Dresden 2017 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 15: Ferroics - Domains, Domain Walls and Skyrmions III

DF 15.6: Talk

Wednesday, March 22, 2017, 16:45–17:00, WIL B321

Local structure and structural coherence across the ferroelectric phase transition of h-YMnO₃ — •Sandra Helen Skjaervø¹, Quintin Meier², Emil Božin³, Simon Billinge^3,4, Mikhail Feygenson⁵, Nicola Spaldin², and Sverre Selbach¹ — ¹Dept. Mat. Sci. Eng, NTNU, Norway — ²Dept. Mat., ETH Zürich, Switzerland — ³Brookhaven Natl. Lab., Condensed Matter Phys. & Mat. Sci. Dept., Upton, USA — ⁴Columbia Univ, Dept. Appl. Phys. & Appl. Math., New York, USA — ⁵Forschungszentrum Jülich, JCNS

We use pair distribution function (PDF) analysis to investigate the nature of the high-temperature (∼1270 K) structural phase transition in multiferroic hexagonal YMnO₃. Upon the phase transition, the unit cell is known to triple as the Mn-O₅ polyhedra tilt in trimers and the Y atoms alternatively displace along the tilt axis, with a ferroelectric polarization arising from a coupling to a secondary Y displacement. Whether the polarization emerges simultaneously with the high-temperature structural distortion or a many hundred degrees lower remains controversial [1,2]. We have measured high-temperature neutron total scattering data at Oak Ridge Natl. Lab. We analyse the data as PDFs to investigate the short range order and structural coherence. We see that the transition shows both displacive and order-disorder character, and we explain the short range mechanisms behind the ferroelectric transition. [1] Lilienblum, M. et al. "Ferroelectricity in the multiferroic hexagonal manganites". Nature Physics, 11, 2015. [2] Nénert, G. et al., "Experimental evidence for an intermediate phase in the multiferroic YMnO₃". J. Phys.: Condensed Matter 19, no. 46, 2007.