The realization of an artificial magnetoelectric heterostructure (FeCo/AlN) micro-beam resonator for ultra-high sensitivity magnetic sensing applications*

It's becoming more and more crucial to develop high sensitivity magnetic sensors that are chip-based and cryogen-free. Recent advances in artificial multiferroics and magnetostrictive/piezoelectric materials have opened the door to novel micron-scale magnetic field tunable resonator devices [1]. Here we show how magnetostrictive FeCo can be grown in-situ on a piezoelectric AlN micro-beam with coupled heterostructural strain. The resulting magnetostrictive properties of FeCo produce a considerable resonance shift when placed in a magnetic field [2]. The piezoelectric AlN underlayer captures this signal at two regions of maximum planar strain in the first harmonic mode. Our results reveal FeCo beams with a considerable strain induced resonance shift in a DC magnetic field when driven with either a piezo-shaker, or a small AC field. Furthermore, we demonstrate how the use of a beam geometry, rather than a standard resonant cantilever, fundamentally achieves an increase sensitivity to magnetic fields. [1] E. Lage, \textit{et. Al.,} \textit{Nature Materials} \textbf{11} (2012) [2] M. Staruch, \textit{et. Al.,} \textit{Appl. Phys. Lett.} \textbf{107} (2015)