Structural phase transitions in Pr${}_{1-x}$La${}_x$AlO${}_3$: Heat capacity and x-ray scattering studies

Abstract

Structural phase transitions in Pr${}_{1-x}$La${}_x$AlO${}_3$ (0 $\le x\le$ 1) single crystals have been studied through heat capacity and high-resolution x-ray scattering measurements. For PrAlO${}_3$, the heat capacity shows a sharp first-order peak at the rhombohedral to orthorhombic transition, while a classical mean-field anomaly is observed at the orthorhombic to monoclinic transition at lower temperatures. The transition temperature and the heat capacity anomaly of the two transitions diminish with increasing $x$, and only a single rhombohedral to monoclinic transition is observed for $x=0.8$. Although this latter transition is required by group theory to be first order, no such evidence is found in the heat capacity and x-ray scattering measurements. Instead, the results are consistent with mean-field criticality, with a small distribution of transition temperature originating from weak disorder.

22 pages, 6 figures

References in corpus (1)

• Critical X-ray Scattering Studies of Jahn-Teller Phase Transitions in TbV${}_{1-x}$As${}_x$O${}_4$