We plan to continue our previous investigation on the influence of thin Mg insert layers on magnetism at buried interfaces in structures that model the lower electrode/barrier interface in technologically-relevant crystallinemagnetic tunnel junctions (MTJs). Inserting a thin layer of Mg prior to depositing MgO enhances the performance of annealed MTJ devices: however the reason for this enhancement is not well understood. Specular and off-specular polarized neutron reflectivity on annealed and unannealed structures with different Mg insert thicknesses will allow us to gain a basic understanding into how Mg insert layers improve MTJ device performance. Structural and magnetic properties of the buried CoFe(B)/MgO interface will be extracted, complementing our existing electron microscopy and synchrotron studies: this allocation will allow us to complete the dataset obtained previously.