[GS_C_MS] Symmetry Engineering of Uniaxial In-Plane Ferroic Orders in Oxide Heterostructures
ABSTRACT
Controlling the orientation and symmetry of ferroic order parameters is essential for developing thin-film electronic and spintronic devices. Conventional ferroelectric devices predominantly exploit out-of-plane polarization, and Hall-based electrical detection of magnetism is also generally sensitive to the out-of-plane magnetization component. Realizing and controlling uniaxial in-plane ferroic orders therefore provides opportunities for planar device architectures, but requires precise manipulation of the underlying crystallographic and interfacial symmetries. In this talk, we present two representative examples demonstrating how symmetry engineering can be employed to control in-plane ferroic orders in oxide heterostructures.
First, by engineering the interface between Hf0.5Zr0.5O2 (HZO) and perovskite oxides, we control the HZO structure from the conventional (111)-oriented multidomain configuration to an unconventional (100)-oriented single-domain orthorhombic phase. The resulting HZO(100) films exhibit robust uniaxial in-plane ferroelectric polarization, which persists down to a thickness of 1.0 nm, together with an ultralow coercive field of ~0.5 MV/cm. This HZO(100) phase is stabilized by a staggered interfacial reconstruction.
Second, we employ interfacial symmetry engineering to realize an in-plane anomalous Hall effect (IP-AHE) in epitaxial CaRuO3/La2/3Ca1/3MnO3/CaRuO3 heterostructures. Interfacial octahedral coupling induces a monoclinic-like distortion and breaks mirror symmetries in the ferromagnetic La2/3Ca1/3MnO3 layer. Together with its uniaxial in-plane magnetic anisotropy, this symmetry breaking activates a robust IP-AHE that directly tracks the reversal of in-plane magnetization. Moreover, ionic-liquid gating reversibly reconfigures the interfacial symmetry through protonation of CaRuO3, enabling wide-range electrical modulation and reversible ON/OFF switching of the IP-AHE.
Together, these studies demonstrate that interfacial and crystallographic symmetry engineering provides a powerful route to manipulate in-plane ferroic orders and their associated electrical responses, offering new opportunities for planar-geometry ferroelectric and spintronic functionalities.
