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.

The multilayered composite films combining antiferroelectric (AFE) Pb0.97La0.02(Zr0.95Ti0.05)O3 (PLZT) with paraelectric (PE) SrTiO3 (STO) have been fabricated by the sol–gel method, and their ferroelectric and energy storage performances were carefully investigated. It was revealed that both the dielectric breakdown strength (Eb) and the maximum polarization (Pm) in the multilayered composite films are increased. Consequently, an ultra-high and recoverable energy storage density (Wre) of ∼101 J/cm3 and a high efficiency (η) of ∼62% were achieved in the composite film with an 18 wt. % STO content. The enhanced Wre in the multilayered composite is attributed to the internal-strain release of the PLZT layers and charge blocking by the STO layers with significantly enhanced Eb. The results suggest an effective way of improving the energy storage performances by combining AFE PLZT and PE STO.

In this work, we investigated the nanoscale conduction and charge transport characteristics of epitaxial VO2 thin films around the metal-insulator transition (MIT) using the Hall transport measurement and conduction atomic force microscopy. Unlike the conventional oxides, the VO2 thin films show unique transport characteristics. First, the dominant carrier type shows a critical change from electron to hole during the MIT sequence (cooling sequence) or from hole to electron during the reverse MIT sequence (heating sequence). Second, the carrier density measured during the MIT sequence is higher than that measured during the reverse MIT sequence, evidenced with a clear thermal hysteresis. Third, the volume fraction (area percentage) of the nanoscale high-conduction phase also shows a thermal hysteresis, evidenced with a larger volume fraction of the high-conduction region in the MIT sequence than the reverse MIT sequence. The first-principles calculations indicate that the dominant carrier is the hole in the monoclinic phase, while it is the electron in the rutile phase, suggesting that the unique charge transport characteristics are attributed to the structural phase transition. Our work provides a deep insight into the nanoscale conduction and charge transports in VO2 thin films.

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The spin ordering magnetic structures of orthorhombic YMnO3 subjected to uniaxial strain have been investigated using first-principles calculations based on density functional theory. On applying compressive uniaxial strain of −0.8% along the b orientation, the spin ordering magnetic structure is predicted to change from E-type to A-type antiferromagnetic orderings. The structure analysis also reveals that the uniaxial strain has a dramatic influence on the Mn-O bond lengths and Mn-O-Mn bond angles, allowing the gradual suppression of the alternation of the long and short Mn-O-Mn bonds in the ab plane. These changes present very interesting possibilities for engineering the spin ordering along with ferroelectric property in orthorhombic YMnO3.