A flexible magnetoelectric field-effect transistor with magnetically responsive nanohybrid gate dielectric layer

Flexible magnetoelectric (ME) materials have been studied for new applications such as memory, energy harvesters, and magnetic field sensors. Herein, with the widely studied and progressive advantages of ME phenomena in the multiferroic field, we demonstrate a new approach for utilizing flexible ME materials as gate dielectric layers in ME organic field-effect transistors (ME-OFET) that can be used for sensing a magnetic field and extracting the ME properties of the gate dielectric itself. The magnetoelectric nanohybrid gate dielectric layer comprises sandwiched stacks of magnetostrictive CoFe₂O₄ nanoparticles and a highly piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) layer. While varying the magnetic field applied to the ME gate dielectric, the ME effect in the functional gate dielectric modulates the channel conductance of the ME-OFET owing to a change in the effective gate field. The clear separation of the ME responses in the gate dielectric layer of ME-OFET from those of the other parameters was demonstrated using the AC gate biasing method and enabled the extraction of the ME coefficient of ME materials. Additionally, the device shows high stability after cyclic bending of 10, 000 cycles at a banding radius of 1.2 cm. The device has significant potential for not only the extraction of the intrinsic characterization of ME materials but also the sensing of a magnetic field in integrated flexible electronic systems.