Direct observation of polar tweed in LaAlO3

Abstract

Polar tweed was discovered in mechanically stressed LaAlO3. Local patches of strained material (diameter ca. 5 μm) form interwoven patterns seen in birefringence images, Piezo-Force Microscopy (PFM) and Resonant Piezoelectric Spectroscopy (RPS). PFM and RPS observations prove unequivocally that electrical polarity exists inside the tweed patterns of LaAlO3. The local piezoelectric effect varies greatly within the tweed patterns and reaches magnitudes similar to quartz. The patterns were mapped by the shift of the Eg soft-mode frequency by Raman spectroscopy.

Ferroelastic Domain Boundary-Based Multiferroicity

“…More generally, it was then shown that all complex ferroelastic patterns show polarity, including tweed patterns [98]. Experimentally, Salje et al [42] reported the first direct evidence for piezoelectricity of a tweed structure in LaAlO 3 , where the uniform parent structure is centrosymmetric and shows no polarity [99].…”

“…It was then argued that tweed structures are polar, either via the flexoelectric effect or via bilinear coupling between the strain and local dipole moments [36][37][38][39][40][41]. Recently, Salje et al [42] reported the first experimental evidence for piezoelectricity of a tweed structure in LaAlO 3 , where the uniform parent structure is centrosymmetric and shows no bulk polarity.…”

Superdomain dynamics in ferroelectric-ferroelastic films: Switching, jamming, and relaxation

“…[8][9][10] The idea of coarsening has not often previously been extended to wrinkles and domains, rather than grains, but except for very short times the dynamics may be similar in the two cases: [11,12] Put simply, a different kind of coarsening creates superdomain "bundles" which display both ferroelastic and ferroelectric properties [13]. In [11] X. Chen and [12] S. Chen et al describe the coarsening of wrinkles in viscoelastic layers and of jamming in magnetic domains; and in [14][15][16][17] Salje et al and Zvelindovsky et al describe coarsening in multidomain systems. They also show that shearing slows down coarsening of structures at later stages of phase separation, trapping the system in kinetically driven non-equilibrium metastable states.…”

“…He points out that complex domain structures, including tweed, may be stabilized by defects and that tweed structures are polar, either via the flexoelectric effect or via bilinear coupling between the strain and local dipole moments. Recently, Salje et al [16] reported the first experimental evidence for piezoelectricity of a tweed structure in LaAlO3, where the uniform parent structure is centrosymmetric and shows no bulk polarity.…”

“…Both Chen and Zvelindovsky et al found [12][13][14][15][16][17][18] power-law dependences with exponents very near ¼, as does Sinha [14]. There is a good earlier study of this problem by Kohn and Otto [19] based upon surface diffusion.…”