Structure and magnetic investigations of Ca1-xYxMnO3 (x=0, 0.1, 0.2, 0.3) and Mn4+/Mn3+ relation analysis

Abstract

Structure and magnetic features of nanostructured materials with general formula Ca1-xYxMnO3 (x = 0; 0.1; 0.2; 0.3) were investigated. Goldschmidt tolerance factor, Gt and global instability index, GII were calculated for Ca1-xYxMnO3 (x = 0, 0.25, 0.5, 0.75, 1) using the software SPuDS (Structure Prediction Diagnostic Software). According to these two parameters possibility of forming perovskite structure type for Ca1-xYxMnO3 solid solution was analyzed. Substitution of Y3+ for Ca2+ provokes reduction of equivalent amount Mn4+ into Mn3+, the presence of which is a reason for many interesting magnetic, transport and structural features of doped CaMnO3. Crystal structure refinement was carried out using Rietveld analysis. Ca1-xYxMnO3 (x = 0; 0.1; 0.2; 0.3) has an orthorombic, Pnma space group that, according to Glazer´s classification belongs to a-b+a- tilt system. Influence of Y amount on Mn-O bond angles and distances, tilting of MnO6 octahedra around all three axes and octahedra deformation were analyzed. Bond valence calculations (BVC) were performed to determine Mn valence state. Using EPR (electron paramagnetic resonance) magnetic measurements were performed and magnetic properties of solid solutions, orthorombicity degree of unit cell, as well as Mn4+/Mn3+ cations ratio in position B were analyzed. Microstructure size-strain analysis was performed and these results are in nanometric range which is confirmed by TEM images.

Keywords

• nanostructured materials
• rietveld analysis
• BVC calculations
• magnetic properties