A Room-Temperature Ferroelectric Ferromagnet in a 1D Tetrahedral Chain Network.

Kang, Kyeong Tae; Roh, Chang Jae; Lim, Jinyoung; Min, Taewon; Lee, Jun Han; Lee, Kyoungjun; Lee, Tae Yoon; Kang, Seunghun et al. · Adv Mater · 2019

basic_science · Level V

Where this comes from

Abstract

Ferroelectricity occurs in crystals with broken spatial inversion symmetry. In conventional perovskite oxides, concerted ionic displacements within a 3D network of transition-metal-oxygen polyhedra (MO<sub>x</sub> ) manifest spontaneous polarization. Meanwhile, some 2D networks of MO<sub>x</sub> foster geometric ferroelectricity with magnetism, owing to the distortion of the polyhedra. Because of the fundamentally different mechanism of ferroelectricity in a 2D network, one can further challenge an uncharted mechanism of ferroelectricity in a 1D channel of MO<sub>x</sub> and estimate its feasibility. Here, ferroelectricity and coupled ferromagnetism in a 1D FeO<sub>4</sub> tetrahedral chain network of a brownmillerite SrFeO<sub>2.5</sub> epitaxial thin film are presented. The result provides a new paradigm for designing low-dimensional MO<sub>x</sub> networks, which is expected to benefit the realization of macroscopic ferro-ordering materials including ferroelectric ferromagnets.