Piezomagnetism

Piezomagnetism is a phenomenon observed in some antiferromagnetic and ferrimagnetic crystals. It is characterized by a linear coupling between the system's magnetic polarization and mechanical strain. In a piezomagnetic material, one may induce a spontaneous magnetic moment by applying mechanical 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 fields, which is not true of magnetostriction.<ref>Cullity, B. D. (1971). "Fundamentals of Magnetostriction". Journal of Metals. 23 (1): 35–41. Bibcode:1971JOM....23a..35C. doi:10.1007/BF03355677.</ref> According to the Institute of Electrical and Electronics Engineers (IEEE):

"Piezomagnetism is the linear magneto-mechanical 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".

<ref>IEEE Standard on Magnetostrictive Materials: Piezomagnetic Nomenclature. doi:10.1109/IEEESTD.1991.101048. ISBN 0-7381-4558-0.</ref>

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.<ref>Dzialoshinskii, I. E. (1958). "The problem of piezomagnetism" (PDF). Soviet Phys. JETP. 6: 621.</ref>

The first experimental observation of piezomagnetism was made in 1960, in the fluorides of cobalt and manganese.<ref>Borovik-Romanov, A.S. (1960). "Piezomagnetism in the antiferromagnetic fluorides of cobalt and manganese" (PDF). Soviet Phys. JETP. 11: 786.</ref>

The strongest piezomagnet known is uranium dioxide, with magnetoelastic memory switching at magnetic fields near 180,000 Oe at temperatures below 30 kelvins.<ref>Jaime, M.; Saul, A.; Salamon, M.; Zapf, V. S.; Harrison, N.; Durakiewicz, T.; Lashley, J. C.; Andersson, D. A.; Stanek, C. R.; Smith, J. L.; Gofryk, K. (2017). "Piezomagnetism and magnetoelastic memory in uranium dioxide". Nature Communications. 8 (1): 99. Bibcode:2017NatCo...8...99J. doi:10.1038/s41467-017-00096-4. PMC 5524652. PMID 28740123.</ref>