Piezomagnetism is a phenomenon observed in some antiferromagnetic crystals. It is characterised by a linear coupling between the system's magnetic polarisation and mechanical strain. In a piezomagnetic, one may induce a spontaneous magnetic moment by applying physical stress, or a physical deformation by applying a magnetic field.
Piezomagnetism differs from the related property of magnetostriction; if an applied magnetic field is reversed in direction, the strain produced changes signs. 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. 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 time reversal forbids the property.
The first experimental observation of piezomagnetism was made in 1960, in the fluorides of cobalt and manganese.