Ultraflexible and Malleable Fe/BaTiO₃ Multiferroic Heterostructures for Functional Devices

Abstract

The high demand for flexible spintronics based on multiferroic heterostructures makes growing high‐quality flexible, functional oxides urgently, in which needs to be deposited on lattice‐matched substrates. In this paper, ultraflexible and malleable iron (Fe)/BaTiO3 (BTO) multiferroic heterostructures are demonstrated, showing a perfect crystallinity and hetero‐epitaxial growth. In terms of performance, they indicate good multiferroic properties and excellent bending tunability, as well as obvious magnetoelectric (ME) coupling effect. During the phase transformation from the rhombohedral phase to the orthorhombic phase of BTO layers in the heating process, a large ME coupling coefficient of 120 Oe °C−1 along the out‐of‐plane direction is obtained. This value keeps consistent in the phase‐field simulation of magnetic domain evolution, in which the biaxial compressive strain induced‐magnetoelastic anisotropy facilitates the magnetic easy axis of Fe layers to the [110] or [–1–10] direction. Besides, ultraflexible Fe/BTO heterostructures are found to have a 690 Oe ferromagnetic resonance (FMR) field shift along the out‐of‐plane direction under the flexible tuning (R = 5 mm). This work should pave a way toward flexible spintronic and functional devices with fast speed, portability, and low energy consumption.

Recent Progress in Flexible Multiferroics

“…Freestanding BFO films were lifted by dissolving the SAO sacrificial layer in deionized water with mechanical support from PDMS tape or silicon-coated PET and then transferred onto the desired substrates. Furthermore, Zhao et al [40] prepared freestanding Fe/BaTiO 3 (BTO) multiferroic heterostructures by using the SAO sacrificial layer. Pesquera et al [41] reported the fabrication of multiferroic LSMO/0.68Pb(Mg 1/ 3 Nb 2/3 )O 3 -0.32PbTiO 3 (PMN-PT) heterostructures by the epitaxial transfer technique using SrRuO 3 as a sacrificial layer.…”

“…Furthermore, Feng et al [49] predicted that the magnetoelectrical properties strongly improved in the case of LSMO/BFO superlattice. Zhao et al [40] demonstrated the growth of multiferroic Fe/BaTiO 3 (BTO) heterostructures by using the PLD technique, followed by transfer of the Fe/BTO functional layer on PDMS substrates. The flexible Fe/BTO/PDMS heterostructures exhibited good ferroelectric and ferromagnetic behavior with a bending radius of 5 mm.…”

2–2 Type PVDF‐Based Composites Interlayered by Epitaxial (111)‐Oriented BTO Films for High Energy Storage Density

“…[ 28–31 ] In this way, we obtained the freestanding epitaxial (100)‐oriented BaTiO 3 (BTO) films remaining excellent ferroelectricity and flexibility. [ 32,33 ] However, (100)‐oriented BTO films do not possess strong E b as (111)‐oriented BTO films do. This is because the (111)‐oriented BTO exhibits a much lower electrostrictive coefficient, resulting in a reduced electric‐field‐induced strain along the direction of the electric field.…”

Flexible Multiferroic Heterostructure Based on Freestanding Single‐Crystalline BaTiO3 Membranes for Spintronic Devices

“…Flexible spintronic materials have been studied systematically for the integration of conventional magnetic sensors such as anisotropic magnetoresistive coupling effect as well as excellent flexibility. [9] Although freestanding single-crystalline ferroelectric and multiferroic membranes have exhibited extraordinary flexibility, freestanding single-crystalline multiferroic membranes with PMA remains unexplored.…”