Structure, Physical Properties, Charge Ordering Research On La_2-xSr_xMnO₄ And Primary Research On New Superconductor Na_xCoO₂·yH₂O By Electrochemical Method

1. Structure, Physical Properties and Charge Ordering in La2-xSrxMnO4 (1.125≤x≤2.0)。Intensive studies have been conducted on colossal magnetoresistance (CMR) material with AMnO3 (A=Alkaline earth and rare earth elements) perovskite structure since 1993, and comparatively less attention was focused on their close derivatives with the K2NiF4 structure showing a quasi-two dimensional character. In this paper, a systematical research was done on the La2-xSrxMnO4 material with the K2NiF4 structure. Structural measurements have revealed the nonlinear changes of lattice parameters in the manganites La2-xSrxMnO4 with the increase of Sr content, and these changes can be well understood by means of interactions among the charge, crystal lattice and the orbital degree of freedom in this system. A probably spin-glass transition was detected for the first time in the x=1.75 sample at the temperature of around 44K. Fundamental properties of charge ordering appearing in the range of 1.5≤x≤1.75 have been observed at low-temperatures and interpreted in terms of the Mn3+-dz2 orbital ordering.2. In order to control the parameters (including voltage, current, etc.) in electrochemical experiment precisely, The software PSMMCP (Power Supply and MultiMeter Controlling Program) was developed. 3. NaxCoO2·yH2O was a new superconductor reported firstly in March 2003. Although the Tc was only about 5K, it has attracted much attention for theoretical importance because there is no Cu-O layer in it. Primary research was done on it by electrochemical method with the software PSMMCP. Primary result was obtained and the more research is under way.