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| | Andrew Berryhill is what his spouse loves to contact him and he completely digs that title. Credit authorising is how he makes money. For many years he's been residing in Mississippi and he doesn't plan on changing it. To perform domino is some thing I truly enjoy doing.<br><br>Here is my webpage ... are psychics real ([http://cartoonkorea.com/ce002/1093612 cartoonkorea.com]) |
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| '''Ferroics''' is the generic name given to the study of [[ferromagnets]], [[ferroelectrics]], and [[ferroelastics]]. The basis of this study is to understand the large changes in physical characteristics that occur over a very narrow temperature range. The changes in physical characteristics occur when [[phase transitions]] take place around some critical temperature value, normally denoted by <math>T_c</math>. Above this critical temperature, the crystal is in a nonferroic state and does not exhibit the physical characteristic of interest. Upon cooling the material down below <math>T_c</math> it undergoes a spontaneous [[phase transition]]. Such a [[phase transition]] typically results in only a small deviation from the nonferroic crystal structure, but in altering the shape of the [[unit cell]] the [[point symmetry]] of the material is reduced. This breaking of symmetry is physically what allows the formation of the ferroic phase.
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| In ferroelectrics, upon lowering the temperature below <math>T_c</math>, a spontaneous [[Polarity|dipole moment]] is induced along an axis of the unit cell. Although individual dipole moments can sometimes be small, the effect of <math>10^{24}</math> unit cells gives rise to an electric field that over the bulk substance that is not insignificant. An important point about ferroelectrics is that they cannot exist in a '''centrosymmetric''' crystal. A '''centrosymmetric''' crystal is one where a lattice point <math>\left (x,y,z \right )</math> can be mapped onto a lattice point <math>\left ( -x,-y,-z \right )</math>.
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| Ferromagnets is a term that most people are familiar with, and, as with ferroelastics, the spontaneous magnetization of a ferromagnet can be attributed to a breaking of point symmetry in switching from the paramagnetic to the ferromagnetic phase. In this case, <math>T_c</math> is normally known as the Curie Temperature.
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| In ferroelastic crystals, in going from the nonferroic (or '''prototypic phase''') to the ferroic phase, a spontaneous strain is induced. An example of a ferroelastic [[phase transition]] is when the crystal structure spontaneously changes from a [[tetragonal]] structure (a square prism shape) to a [[monoclinic]] structure (a general [[parallelepiped]]). Here the shapes of the unit cell before and after the [[phase transition]] are different, and hence a [[Strain (materials science)|strain]] is induced within the bulk.
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| In recent years a new class of ferroic materials has been attracting increased interest. These [[multiferroics]] exhibit more than one ferroic property simultaneously in a single phase.
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| ==See also==
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| * [[Ferroelectric effect]]
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| * [[Ferromagnetism]]
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| * [[Piezoelectricity]]
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| * [[Pyroelectricity]]
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| * [[Ferroelasticity]]
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| * [[Multiferroics]]
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| [[Category:Condensed matter physics]]
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| [[Category:Magnetic ordering]]
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