Low-field giant magneto-ionic response in polymer-based nanocomposites.

The future of magnetoelectric (ME) materials is closely linked to the optimization of the ME response on nanocomposites or to the introduction of new effects to achieve higher ME performance from low magnetic fields. Here, we report a P(VDF-TrFE)/[C4mim][FeCl4] nanocomposite with a magneto-ionic response that produces giant magnetoelectric coefficients up to ≈10 V cm-1 Oe-1. This response comprises a magnetically triggered ionic/charge movement within the porous structure of the polymer, being this a novel phenomenon never experimentally observed or explored in magnetoelectric composites. This work successfully demonstrates the concept of exploring magnetic ionic liquids, such as [C4mim][FeCl4], in polymer-based magnetoelectric nanocomposites, suitable for low-field magnetic sensing devices. Such nanocomposites have remarkable potential for applications, not only because they exhibit a high ME response with scalable production and with good reproducibility but also because this coupling between magnetic order and electric order via ionic effects can lead to additional novel effects.