Probing $Ca_3Ti_2O_7$ crystal structure at the atomic level: Insights from $^{111m}Cd/^{111}Cd$ PAC spectroscopy and ab-initio studies

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

doi:10.1103/PhysRevB.109.224101

paper

Probing $C a_{3} T i_{2} O_{7}$ crystal structure at the atomic level: Insights from $^{111 m} C d /^{111} C d$ PAC spectroscopy and ab-initio studies

arXiv:2402.09945 · doi:10.1103/PhysRevB.109.224101

Abstract

Perturbed angular correlation spectroscopy combined with $ab - ini t i o$ 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 $C a_{3} T i_{2} O_{7}$ , a hybrid improper ferroelectric. This procedure 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 $A c aa$ symmetry in the $C a_{3} T i_{2} O_{7}$ 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 $C a_{3} T i_{2} O_{7}$ ferroelectric polarization decrease within the 500-800~K temperature range.

Probing Ca3​Ti2​O7​ crystal structure at the atomic level: Insights from 111mCd/111Cd PAC spectroscopy and ab-initio studies

Abstract

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Probing $C a_{3} T i_{2} O_{7}$ crystal structure at the atomic level: Insights from $^{111 m} C d /^{111} C d$ PAC spectroscopy and ab-initio studies