  Ferroic materials (ferromagnetic, ferroelectric, ferroelastic) usually divide
into domains with different orientations of their order parameter. Coupling
different ferroic systems creates new functionalities, for instance the
electrical control of macroscopic magnetic properties including magnetization
and coercive field. Here we show that ferroelastic domains can be used to
control both magnetic order and magnetization direction at the nanoscale with a
voltage. We use element-specific x-ray imaging to map the magnetic domains as a
function of temperature and voltage in epitaxial FeRh on ferroelastic BaTiO3.
Exploiting the nanoscale phase-separation of FeRh, we locally interconvert
between ferromagnetism and antiferromagnetism with a small electric field just
above room temperature. Our results emphasize the importance of nanoscale
ferroic domain structure to achieve enhanced coupling in artificial
multiferroics.
