Switching ferroelectric twin boundaries

Switching ferroelectric twin boundaries
E.K.H. Salje
University of Cambridge, Department of Earth Sciences, Downing Street,
Cambridge UK
*e-mail: ekhard@esc.cam.ac.uk
The development of Domain Boundary Engineering has so far produced (super-)conducting, ferroelectric
and magnetic twin boundaries [1]. The first example of a polar domain boundary in a para-electric matrix
was CaTiO3 where polarity was first predicted by MD simulations [2] and subsequently observed by high
resolution transmission electron microscopy [3] and SHG observation [4]. Similar polar domain boundaries
were found in SrTiO3 [5]. In this case, the ferroelectric switching is not related to the switching of the entire
twin wall but is limited to Bloch lines of polarization P where the polarization is oriented perpendicular to
the wall [6]. Novel devices can be based on the functionalities of domain walls – such as twin boundaries –
and a key issue becomes the design and production of materials with very high domain boundary densities.
Various approaches will be discussed with emphasis on cold shearing rather than thermal quench. Size
effects are crucial for such materials. Nano-pillars and nano-wires contain twin-like interfaces when the
diameters are below a characteristic length (such as 2 -10 nm) while no such features seem to exist in larger
samples. The novel route to functionality is hence to use functional domain boundaries (which can be
chemically modified is novel ways by ‘chemical reactions in confined spaces’) rather than by changing bulk
properties. A progress report will be given.
1. Multiferroic Domain Boundaries as Active Memory Devices: Trajectories Towards Domain Boundary
Engineering, Salje E.K.H., ChermPhysChem, 11, 940 (2010).
2. Ferroelectric twin walls in CaTiO3, Goncalves-Ferreira L, Redfern S, Artacho E, Salje EKH, Phys. Rev.
Lett. 101, 097602 (2008).
3. Direct Observation of Ferrielectricity at Ferroelastic Domain Boundaries in CaTiO3 by Electron
Microscopy, Van Aert, Sandra; Turner, Stuart; Delville, Remi; et al., ADVANCED MATERIALS 24, 523
(2012)
4. Direct evidence of polar nature of ferroelastic twin boundaries in CaTiO3 obtained by second harmonic
generation microscope, Phys. Rev. B 89, 144109 (2014).
5. Domains within domains and walls within walls: evidence for polar domains in cryogenic SrTiO3, Salje,
E. K. H.; Aktas, O.; Carpenter, M. A.; et al. Phys. Rev. Lett. 111,247603 (2013).
6. Highly mobile vortex structures inside twin boundaries in SrTiO3, Zykova-Timan T, Salje
E.K.H.Appl.Phys. Lett. 104, 082907 (2014).
Curriculum Vitae Ekhard Salje is professor at the university of Cambridge, UK. He is fellow of the Royal Society and 3 other national academies. He has published over 500 papers and several books in the fields of ferroic phase transitions, elastic response theories and mineralogy. He works experimentally in spectroscopy (Raman and Infrared spectroscopy, resonance ultrasonic and piezoelectric ultrasonic spectroscopy RPS), computer simulation and analytical theories of coupled order parameters. His current work focuses on functional domain boundaries such as ferrielectric twin boundaries in CaTiO3.