Self-Assembled Hexagonal Lu_1–xIn_xFeO₃ Nanopillars Embedded in Orthorhombic Lu_1–xIn_xFeO₃ Nanoparticle Matrixes as Room-Temperature Multiferroic Thin Films for Memory Devices and Spintronic Applications

Self-assembled nanocomposite films containing ferroelectric and ferromagnetic phases have aroused great interest because of their advantages for practical multiferroic applications. However, previously reported self-assembled oxide nanocomposites consist either of a single phase that exhibits various variants or of two different materials. Herein, we demonstrate the growth of Lu1–xInxFeO3 (LIFO) (x = 0.5–0.6) thin films with an unusual self-assembled nanocomposite microstructure containing orthorhombic and hexagonal polymorphs, both of which grow epitaxially with respect to the cubic (001)-SrTiO3 (STO) substrate and which are therefore homoepitaxial with each other. Detailed transmission electron microscopy (TEM) characterization illustrates self-assembled tapered hexagonal (h-LIFO) nanopillars with circular cross section growing perpendicular to the substrate embedded in the orthorhombic (o-LIFO) matrix. The orthorhombic–hexagonal (o–h) mixed-phase LIFO has three domain variants for o-LIFO and the two phases are composed of grains with different sizes. Robust room-temperature multiferroic responses and a huge piezoelectric effect have been demonstrated with huge potentials in various device applications. The realization of the o–h mixed-phase LIFO self-assembled nanocomposite in this work has paved an avenue toward designing and exploring new materials for memory devices and spintronic applications.