Enhancing magnetoelectric coupling in Ni/PMN-PZT/Ni laminates by Ni electroplating

Adhesive-free 2-2 structured Ni/Pb(Mg_1/3Nb_2/3)O₃–PbZrTiO₃/Ni laminates were realized by directly electroplating magnetostrictive Ni onto [011]-oriented Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃ (PMN-PZT) single crystals for operation in the d₃₂ mode, thereby maximizing interfacial bonding and suppressing viscoelastic coupling losses associated with polymer adhesive layers. Finite element analysis comparing the presence/absence of an interlayer, single crystal vs ceramic piezoelectrics, and variations in Ni thickness shows that removing a polymeric adhesive layer increases the induced piezoelectric potential by approximately 13% that single crystals deliver ∼1.3 times higher output than ceramics at identical Ni thickness, and that the response grows, then saturates with Ni thickness under the same excitation condition. Uniform polycrystalline Ni layers with soft magnetic characteristics and controlled thickness were obtained by direct Ni electroplating on PMN-PZT single crystals. Under off-resonance condition, the direct magnetoelectric voltage coefficient increases with Ni thickness and reaches 6.9 V/cm Oe at bias fields below 100 Oe. At the electromechanical resonance, the coefficient is strongly amplified to 1419 V/cm Oe. These results indicate that combining direct Ni electroplating on 32 mode single crystals enhances interfacial stress transfer and magnetoelectromechanical conversion, providing a scalable route to high magnetoelectric responses for sensitive magnetic field sensing, low-frequency magnetoelectric antennas, and other applications.