Magneto-orbital helices: An emergent electronic texture in multiferroics

11 December 2012

Materials in which magnetism can be controlled with an electric voltage are one of the most promising routes towards a new generation of high-density, non-volatile computer memories. In an article published today in Nature Communications, Natasha Perks and co-workers from Oxford Physics, ILL (France), and CNRS (France) report how such control can be achieved with the help of a unique magneto-orbital texture, observed for the first time in single crystals of CaMn7O12. The electronic occupation on distinct manganese orbitals varies periodically throughout the crystal, coupling to the magnetic moments (spins) of the same manganese atoms to give rise to an unprecedented “magneto-orbital helix” (see figure). This new electronic state is not only elegant, but also capable of leading to important technological developments, because CaMn7O12 has the largest magnetically induced ferroelectric polarization (multiferroicity) measured to date – as previously discovered also at the Clarendon Laboratory. The operating temperature of CaMn7O12, 90 K, is still too low for technological applications. However, the Clarendon group (and, no doubts, its competitors…) are busy developing new materials where magneto-orbital helices (or analogous structures) can “do their magic” at room temperature – a step that would lead to the development of key components in future technology.

Reference: N. Perks et al., Nature Communications 3 , 1277 (2012)