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Strong Stark splitting, which is independent of the R-ions replacement, is observed through the photoluminescence investigation of electronic ferroelectric [Er.sub.1][Yb.sub.x][Fe.sub.2][O.sub.4]. The unusually large Stark splitting at visible range has shown the existence of strong local field originated from the W-layer in the charge-frustrated Er[Fe.sub.2][O.sub.4].

Abstract: C-axis orientated LuFe2O4 thin films on (001) sapphire substrates are epitaxially deposited by pulsed-laser deposition. Temperature-dependent resistance characterization reveals the ferrimagnetic transition at 237K and charge-ordering transition at 340K in the film. Importantly, the dielectric constant of the film can be significantly changed by both electric and magnetic fields. The dielectric tunability reaches 35% when an electric field of 5V is applied, while this value reduces to 20% and 15%, respectively, when a magnetic field of 0.83T is applied perpendicular and parallel to the film normal direction. This suggests a magnetically controlled dielectric tunability and strong magnetoelectric coupling, and is therefore promising for tunable device applications in film form. [Copyright &y& Elsevier]

Abstract: A new inverse spinel ScMn2O4 has been synthesized and characterized by measurements of structural and physical properties. The crystal structure of ScMn2O4, similar with the spinel Mn3O4, is made up of Mn2+ located at tetrahedral site and Mn3+/Sc3+ ions randomly located at the octahedral site. Experimental results of magnetic susceptibility and heat capacity demonstrate that ScMn2O4 undergoes a ferrimagnetic phase transition at the temperature of about 58K. Extensive analyses on the data obtained from structural refinement, electronic structural calculation and EELS spectra measurement suggests that substitution of Sc for Mn in MnO6 octahedron could greatly suppress Jahn–Teller distortions in comparison with what observed in Mn3O4. [Copyright &y& Elsevier]

Abstract: Ferroelectric and piezoelectric properties of layered Lu2Fe2.1Mn0.9O7 ceramic have been investigated by temperature-dependent piezoresponse force microcopy (PFM) and dielectric measurements. The PFM results illustrate the existence of piezoelectric properties and ferroelectric phase transition temperature of about 90°C at which the piezoelectricity vanishes. This transition temperature is manifested by the appearance of a shoulder at about 90°C in the temperature-dependent dielectric curve of the poled sample. A macro-to-micro domain transition is proposed to explain this ferroelectric phase transition. Besides, the ferroelectric properties of the Lu2Fe2.1Mn0.9O7 ceramic are further demonstrated by the polarization-electric field hysteresis (P–E) loop measurement. [Copyright &y& Elsevier]

Abstract: Polycrystalline and single crystalline samples of CaFe2As2 were prepared by using different fabrication routes. These samples show evident differences in both phase transition temperatures and transport properties depending on fabrication conditions. TEM observations reveal a rich variety of structural phenomena in these materials, such as a tweed-like pattern in self-flux samples, a structural modulation along the 〈110〉tetra direction in the polycrystalline sample, and complex dislocation networks in the Sn-flux samples. Careful analysis shows that the twinning domains arising from the tetragonal-to-orthorhombic phase transition belong to the δ-type. [Copyright &y& Elsevier]

Abstract: SrMn2As2 single crystals were grown by the Sn flux method. Structural features of these crystals were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that the single crystal has a rhombohedral structure and grows along the c-axis direction. The microstructure and layered structural features of this material have been examined by SEM and high-resolution TEM observations. The measurements of in-plane resistivity as a function of temperature demonstrate that SrMn2As2 undergoes a phase transition of semiconductor–insulator at a low temperature; the active energies are estimated to be Δ=0.64 and 0.29eV for two distinct regions. Magnetic measurements show a clear antiferromagnetic (AFM) transition at about T N =125K. Therefore, the SrMn2As2 material is an AFM insulator at low temperatures and could be a potential parent compound for superconductors. [Copyright &y& Elsevier]