We have studied the magnetic properties of Na$_2$Co$_2$TeO$_6$, which features a honeycomb lattice Co$^{2+}$ ions, through macroscopic characterization and neutron diffraction on powder sample. shown that this material orders in zig-zag antiferromagnetic structure. In addition to allowing linear magnetoelectric coupling, arrangement displays very peculiar spatial correlations, larger planes than between planes, do not evolve with temperature. investigated behavior by Monte Carlo calculations...

The failure dynamics in $\mathrm{Si}{\mathrm{O}}_{2}$-based porous materials under compression, namely the synthetic glass Gelsil and three natural sandstones, has been studied for slowly increasing compressive uniaxial stress with rates between 0.2 2.8 kPa/s. measured collapsed is similar to Vycor, which another $\mathrm{Si}{\mathrm{O}}_{2}$ but a different mesostructure. Compression occurs by jerks of strain release major collapse at point. acoustic emission shrinking samples during are...

Direct observations of the ferroelectric domain boundaries in LiNbO 3 are performed using high‐resolution high‐angle annular dark field scanning transmission electron microscopy imaging, revealing a very narrow width wall between 180° domains. The walls demonstrate local side‐way meandering, which results inclinations even when overall orientation follows polarization. These meanders contain kinks with “head‐to‐head” and “tail‐to‐tail” dipolar configurations therefore locally charged....

Abstract Field induced domain wall displacements define ferroelectric/ferroelastic hysteresis loops, which are at the core of piezoelectric, magnetoelectric and memristive devices. These collective scale invariant jumps with avalanche characteristics. Here, we analyse spatial distribution avalanches in ferroelectrics different transformation patterns: Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO contains complex domains needles junction patterns, while BaTiO has parallel straight domains. Nevertheless,...

The dynamic properties of elastic domain walls in BaTiO${}_{3}$ were investigated using resonance ultrasonic spectroscopy (RUS). sequence phase transitions is characterized by minima the temperature dependence RUS frequencies and changes $Q$ factors (resonance damping). Damping related to friction mobile twin boundaries (90\ifmmode^\circ\else\textdegree\fi{} ferroelectric walls) distorted polar nanoregions (PNRs) cubic phase. largest tetragonal ceramic materials but very low single crystals....

Abstract The ability to generate efficient giga–terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary waves (and vice versa), remain limited the megahertz range. Here, using generated at tens of gigahertz...

Acoustic emission has been measured and statistical characteristics analyzed during the stress-induced collapse of porous berlinite, AlPO4, containing up to 50 vol% porosity. Stress occurs in a series individual events (avalanches), each avalanche leads jerk sample compression with corresponding acoustic (AE) signals. The distribution AE energies can be approximately described by power law over large stress interval. We observed several mechanisms whereby less minerals show superposition...

Abstract Polar tweed was discovered in mechanically stressed LaAlO 3 . Local patches of strained material (diameter ca. 5 μm) form interwoven patterns seen birefringence images, Piezo-Force Microscopy (PFM) and Resonant Piezoelectric Spectroscopy (RPS). PFM RPS observations prove unequivocally that electrical polarity exists inside the The local piezoelectric effect varies greatly within reaches magnitudes similar to quartz. were mapped by shift E g soft-mode frequency Raman spectroscopy.

The total energy of acoustic emission (AE) events in externally stressed materials diverges when approaching macroscopic failure. Numerical and conceptual models explain this accelerated seismic release (ASR) as the approach to a critical point that coincides with ultimate Here, we report ASR during soft uniaxial compression three silica-based (SiO_{2}) nanoporous materials. Instead singular point, distribution AE energies is stationary, variations activity rate are sufficient presence...

We report two methods for direct observations of avalanches in ferroelectric materials during the motion domain walls. In first method, we use optical imaging techniques to derive changes structures under an electric field. All occur through small jumps (jerks) that obey avalanche statistics. second analyze jerks by their displacement current. Both reveal a power law distribution with energy exponent 1.6, agreement previous acoustic emission measurements, and integrated mean field theory....

A new type of materials combining a high-temperature plastic phase and low-temperature ferroelectric phase, the crystals, are promising for application in refrigeration systems based on solid-state caloric effects.

Abstract Recent studies carried out with atomic force microscopy or high-resolution transmission electron reveal that ferroic domain walls can exhibit different physical properties than the bulk of domains, such as enhanced conductivity in insulators, polar non-polar materials. In this review we show optical techniques, spite diffraction limit, also provide key insights into structure and ferroelectric ferroelastic walls. We give an overview uses, specificities limits these emphasize they...

Subcoercive field non-linearities in 0.5(Ba0.7Ca0.3TiO3)-0.5(BaZr0.2Ti0.8O3) (BCTZ 50/50) thin film elaborated using pulsed laser deposition are studied permittivity and phase angle of the third harmonic measurements as a function AC measuring EAC temperature. The global transition temperature Tmax for which is maximum, decreases from 330 to 260 K when increases. Rayleigh analysis dependence relative shows regular decrease domain wall motion contributions increases up an even more pronounced...

Antiferroelectrics are valuable dielectric materials, offering promise for both high energy storage and solid-state caloric cooling applications. However, few antiferroelectrics known or available. Therefore, it is crucial to discover design materials showing antiferroelectric behaviour. In this study, we fabricated highly ordered lead scandium tantalate ceramics doped with calcium. From calorimetry polarization-electric field loops, demonstrate the effect of calcium on thermal properties...

Monodomain and periodically poled LiNbO3 crystals (congruent composition) show dielectric piezoelectric resonances between 100 K 900 K. Dielectric measurements in some samples 10-100 kHz. These vanish under thermal anneal monodomain while they remain stable with high domain wall densities. The low activation energy of 0.18 eV suggests their electronic (bi-polaronic) origin. Resonant spectroscopy, RPS, shows two features virgin samples: a relaxation peak at 420 rapid hardening when the sample...

Abstract The understanding of domain structures, specifically walls, currently attracts a significant attention in the field (multi)-ferroic materials. In this article, we analyze contrast formation full electron microscopy applied to domains and walls uniaxial ferroelectric lithium niobate, which presents large 3.8 eV band gap for conductive have been reported. We show that transition from Mirror Electron Microscopy (MEM – electrons reflected) Low Energy (LEEM backscattered) gives rise...

The motion of domain walls and phase fronts in ferroelectric ferroelastic materials displays discrete, impulsive jumps, i.e. jerks, as indicators avalanches on a broad range scales. Several experimental techniques used to characterise these show that they are power law distributed share some statistical similarities with the observed during compression porous materials. Simulations attribute their origin kinks needle domains pinned by junctions between evolution amplitude driving field....

Elastic and anelastic properties of poled depoled single crystals Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 with compositions close to the morphotropic boundary have been investigated over temperature range 5–700 K by resonant ultrasound spectroscopy (RUS) at frequencies 0.1–1.2 MHz. Steep elastic softening occurs in a interval least 250 as Vogel-Fulcher freezing cubic → tetragonal transition point, Tc, are approached from above. This is understood terms coupling between acoustic modes...

The domain structure of uniaxial ferroelectric lithium niobate single crystals is investigated using Raman spectroscopy mapping. influence doping with magnesium and poling at room temperature studied by analysing frequency shifts walls their variations dopant concentration annealing conditions. It shown that defects are stabilized changes in the defect structures Mg can be probed shift modes. We show signatures polar bulk differ.

Ferroic domain walls could play an important role in microelectronics, given their nanometric size and often distinct functional properties. Until now, devices device concepts were mostly based on mobile ferromagnetic ferroelectric materials. A less explored path is to make use of polar nonpolar ferroelastic Indeed, while the character has been demonstrated, polarization control elusive. Here, we report evidence for electrostatic signature domain-wall calcium titanate...

In thin samples, such as membranes, kinks inside ferroelastic domain walls interact through “dipolar” interactions following a 1/d 2 decay, where d is the distance between walls. Simultaneously, samples relax by bending. Bending not possible in thick or can be suppressed films deposited on rigid substrate. these cases, wall-wall decay , monopoles would do. free-standing we show wide crossover regime and “monopolar” interactions. The surfaces of all characteristic relaxation patterns near...

Enabling on-demand control of heat flow is key for the development next-generation electronic devices, solid-state pumps, and thermal logic. However, precise agile tuning relevant microscopic material parameters adjusting conductivities remains elusive. Here, we study several single crystals lanthanum aluminate (LaAlO$_{3}$) with different domain structures show that ferroelastic walls behave as boundaries act like efficient controllers to govern conductivity. At low temperature (3 K),...

The elastic response of BaTiO$_3$ single crystals during electric field cycling at room temperature has been studied using in-situ Resonant Ultrasound Spectroscopy (RUS), which allows monitoring both the and anelastic changes caused by ferroelectric polarization switching. We find that first switching a virgin crystal is dominated ferroelastic 90{\deg} In subsequent switching, reduced domain pinning predominance 180{\deg} domains, as confirmed polarized light microscopy. RUS under therefore...