In situ X-ray diffraction investigation of electric-field-induced switching in a hybrid improper ferroelectric

Abstract

Improper ferroelectric mechanisms are increasingly under investigation for their potential to expand the current catalogue of functional materials whilst promoting couplings between ferroelectricity and other technologically desirable properties such as ferromagnetism. This work presents the results of an in situ synchrotron X-ray diffraction experiment performed on samples of Ca2.15Sr0.85Ti2O7 in an effort to elucidate the mechanism of hybrid improper ferroelectric switching in this compound. By simultaneously applying an electric field and recording diffraction patterns, shifts in the intensity of superstructure peaks consistent with one of the switching mechanisms proposed by Nowadnick & Fennie [Phys. Rev. B, (2016), 94, 104105] are observed. While the experiment only achieves a partial response, comparison with simulated data demonstrates a preference for a one-step switching mechanism involving an unwinding of the octahedral rotation mode in the initial stages of switching. These results represent some of the first reported experimental diffraction-based evidence for a switching mechanism in an improper ferroelectric.

Pressure-Dependent Phase Transitions in Hybrid Improper Ferroelectric Ruddlesden-Popper Oxides

“…We have recently attempted to probe the behaviour of the distortion modes observed in Ca 2.15 Sr 0.85 Ti 2 O 7 under the effect of an applied electric field, finding an subtle preference for the X + 2 rotation mode to unwind rather than the X − 3 tilt mode. 24 These results, coupled with the results of the temperature-based investigations, strongly imply that the X + 2 mode is the softer of the two for this phase.…”

Out-of-plane ferroelectricity and robust magnetoelectricity in quasi-two-dimensional materials

“…There are other possible experiments to further elucidate the FE and ME behaviors in our proposed materials. For example, in situ synchrotron x-ray diffraction experiment under applied electric fields can help understand the FE switching mechanism, as already demonstrated in HIF oxide Ca 2.15 Sr 0.85 Ti 2 O 7 (59). Variable-temperature high-resolution neutron diffraction is also helpful in observing the coupling effect between electric polarization and magnetic order (60).…”

Constrained non-negative matrix factorization enabling real-time insights of $\textit{in situ}$ and high-throughput experiments

“…Xray diffraction (XRD) and pair distribution function (PDF) analysis are necessary for comprehending energy materials across batteries, 13,14 catalysis, 15,16 photovoltaics, 17 and multiferroics. 18 This challenge is most pressing at central facilities, which have the technological capacity to produce vast amounts of data across variable sample environments.…”