Abstract
La has a high-temperature form crystallizing in the primitive tetragonal Ca-type structure (space group ; Å, Å), and a low-temperature form of the body-centered tetragonal Th type (space group ; Å, Å). Both structures are Ba-type derivatives. The high-temperature modification may be quenched from above the transformation temperature of 1720°C and becomes superconducting at 1.6 K, while the low-temperature modification is normal down to 1 K. The structures of both modifications have been refined in single-crystal studies. The exceptional polymorphism of La is discussed, emphasizing structural relationships and the occurrence of superconductivity in the high-temperature modification.
- Received 28 December 1982
DOI:https://doi.org/10.1103/PhysRevB.28.1389
©1983 American Physical Society