Measuring the Dzyaloshinskii–Moriya interaction in a weak ferromagnet

Oxygen-mediated superexchange (or Dzyaloshinskii–Moriya) interactions result in weak ferromagnetism in oxides. A method based on the interference of synchrotron X-ray radiation is now shown to enable the determination of the sign of the Dzyaloshinskii–Moriya interaction in the prototypical weak ferromagnet iron borate. Magnetism—the spontaneous alignment of atomic moments in a material—is driven by quantum mechanical exchange interactions that operate over interatomic distances. Some magnetic interactions cause 1 , 2 , or are caused by 3 , 4 , a twisting of arrangements of atoms. This can lead to the magnetoelectric effect, predicted to play a prominent role in future technology, and to the phenomenon of weak ferromagnetism, governed by the so-called Dzyaloshinskii–Moriya interaction 5 , 6 , 7 , 8 . Here we determine the sign of the latter interaction in iron borate (FeBO 3 ) by using synchrotron radiation. We present a novel experimental technique based on the interference between two X-ray scattering processes, where one acts as a reference wave. Our experimental results are validated by state-of-the-art ab initio calculations. Together, our experimental and theoretical approaches are expected to open up new possibilities for exploring, modelling and exploiting novel magnetic and magnetoelectric materials.