A joint neutron scattering and micromagnetic simulation approach to understanding magnetoelectric coupling in a mesoscale multiferroic

Heterogeneous structures consisting of two materials of different ferroic order with a coherent interface provide a natural path to magnetoelectric coupling. Recently we have been studying nanopillars of magnetostrictive CoFe$_{\mathrm{2}}$O$_{\mathrm{4}}$ in a matrix of piezoelectric BaTiO$_{\mathrm{3}}$ as a system for strain-mediated electric field control of the magnetic order parameter. Using the newly developed polarization capabilities of GP-SANS at ORNL to perform polarized beam small angle neutron scattering, we have demonstrated an electric field dependence of the CoFe$_{\mathrm{2}}$O$_{\mathrm{4}}$ magnetization at different magnetic fields. In combination with the neutron data, micromagnetics simulations using the Object Oriented MicroMagnetic Framework (OOMMF) have been employed to probe the spatial dependence of the magnetization. These simulations have established that a shell with large uniaxial anisotropy is required to replicate magnetometry and SANS data, which gives an indication of the depth of strain propagation across the interface.