Exploration of new ferroic (ferroelectric, ferromagnetic or ferroelastic) materials continues to be a central theme in condensed matter physics and to drive advances in key areas of technology. Here, using thin-film composition spreads, we have mapped the functional phase diagram of the Ni-Mn-Ga system whose Heusler composition Ni(2)MnGa is a well known ferromagnetic shape-memory alloy. A characterization technique that allows detection of martensitic transitions by visual inspection was combined with quantitative magnetization mapping using scanning SQUID (superconducting quantum interference device) microscopy. We find that a large, previously unexplored region outside the Heusler composition contains reversible martensites that are also ferromagnetic. A clear relationship between magnetization and the martensitic transition temperature is observed, revealing a strong thermodynamical coupling between magnetism and martensitic instability across a large fraction of the phase diagram.

This paper presents the report on the piezophotocatalysis of single-crystal rhombohedral ZnSnO 3 nanowires. An essential feature of this study was the close coupling of the functions of piezophototronics (semiconductors, piezoelectricity, and photonics) and photocatalysis for achieving synergistic catalytic performance. Vertically aligned lead-free noncentrosymmetric high purity ZnSnO 3 nanowires (LiNbO 3 -type, R3c) were fabricated using a two-step hydrothermal reaction. The piezophototronic effect was demonstrated to substantially enhance the photocatalytic activity (by approximately 27%) by modulating the piezopotentials across the ZnSnO 3 nanowires. The enhancement was attributed to reduced recombination of photogenerated electron-hole pairs and enhanced mobility of these pairs resulting from the energy band distortion caused by applied stresses.

We report on the synthesis of PbTiO3–CoFe2O4 multiferroic nanocomposites and continuous tuning of their ferroelectric and magnetic properties as a function of the average composition on thin-film composition spreads. The highest dielectric constant and nonlinear dielectric signal was observed at (PbTiO3)85–(CoFe2O4)15, where robust magnetism was also observed. Transmission electron microscopy revealed a pancake-shaped epitaxial nanostructure of PbTiO3 on the order of 30 nm embedded in the matrix of CoFe2O4 at this composition. Composition dependent ferroics properties observed here indicate that there is considerable interdiffusion of cations into each other.

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