Phase Transformation in Samarium Induced by High Pressure and Its Effect on the Antiferromagnetic Ordering

Samarium undergoes a pressure induced phase transformation to double-hexagonal close-packed (La-type) structure at pressures around 40 kbar and temperatures near 300^∘{}C. It is retained metastably at atmospheric pressure. The new phase has a N\'eel temperature of 27^∘{}K as compared to 14.8^∘{}K noted for normal form of Sm. Pressure induced phase transformations observed in Gd, Sm, Ce, and La suggest that the sequence of polymorphic transformations under pressure in trivalent rare earths is in the order hcp{→}Sm -type{→}dhcp{→}fcc.