  Magnetoelectric coupling between magnetic and electric dipoles is one of the
cornerstones of modern physics towards developing the most energy-efficient
magnetic data storage. Conventionally, magnetoelectric coupling is achieved in
single-phase multiferroics or in magnetoelectric composite nanostructures
consisting of ferromagnetic and ferroelectric/piezoelectric materials. Here, we
demonstrate an electric-field-induced strain-mediated magnetoelectric effect in
ultrathin CoFeB/MgO magnetic tunnel junction employing non-piezoelectric
material, which is a vitally important structure for spintronic devices, by
using dynamical magnetoelectric and piezoresponse force microscopy measurement
techniques. We show that the applied electric-field induces strain in a few
atomic layers of dielectric MgO which is transferred to magnetostrictive CoFeB
layer, resulting in a magnetoelectric effect of magnitude up to 80.8 V cm-1
Oe-1 under -0.5 V. The demonstrated strain-mediated magnetoelectric effect with
an electric field in magnetic tunnel junctions is a significant step towards
exploring magnetoelectrically controlled spintronic devices for low-power and
high density magnetic data storage applications.
