
AuthorKaplan Sakallioglu, Gunes
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Low temperature phase transitions in the lanthanides gadolinium (Gd) and ytterbium (Yb) were studied using the nondestructive technique of resonant ultrasound spectroscopy (RUS) coupled with a cryogenic system. Previous studies of these materials utilized a pulse-echo method that is not as robust as RUS. The advantagesof RUS include the ability to study very small samples and the ability to obtain all elastic properties of the sample from a single frequency spectrum. A laboratory system was developed combining RUS with a cryogenic cooling system capable of exploring the temperature range 13 K 340 K. The complex 4-f electronic structure of elemental Gd and Yb leads to continuous magnetic and first-order structural phase transitions within this temperature range. The results of measurements on Gd are consistent with those previously reported in literature, supporting the validity of RUS measurements on small lanthanide samples at low temperature. Three new phenomena are observed in the Yb measurements: a positive slope in resonance frequency versus temperature, hysteresis around a previously reported transition temperature of 315 K that decreases with temperature cycling, and hysteresis at low temperatures with discrete memory characteristics.