  We present a model artificial multiferroic system consisting of a
(011)-oriented ferroelectric Pb(Mg,Nb,Ti)O$_3$ substrate intimately coupled to
a ferromagnetic (La,Sr)MnO$_3$ film through epitaxial strain and converse
piezoelectric effects. Electric field pulse sequences of less than 6 kV/cm were
shown to induce large reversible and bistable remanent strains in the manganite
film. Magnetic hysteresis loops demonstrate that the changes in strain states
result in significant changes in magnetic anisotropy from a highly anisotropic
two-fold magnetic symmetry to a more isotropic one. Such changes in magnetic
anisotropy are reversible upon multiple cycles and are stable at zero applied
electric field, and are accompanied by large changes in resistivity. We
directly image the change between the two-fold and isotropic magnetic
configurations at the scale of a single ferromagnetic domain using X-ray
photoemission electron microscopy as a function of applied electric field
pulses. Imaging the domain reversal process as a function of electric field
shows that the energy barrier for magnetization reversal is drastically
lowered, by up to 70% as determined from free energy calculations, through the
anisotropic strain change generated by the ferroelectric substrate. Thus, an
electric field pulse can be used to 'set' and 'reset' the magnetic anisotropy
orientation and resistive state in the film, as well as lowering the coercive
field required to reverse magnetization, showing a promising route towards
electric-field manipulation of multifunctional nanostructures at room
temperature.
