New First-Order Phase Transition in High-Purity Ytterbium Metal

A first-order magnetic phase transition has been observed in high-purity Yb metal. It is characterized by a paramagnetic-to-diamagnetic transition with a large degree of hysteresis between 100 and 360 ^∘{}K, and appears to be associated with an fcc-hcp martensitic transformation. The occurrence of this transition is characteristic of high-purity metal and has not been previously reported. Several other properties such as the specific heat at 0 and 106 kOe, the volume and resistance changes the low-temperature resistivity, x-ray data, and the pressure and strain dependence of the transition are discussed. The diamagnetic phase is not superconducting above 0.015 ^∘{}K. The fcc phase was obtained from the hcp phase by applying strain at room temperature and was also investigated. It shows a strongly temperature-dependent paramagnetic susceptibility down to 1.4 ^∘{}K, but no magnetic ordering could be detected down to 1.0 ^∘{}K.