Controlling the magnetoelectric coupling in Ni/BiFe0.95Mn0.05O3 with a dielectric spacer

In artificial multiferroic heterostructures combining ferromagnetic transition metal films and bismuth ferrite layers the electric field control of the magnetic state is generally achieved through interface exchange coupling. Here we report a reversible and non-volatile magnetoelectric (ME) effect in Ni/BiFe0.95Mn0.05O3 bilayers originating primarily from a strain-transfer mechanism. The non-volatility of the ME effect is explained by an asymmetric piezoelectric strain response of the ferroelectric BiFe0.95Mn0.05O3 film with respect to the applied electric field, yielding two different states at remanence. We further show that the piezoelectric properties and the ferroelectric domain structure of the BiFe0.95Mn0.05O3 film can be controlled by tuning the screening of the polarization charge at the interface through an interleaved dielectric SrTiO3 spacer. As the dielectric spacer thickness is decreased, the strain-mediated ME response evolves from the typical butterfly-like hysteresis loop towards a rectangular shape, thereby making such artificial multiferroics suitable for non-volatile memory applications.