Multiferroics are defined as materials that exhibit more than one of the primary
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. ...
properties in the same phase:
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ferromagnetism
Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials a ...
– a magnetisation that is switchable by an applied magnetic field
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ferroelectricity
Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the a ...
– an electric polarisation that is switchable by an applied electric field
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ferroelasticity Ferroelasticity is a phenomenon in which a material may exhibit a spontaneous strain. Usually, a crystal has two or more stable orientational states in the absence of mechanical stress or electric field, i.e. remanent states, and can be reproducibly ...
– 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 In its most general form, the magnetoelectric effect (ME) denotes any coupling between the magnetic and the electric properties of a material. The first example of such an effect was described by Wilhelm Röntgen in 1888, who found that a dielectric ...
multiferroics'' that are simultaneously ferromagnetic and ferroelectric.
Sometimes the definition is expanded to include nonprimary order parameters, such as
antiferromagnetism
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions ...
or
ferrimagnetism
A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude so a spontaneous magnetization remains. This can for example occur when ...
. In addition, other types of primary order, such as ferroic arrangements of magnetoelectric multipoles of which