Electric field control of the magnetic order parameter of magnetic pillars embedded in a ferroelectric matrix

Using polarized beam small angle neutron scattering (SANS) we quantitatively measured the influence of an electric field on correlation of magnetism in a ferroelectric/ferrimagnetic nanocomposite. The nanocomposite consists of \textasciitilde 12 nm wide pillars of CoFe$_{2}$O$_{4}$ (dark regions, inset figure left), a room temperature ferrimagnet, embedded in a ferroelectric, BaTiO$_{3}$, matrix (light regions, inset figure right). We used a model-free method to extract the correlations of the magnetic structure from the SANS data (figure below). We found a 700 kV/cm electric field induced a change of magnetization of \textasciitilde 2{\%} (scattering geometry, inset figure left). We explain our results using a simple representation for free energy that attributes coupling between electric polarization and magnetic order parameters to strain.