Electric Tuning of Magnetization Dynamics and Negative Magnetic Permeability in Nanoscale Composite Multiferroics

Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with qualitatively new functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. Here we present a magnon-driven, strong interfacial ME effect acting within the spin-diffusion length of the order of nanometers. This type of linear ME interaction allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The ferromagnetic resonance unravels further an electric-field-induced negative magnetic permeability effect, pointing so to a new class of optical negative-index metamaterials based on composite multiferroics.