During the initial phase of the project, we focused on developing various magnetoelectric materials, primarily through sputtering. These include CoxMn1-xN and CoxFe1-xN compounds, where external voltage can trigger motion of N ions; FeRh, where voltage induces ferromagnetic–antiferromagnetic metamagnetic transitions; complex oxide materials where O ions migrate under voltage; several heterostructures interfaced with ferroelectric substrates (PMN-PT, PMN-PZT) where voltage-driven strain mediates changes in diverse magnetic properties; and magnetostrictive films and structures adjacent ferroelectric films to study multiferroic effects. Some of these materials have been patterned via optical lithography and e-beam lithography, allowing us to explore magnetoelectric phenomena in sub-micrometer-sized dots.
All samples have been structurally and compositionally characterized using a broad range of experimental techniques, including scanning/transmission electron microscopy, XMCD/PEEM, and scanning probe microscopy (MFM and PFM modes). Magnetoelectric measurements were conducted in situ using both liquid and solid electrolytes, with custom-made electrolytic cells adapted for MOKE and VSM devices.
A key focus has been the voltage-driven motion of O²⁻ and N³⁻ ions. We demonstrated that their diffusion can induce analog changes in magnetic properties, including ON-OFF switching of ferromagnetism, a crucial effect for data security applications. In some cases, this process mimics synaptic activity (potentiation/depression effects), presenting opportunities for neuromorphic computing. Particularly intriguing is the possibility of wireless magneto-ionics via bipolar electrochemistry. We have also made progress in light-controlled ferromagnetism.
