BiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.

Physics and Applications of Bismuth Ferrite

Oxide pyrochlores — A review

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

The hybrid two-dimensional (2D) halide perovskites have recently drawn significant interest because they can serve as excellent photoabsorbers in perovskite solar cells. Here we present the large scale synthesis, crystal structure, and optical characterization of the 2D (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1 (n = 1, 2, 3, 4, ∞) perovskites, a family of layered compounds with tunable semiconductor characteristics. These materials consist of well-defined inorganic perovskite layers intercalated with bulky butylammonium cations that act as spacers between these fragments, adopting the crystal structure of the Ruddlesden–Popper type. We find that the perovskite thickness (n) can be synthetically controlled by adjusting the ratio between the spacer cation and the small organic cation, thus allowing the isolation of compounds in pure form and large scale. The orthorhombic crystal structures of (CH3(CH2)3NH3)2(CH3NH3)Pb2I7 (n = 2, Cc2m; a = 8.9470(4), b = 39.347(2) A, c = 8.8589(6)), (CH3(CH2)3NH3)2(CH3NH3)2Pb3I10 (...

http://pubs.acs.org/doi/pdf/10.1021/acs.chemmater.6b00847

Ruddlesden-Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors

Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review, we outline some of the progressive milestones in this stimulating field, especially for those single-phase multiferroics where magnetism and ferroelectricity coexist. First, we highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we summarize various strategies used to combine the two types of order. Special attention is paid to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry; (2) the ferroelectricity originating from the charge-ordered states; and (3) the ferrotoroidic system. Then, we address the elementary excitations such as electromagnons, and the application potentials of multiferroics. Finally, open questions and future research opportunities are proposed.

Multiferroicity: the coupling between magnetic and polarization orders

This paper describes the preparation of the following complex oxide crystals which have not previously been grown by the flux method: FeNbO4, MnWO4, CoWO4, NiWO4, RMn2O5 (R = Er to Sm, and Y), RMnO3 (R = Er to Gd), LaOCl, La2Ti2O71, Bi2Sn2O7, and PbTiP2O8. Single crystal X-ray diffraction data are reported for the latter material, the preparation of which has not previously been reported, and for La2Ti2O7 and Bi2Sn2O71, for which only powder data were previously available. Improved methods for the growth of Mn3O4, LaCoO3, RPO4 (R = Yb to Gd), RCrO3 (R = Lu, Yb), ErOF and NaNbO3 are also reported.

B.M. Wanklyn

Papers

Flux growth of some complex oxide materials

Crystal growth from the flux systems PbOV2O5 and Bi2O3V2O5

Flux growth of rare earth vanadates and phosphates

Mechanical characteristics of flux-grown calcium titanate and nickel titanate crystals

Microhardness, fracture mechanism and dielectric behaviour of flux-grown GdFeO3 single crystals