Probing Ca 3 Ti 2 O 7 crystal structure at the atomic level: Insights from perturbed angular correlation spectroscopy and ab initio studies

Author(s):Show less -

Rocha-Rodrigues, P. ; Miranda, I. P. ; Santos, S. S. M. ; Oliveira, G. N. P. ; Leal, T. ; Marcondes, M. L. ; Correia, J. G. ; Assali, L. V. C. ; Petrilli, H. M. ; Lopes, A. M. L. ; Araujo, J. P.

• Document type: Journal article
• Source: PHYSICAL REVIEW B; v. 109, n. 22, p. 12-pg., 2024-06-03.

Abstract

Perturbed angular correlation spectroscopy combined with ab initio electronic structure calculations is used to unravel the structural phase transition path from the low -temperature polar structure to the high -temperature structural phase in Ca 3 Ti 2 O 7 , a hybrid improper ferroelectric. The experimental procedure, conducted at ISOLDE, explores the unique features of a local probe environment approach by monitoring the evolution of the electric field gradient tensor at the calcium sites. The local environments, observed above 1057 K, confirm a structural phase transition from the A 2 1 am symmetry to an orthorhombic Acaa symmetry in the Ca 3 Ti 2 O 7 crystal lattice, disagreeing with the frequently reported avalanche structural transition from the polar A 2 1 am phase to the aristotype I 4 / mmm phase. Moreover, the EFG temperature dependency, within the A 2 1 am temperature stability, is shown to be sensitive to the recently proposed Ca 3 Ti 2 O 7 ferroelectric polarization decrease within the 500-800 K temperature range. (AU)

• FAPESP's process: 22/10095-8 - New materials for energy and spintronics
• Grantee: Helena Maria Petrilli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/07760-4 - Functional lattice instabilities in naturally layered perovskites
• Grantee: Helena Maria Petrilli
• Support Opportunities: Regular Research Grants