Synopsis: Multiferroic under strain

A new material with strong magnetism and spin-phonon coupling could show multiferroicity at technologically relevant temperatures.
Synopsis figure
Illustration: Sarma Kancharla

Multiferroics are materials that have at least two types of long-range order. These orders can be ferromagnetic, ferroelectric, ferroelastic, or ferrotoroidic. True multiferroics, however, have coexisting ferroelectric and ferromagnetic orders and are the most promising for applications as well as for fundamental interest. Because the desire is to control properties of a multiferroic by adjusting a variable, such as electric or magnetic fields, an ever-expanding bestiary of candidate compounds are under eager experimental and theoretical scrutiny.

Many multiferroics have a perovskite structure that features corner-sharing octahedra of O2- ions. Recently, researchers have come up with strategies for controlling ferroic properties in perovskites through application of strain deliberately created in the crystal growth process. Now, in a paper published in Physical Review Letters, Jun Hee Lee and Karin Rabe of Rutgers University, US, report on the results of a first-principles study of the effects of epitaxial strain on a cubic perovskite compound SrMnO3.

The calculations predict a strong spin-phonon coupling that, under strain through a mechanism previously identified in EuTiO3, should result in multiferroic behavior above 100K. In bulk, SrMnO3 is not multiferroic (it is antiferromagnetic and paraelectric). This compound has not previously been identified as multiferroic, and one can reasonably hope that experimentalists will be keen to test out the predictions of Lee and Rabe. – Daniel Ucko


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