Unravelling the magnetodielectric characteristics of strain-coupled PMN-PT/FSMA multiferroic heterojunction toward flexible MEMS applications

Abstract

Flexible microelectromechanical (MEMS) devices are poised to scaffold technological innovations in the fields of wearable sensors, implantable health monitoring systems and touchless human-machine interaction. Here, we report the magnetoelectric properties of cost-effective and room-temperature sensitive 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3/Ni50Mn35In15 (PMN-PT/ferromagnetic shape memory alloy (FSMA)) multiferroic heterostructure integrated on flexible stainless steel substrate via RF/DC magnetron sputtering technique. The growth of the pure perovskite phase of PMN-PT without any pyrochlore impurity is confirmed by the dominant (002) orientation of the tetragonal PMN-PT. The double logarithmic plot of current density with electric field validates the Ohmic conduction mechanism with low leakage current density of ∼10−6 A cm−2. The anomaly observed in temperature-dependent dielectric and ferroelectric characteristics of the heterostructure overlap with the martensite transformation regime of the bottom Ni–Mn–In (FSMA) layer. The PMN-PT/Ni–Mn–In multiferroic heterostructure exhibits a significant magnetodielectric effect of ∼3% at 500 Oe and can be used as an ultra-sensitive room-temperature magnetic field sensor. These results have been explained by an analytical model based on strain-mediated magnetoelectric coupling between interfacially coupled PMN-PT and Ni–Mn–In layers of the multiferroic heterostructure. Furthermore, the excellent retention of magnetodielectric response up to 200 bending cycles enhances its applicability towards flexible MEMS devices. Such PMN-PT based multiferroic heterostructures grown over the flexible substrate can be a potential candidate for piezo MEMS applications.