Details

Autor(en) / Beteiligte

• Oh, Yoon Seok
• Luo, Xuan
• Huang, Fei-Ting
• Wang, Yazhong
• Cheong, Sang-Wook

Titel

Experimental demonstration of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca,Sr)3Ti2O7 crystals

Ist Teil von

• Nature materials, 2015-04, Vol.14 (4), p.407-413

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2015

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• On the basis of successful first-principles predictions of new functional ferroelectric materials, a number of new ferroelectrics have been experimentally discovered. Using trilinear coupling of two types of octahedron rotation, hybrid improper ferroelectricity has been theoretically predicted in ordered perovskites and the Ruddlesden–Popper compounds (Ca 3 Ti 2 O 7 , Ca 3 Mn 2 O 7 and (Ca/Sr/Ba) 3 (Sn/Zr/Ge) 2 O 7 ). However, the ferroelectricity of these compounds has never been experimentally confirmed and even their polar nature has been under debate. Here we provide the first experimental demonstration of room-temperature switchable polarization in bulk crystals of Ca 3 Ti 2 O 7 , as well as Sr-doped Ca 3 Ti 2 O 7 . Furthermore, (Ca, Sr) 3 Ti 2 O 7 is found to exhibit an intriguing ferroelectric domain structure resulting from orthorhombic twins and (switchable) planar polarization. The planar domain structure accompanies abundant charged domain walls with conducting head-to-head and insulating tail-to-tail configurations, which exhibit a conduction difference of two orders of magnitude. These discoveries provide new research opportunities, not only for new stable ferroelectrics of Ruddlesden–Popper compounds, but also for meandering conducting domain walls formed by planar polarization. Room-temperature switchable polarization and the presence of charged domain walls with insulating and conducting configurations are now experimentally demonstrated in bulk (Ca,Sr) 3 Ti 2 O 7 .