Study of Magnetoelectric Coupling at the Ferroelectric Vinylidene Fluoride/Ferroelectric Cobalt Interface.*

The implementation of organic ferroelectric materials in devices could lead to significantly increased device functionality, as they effectively combine the numerous advantages of organic-based electronics with the useful bi-stable polarization characteristic of ferroelectricity. Magnetoelectric coupling, for example, between poly(vinylidene fluoride), or PVDF, and ferromagnetic cobalt thin films has been well established . However, open questions remain, concerning the role and structure of the Co/PVDF interface. The VDF_n oligomer (n=15), with high remanent polarization, better crystallinity, and vacuum deposition capability, has an edge over its polymer counterpart. We have shown that the Co/VDF interface is pristine , but only displays weak magnetoelectric coupling. Inserting a high-K dielectric MgO thin film between the ferroelectric VDF and ferromagnetic Co layers may help strengthen the coupling. We also expound on the effects that annealing has on the Co/MgO interface: it results in the migration of oxygen from Co to MgO, changing the magnetic anisotropy from out-of-plane to in-plane. We present data on the magnetoelectric coupling in these metal/organic heterostructures with and without the MgO interlayer