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Mechanical flexible electronic/spintronic devices have shown enormous application potential to impact our daily life. Here, an in situ low-voltage-controlled flexible field-effect transistor structure was exploited, which consists of a support layer (mica), functional layer (Fe3O4), and control layer (ionic gel). By applying a low voltage (1.5 V) on the ionic gel, the spin-dynamic properties of the function layer were manipulated and a reversible, nonvolatile 345 Oe ferromagnetic resonance field (Hr) shift was achieved, which corresponds to a large magnetoelectric (ME) coefficient of 230 Oe/V. In addition, a reversible 126 Oe Hrshift (84 Oe/V) was obtained when the layers were bent at curvature radius r= 15 mm. The ME tunability could be attributed to the E-field induced ionic transformation between Fe2+and Fe3+at the interface via electrostatic induction. This sandwich structure shows an excellent and effective ionic gel gating system and paves the way for low-voltage-tunable, nonvolatile, and flexible spintronic devices such as memory devices, sensors, and logical devices.

Yttrium iron garnet (YIG) is of great importance in RF/microwave devices for its low loss, low intrinsic damping, and high permeability. Nevertheless, tuning of YIG-based multiferroics is still a challenge due to its near-zero magnetostriction and the difficulty of building epitaxial interface between ferromagnetic garnet and ferroelectric perovskite phases. In this work, the vertically aligned heterostructure of YIG:BTO/STO(001) with local epitaxial interface between BTO and YIG is well-constructed, where the single crystal BTO pillars are embedded in YIG matrix. A large magnetoelectric coupling effect that drives YIG’s FMR shift up to 512 and 333 Oe (1–2 order greater than those of all state-of-the-art progresses) is obtained through BTO ferroelectric phase changes induced by temperature variation at 295 and 193 K, correspondingly. This record high magnetoelectric tunability of YIG paves a way toward thermal/electrical tunable YIG devices.

Magnetoelectric coupling properties are limited to the substrate clamping effect in traditional ferroelectric/ferromagnetic heterostructures. Here, Fe3O4/BaTiO3nanopillar composites are successfully constructed. The well-ordered BaTiO3nanopillar arrays are prepared through template-assisted pulsed laser deposition. The Fe3O4layer is coated on BaTiO3nanopillar arrays by atomic layer deposition. The nanopillar arrays and heterostructure are confirmed by scanning electron microscopy and transmission electron microscopy. A large thermally driven magnetoelectric coupling coefficient of 395 Oe °C–1near the phase transition of BaTiO3(orthorhombic to rhombohedral) is obtained, indicating a strong strain-induced magnetoelectric coupling effect. The enhanced magnetoelectric coupling effect originated from the reduced substrate clamping effect and increased the interface area in nanopillar structures. This work opens a door toward cutting-edge potential applications in spintronic devices.