Abstract
We have studied the polarized infrared reflectance of a stoichiometric single crystal of through the Abma () (low-temperature orthorhombic) →P/ncm () (low-temper- ature tetragonal) structural phase transition. This transition, which occurs near 70 K, involves a rigid tilt of the Ni- octahedra and produces distinct changes in the infrared-active phonons. Our observations are consistent with a first-order phase transition. This phase transition also occurs in , and has a profound influence on superconductivity in that material.
- Received 2 July 1990
DOI:https://doi.org/10.1103/PhysRevB.42.8787
©1990 American Physical Society