Controlling Spin Textures in Multiferroic Oxide: from Strain Engineering to Voltage Switching

With Moore’s law approaching its physical limit, beyond-CMOS concepts are needed to address the rising power demands of Internet of Things (IoT) and artificial intelligence (AI) technologies [1]. Magnetoelectric spin-orbit (MESO) logic offers a promising route by harnessing electric-field control of magnetism via multiferroics [2]. The room-temperature multiferroic BiFeO₃ is central to this approach as a magnetoelectric medium due to the coupling between its antiferromagnetic spin cycloid and ferroelectric polarization. Yet, the coexistence of multiple ferroelectric variants [3,4] leads to complex switching pathways. Achieving deterministic, energy-efficient operation therefore requires stabilizing ferroelectric-domain-free, single-variant BiFeO₃ suitable for reproducible magnetoelectric control.

In this talk, I will present two parts. First, I will show how we simplified the multiferroic landscape of epitaxial BiFeO₃ thin films by engineering them into single-domain variants through anisotropic-strain strategies. These single-domain systems allowed us to identify the fundamental limit of the magnetoelectric interaction and enabled narrow-band THz emission from this configuration [5-7]. The second part revolves around the deterministic electric-field control of ferroelectric polarization in substrate-vicinality-driven single ferroelectric variants (P) as well as single spin-cycloid propagation directions (k). In these heterostructures, we achieve significant, nonvolatile, and deterministic control of the magnetic state [8]. This heterostructure provides a promising platform for magnetoelectric-based devices, advancing the development of MESO technology toward practical applications.