Flexible high-sensitivity magnetoelectric thin film composites of solution-derived BiFeO3–PbTiO3 layers on Ni foils

Abstract

This study propels the development of high-sensitivity magnetoelectric (ME) thin-film composites for miniaturized energy harvesters, targeting applications like wearable self-powered sensors and actuators. ME structures are fabricated using a low-temperature solution deposition method, which is both cost-effective and straightforward for real device fabrication. The materials consist of BiFeO₃–PbTiO₃ ferro-piezoelectric perovskite thin films deposited on magnetostrictive nickel (Ni) substrates. For the first time, the study investigates films with sub-micron thickness (≤500 nm) of this high Curie temperature perovskite compound, and compares the performance of rigid and flexible structures. A major challenge was to attain good elastic coupling between the piezoelectric and magnetostrictive components to enhance magnetoelectric responses. A synergistic approach was used to achieve this goal combining low-temperature processing to minimize Ni oxidation and the introduction of a lanthanum manganite (La_0.7Sr_0.3MnO₃, LSMO) layer between the ferroelectric oxide and magnetic metal. The solution-derived LSMO acts simultaneously as a diffusion barrier, bottom electrode and crystallization promoter for the BF–PT film. Flexible structures demonstrate superior functional performance, with high remnant polarizations (P_R ∼ 50 μC cm⁻²) and voltage magnetoelectric coefficients (α_ME ∼ 100 mV cm⁻¹ Oe⁻¹), as well as appropriate voltage sensitivity to magnetic field (∼3.8 μV Oe⁻¹), demonstrating their suitability for multifunctional energy harvesting and sensing technologies.