Magnetic-Field Induced Charge Accumulation in Scalable Magnetoelectric PVDF-TrFE/Ni Composite Devices

Abstract

This study investigates the direct magnetoelectric effect in thin film composites comprising a 550 nm thick poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) layer spin-coated onto a 500 µm thick Ni foil substrate. Direct measurements of charge accumulation on dot capacitors with Au top electrodes, induced by the rotation of Ni magnetization from in-plane to out-of-plane orientation by an applied magnetic field, reveal pronounced magnetoelectric coupling. Polarization differences between in-plane and out-of-plane magnetization states of up to (13.8 ± 0.8) × 10⁻⁴ µC cm⁻² are derived from charge measurements. This corresponds to a maximum open circuit voltage difference of up to 75 ± 6 mV and a magnetoelectric coupling coefficient with respect to magnetization changes of 310 ± 27 mVA⁻¹. Finite element simulations using COMSOL Multiphysics corroborate experimental findings, indicating near-independence of generated polarizations and open circuit voltages when lateral capacitor dimensions are reduced into the nanometer range. Simulations of nanoscale pillar devices on rigid substrates, employing materials with optimized piezoelectric and magnetostrictive parameters, predict the potential for generating large open circuit voltage differences exceeding 2 V, highlighting the prospects of such devices for spintronic applications.