Potential advantage of multiple alkali metal doped KNbO3 single crystals

Potassium niobate crystal KNbO3 (KN) is a well-known crystal for lead free piezoelectric or nonlinear optical applications. The KN crystal has been studied in both single crystal form and in thin film form which has resulted in many review articles being published. In order to exceed the KN crystal, it is important to study KN phase forming and doping effects on the K site. This article summarizes the authors\u27 study towards a multiple alkali metal doped KN crystal and related single crystals briefly from the viewpoint of crystal growth

Ferroelectric and mutiferroic study of bismuth ferrite from the viewpoint of materials science

Ferroelectric and mutiferroic materials have been studied from the viewpoint of pure and applied physics. For the applications, a study from the viewpoint of materials science will be important in the future. Examples of materials science study are substitution of elements, selection of substrate in thin films and in-situ observation. Nano-scale domain configurations of multiferroic BiFeO3 thin films and their dynamic response to the externally applied fields have been investigated by piezoresponse force microscopy. High-resolution piezoresponse images reveal that nano-scale domain walls are approximately with ~2 nm in width. In this article, we focus on BiFeO3 as mutiferroic materials and as ferroelectric materials. We will present our results about electric and magnetic properties, and scanning probe microscopy observations. Local polarization reversal and retention behavior will also be presented and discussed

Density of states, magnetic and transport properties of Nd doped two dimensional perovskite compound Sr2CoO4

Structures, transport, magnetic properties, and first principle calculation results will be reported for the two dimensional layered structured perovskite compounds Sr2-xNdxCoO4 (x = 0.5, 0.75, 1, 1.25). Structure refinement results revealed that these compounds crystallized in K2NiF4-type structures with space group I4/mmm. The temperature dependence of resistivity showed semiconductor like behavior for these samples. It was found that the lattice parameter c decreases as the doping level x increases. The compounds exhibited a paramagnetic to ferromagnetic transition at temperatures of about 170, 125 K for the x = 1 and 0.75 samples, respectively. The temperature dependence of resistivity for the samples can be well fitted by the 2D variable hoping (VRH) model rho = rho(o) exp(T-0/T)(1/3) (where rho(o) is a material specific characteristic conductance, with unit Omega(-1), T-0 is a material specific characteristic temperature in K) over the whole measured temperature range. First principles calculations indicated that the Nd doped Sr2CoO4 compounds show high spin polarization. (C) 2012 American Institute of Physics. [doi:10.1063/1.3672825