Enhanced magnetoelectric coupling in stretch-induced shear mode magnetoelectric composites

Magnetoelectric (ME) laminates consisting of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT)-based single crystals have recently attracted significant interest owing to their excellent piezoelectric properties. Particularly, ME laminates with d₁₅-mode single crystals exhibit the strongest ME coupling, but the fabrication of ME laminates with 15 shear modes is challenging. Herein, we propose the generation of a stretch–shear mode (d₁₅-mode) by clamping the opposite ends of the top and bottom magnetostrictive layers in symmetric ME laminates. Two different shear-stress-induced ME laminates were fabricated using Metglas/Galfenol as magnetostrictive layer, and 15-PMN-PZT as a piezoelectric layer. The ME laminates were studied under two different conditions, unclamped and clamped. Under unclamped condition, Galfenol/15-PMN-PZT/Galfenol (Metglas/15-PMN-PZT/Metglas) laminate showed maximum α_ME value of 1.71 V/cm∙Oe (0.62 V/cm∙Oe), while under clamped condition, Galfenol/d₁₅-PMN-PZT/Galfenol (Metglas/15-PMN-PZT/Metglas) laminate exhibited an enhanced α_ME value of 2.40 V/cm∙Oe (0.87 V/cm∙Oe), indicating successful generation of the stretch–shear mode. Under clamped condition, α_ME was enhanced by 140% compared with the that of the unclamped case, suggesting a 40% (0.25 V/cm∙Oe) contribution from the pure shear ME voltage coefficient along with the longitudinal extension contribution.