Ferroelectric vortex is one of unique domain structures in the hexagonal RMnO 3 (R = Sc, Y, Ho-Lu) systems. This vortex pattern is quite sensitive to crystal imperfections, such as lattice defects and oxygen vacancies, which has been previously observed and studied in a single-crystal structure. Here we report epitaxial growth of hexagonal YMnO 3 thin films on platinum-coated Al 2 O 3 (0001) substrates. High-quality epitaxial YMnO 3 (0001)/Pt(111)/Al 2 O 3 (0001) heterostructures with sharp interfaces have been achieved and characterised by using X-ray diffractometry and transmission electron microscopy. Reversible ferroelectric domain structures have been achieved and observed with well-established piezoresponse hysteresis. Furthermore, the ferroelectric vortex domain patterns with a typical size of~20 nm have been observed, representing a significant progress in the fabrication and exploration of topological vortices in hexagonal RMnO 3 thin films.

In this work, Sm and Sc co-doped Bi 1−x Sm x Fe 1−y Sc y O 3 (x = 0.00-0.20; y = 0.03) ceramics are fabricated by a rapid liquid phase sintering method, in order to develop single-phase multiferroics with large magnetization and polarization. X-ray diffraction and Raman spectroscopic studies reveal that the ceramics are single-phase with a structural transition from rhombohedral to orthorhombic structures near x = 0.15. Electric and magnetic measurement results indicate that the transition significantly enhances the multiferroic properties, which stems from the Sm/Sc doping induced collapse of space-modulated spin structure and internal structural distortion. At an optimized composition of Bi 0.85 Sm 0.15 Fe 0.97 Sc 0.03 O 3 (x = 0.15), a remanent polarization of 16.5 μC cm −2 , a magnetization 0.2020 emu g −1 , and a magnetodielectric effect of 0.46% can be obtained. These results clearly demonstrate a potential application for Sm/Sc doped BiFeO 3 ceramics in the field of multiferroic devices.

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