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Ferroic
Ferroics is the generic name given to the study of ferromagnets, ferroelectrics, and ferroelastics. Overview The basis of ferroics 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 T_c. 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 T_c 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. In ferroelectrics, upon lowering the temperature below T_c, a spontaneous dipole moment is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiferroics
Multiferroics are defined as materials that exhibit more than one of the primary ferroic properties in the same phase: * ferromagnetism – a magnetisation that is switchable by an applied magnetic field * ferroelectricity – an electric polarisation that is switchable by an applied electric field * ferroelasticity – a deformation that is switchable by an applied stress While ferroelectric ferroelastics and ferromagnetic ferroelastics are formally multiferroics, these days the term is usually used to describe the ''magnetoelectric multiferroics'' that are simultaneously ferromagnetic and ferroelectric. Sometimes the definition is expanded to include nonprimary order parameters, such as antiferromagnetism or ferrimagnetism. In addition, other types of primary order, such as ferroic arrangements of magnetoelectric multipoles of which ferrotoroidicity is an example, have also been recently proposed. Besides scientific interest in their physical properties, multiferroics have pote ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
