Solid-state dielectric energy storage is the most attractive and feasible way to store and release high power energy compared to chemical batteries and electrochemical super-capacitors.

The complex metal oxides Ni 2 InSbO 6 (NISO) and Ni 2 ScSbO 6 (NSSO) have been prepared in the form of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties of the compounds were investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric, and magnetic measurements. The compounds adopt a trigonal structure, space group R3, of the corundum related Ni 3 TeO 6 (NTO) type. Only one of the octahedral Ni positions (Ni(2)) of the NTO structure was found to be occupied by In (Sc). NTO has noncentrosymmetric structure and is ferroelectric below 1000 K; dielectric and second harmonic measurements suggest that also NISO and NSSO are correspondingly ferroelectric. Magnetization measurements signified antiferromagnetic ordering below T N = 60 K (NSSO) and 76 K (NISO). The magnetic structure is formed by two antiferromagnetically coupled incommensurate helices with the spiral axis along the b-axis and propagation vector k = [0, k y ,0] with k y = 0.036(1) (NSSO) and k y = 0.029(1) (NISO). The observed structural and magnetic properties of NISO and NSSO are discussed and compared with those of NTO.

The complex metal oxide Mn3TeO6 exhibits a corundum related structure and has been prepared both in forms of single crystals by chemical transport reactions and of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric and magnetic measurements. At room temperature this compound adopts a trigonal structure, space group R3 with a = 8.8679(1) {\AA}, c = 10.6727(2) {\AA}. A long-range magnetically ordered state is identified below 23 K. An unexpected feature of this magnetic structure is several types of Mn-chains. Under the action of the incommensurate magnetic propagation vector k = [0, 0, 0.4302(1)] the unique Mn site is split into two magnetically different orbits. One orbit forms a perfect helix with the spiral axis along the c-axis while the other orbit has a sine wave character along the c-axis.Comment: PDF; 16 pages, 6 figure

A complex magnetic order of the multiferroic compound Co 3 TeO 6 has been revealed by neutron powder diffraction studies on ceramics and crushed single crystals. The compound adopts a monoclinic structure (s.g. C2/c) in the studied temperature range 2 K -300 K but exhibits successive antiferromagnetic transitions at low temperature. Incommensurate antiferromagnetic order with the propagation vector k 1 = (0, 0.485, 0.055) sets in at 26 K. A transition to a second antiferromagnetic structure with k 2 = (0, 0, 0) takes place at 21.1 K. Moreover, a transition to a commensurate antiferromagnetic structure with k 3 = (0, 0.5, 0.25) occurs at 17.4 K. The magnetic structures have been determined by neutron powder diffraction using group theory analysis as a preliminary tool. Different coordinations of the Co 2+ ions involved in the low-symmetry C2/c structure of Co 3 TeO 6 render the exchange-interaction network very complex by itself. The observed magnetic phase transformations are interpreted as an evidence of competing magnetic interactions. The temperature dependent changes in the magnetic structure, derived from refinements of highresolution neutron data, are discussed and possible mechanisms connected with the spin reorientations are described. 1.IntroductionThe origin and understanding of the coupling phenomena between different physical properties within a material is a central subject of solid state science. A great deal of theoretical and experimental attention in this field is currently focused on the coupling between magnetism and ferroelectricity, as can be encountered in the so-called multiferroics [1,2]. These compounds present opportunities for a wide range of potential applications [3,4] in addition to the fact that the fundamental physics of multiferroic materials is rich and fascinating [5][6][7][8]. The coexistence of ferromagnetism and ferroelectricity is difficult to achieve for many reasons [2,9] and only very few multiferroic materials are known [5]. First, and most fundamentally, the cations which are responsible for the electric polarization in conventional ferroelectrics have filled d-electron shells. In contrast, ferromagnetism requires unpaired electrons, which in many materials are provided by d electrons of transition metal ions. Therefore the coexistence of the two phenomena, although not prohibited by any physical law or symmetry consideration, is discouraged by the local chemistry that favors one or the other but not both. In practice, alternative mechanisms for introducing both the polar ion displacements and the spin ordering are still needed. Theory gives us a good guide in what type of materials we can expect a large coupling effect. There are several important conclusions that we can draw regarding future directions of multiferroic research [2,5,9].1 However, experimental activity has been limited due to a lack of novel materials. Existing multiferroic compounds belong to different crystallographic classes, and although some general rules governing their behaviour are already estab...

Silver niobate (AgNbO3)-based dielectric materials show great application potential in pulse power energy storage systems due to their high energy storage density.

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