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Layered Two-Phase Magnetoelectric Materials
Published in Sam Zhang, Dongliang Zhao, Advances in Magnetic Materials, 2017
Zhaofu Du, Sam Zhang, Dongliang Zhao, Tat Joo Teo, Rajdeep Singh Rawat
Traditionally, ferroic properties include ferroelectricity, ferromagnetism, and ferroelasticity. However, current practice tends to exclude ferroelasticity but encompasses ferrotoroidicity (i.e., an ordered arrangement of magnetic vortices) and even antiferroicity [1]. Multiferroic materials are materials that exhibit more than one primary ferroic property in a single material. Figure 6.1 illustrates ferroic properties of multiferroic materials.
Electro-optic Ceramics and Devices
Published in Lionel M. Levinson, Electronic Ceramics, 2020
Domain patterns, regions of uniform and homogeneous spontaneous electrical polarization within a grain or between several grains, can also be revealed in the microstructure of ferroelectric (memory and electro-optic) ceramics when chemical etching techniques are used. Examples of these patterns are shown in Fig. 23. The domains show up as a bilevel structure because one end of the electric dipole etches faster chemically than the opposite end. Distinctive features here are (1) the absence of etched grain boundaries, (2) domain structures bridging grain boundaries, indicating little disorder at the boundary, and (3) the size of the domains, approximately 5 μm. In reality, domains may vary widely in size, from 0.5 to 10 μm, in these materials. Furthermore, they are readily influenced by (1) grain size, (2) poling condition, and (3) stress. With respect to the effect of grain size, grains of 2 μm or less are usually single domain, whereas grains greater in diameter than 2 μm most often consist of more than one domain. The ultimate size of the domains for large grain size material cannot be predicted and depends heavily on the width of the grain boundary and the orientation mismatch between grains. Poling also has an influence on domain size because, as mentioned previously, the poling process is one of reorienting the spontaneous polarization of the crystallites, which if reasonably complete will produce a material with relatively few, but large, domains. Thus, a virgin memory ferroelectric will usually exhibit a vivid domain pattern, but a poled material will not. Finally, stress also has an effect on the domain pattern of these materials since they are ferroelastic as well as ferroelectric. Ferroelasticity is the phenomenon whereby a mechanical stress can shift the orientation states of spontaneous polarization, i.e., reorientation of strain-relieving domains (90° domains for the tetragonal phase and 71° and 109° domains for the rhombohedral phase). As far as the ferroelastic ceramic is concerned, this behavior can have nearly the same effect as poling; however, the difference is that poling can align domains into a pattern of like polarity but mechanical stress cannot.
A genetic approach to the dielectric investigation of the high-temperature phase transition of TEA2MnCl4 crystals
Published in Phase Transitions, 2019
Jacek Radojewski, Agnieszka Ciżman
Ferroelasticity can be successfully employed in micro-electro-mechanical-systems [2–4] such as sub-micro-positioning, micro-actuators, nano-displacement sensors and cantilevers. These devices can be applied in instrumentation of scanning probe or near-field microscopes, in sub-micro-manipulators for nano-technology, in medical equipment for micro-surgery or in bio-implanted systems (lead-free ferroics only). Ferroelastic materials are of a great interest today.