Piezomagnetism
Encyclopedia
Piezomagnetism is a phenomenon observed in some antiferromagnetic crystals. It is characterised by a linear
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...

 coupling between the system's magnetic polarisation and mechanical strain
Strain (materials science)
In continuum mechanics, the infinitesimal strain theory, sometimes called small deformation theory, small displacement theory, or small displacement-gradient theory, deals with infinitesimal deformations of a continuum body...

. In a piezomagnetic, one may induce a spontaneous magnetic moment
Magnetic moment
The magnetic moment of a magnet is a quantity that determines the force that the magnet can exert on electric currents and the torque that a magnetic field will exert on it...

 by applying physical stress, or a physical deformation by applying a magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

.

Piezomagnetism differs from the related property of magnetostriction
Magnetostriction
Magnetostriction is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of material's magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ...

; if an applied magnetic field is reversed in direction, the strain produced changes sense. Additionally, a non-zero piezomagnetic moment can be produced by mechanical strain alone, at zero field - this is not true of magnetostriction. According to IEEE: "Piezomagnetism is the linear magnetomechanical effect analogous to the linear electromechanical effect of piezoelectricity
Piezoelectricity
Piezoelectricity is the charge which accumulates in certain solid materials in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure...

. Similarly, magnetostriction and electrostriction are analogous second-order effects. These higher-order effects can be represented as effectively first-order when variations in the system parameters are small compared with the initial values of the parameters".

The piezomagnetic effect is made possible by an absence of certain symmetry elements in a crystal structure; specifically, symmetry under inversion of either space or time forbid the property.

The first experimental observation of piezomagnetism was made in 1960, in the fluorides of cobalt and manganese.
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