Investigation on crystal growth and characterization of RMnO3 single crystals

Abstract

The general motivation behind the research in the thesis is to newlineunderstand the crystal and magnetic properties which in turn give a clearer newlineideal for magnetoelectric coupling in several multiferroics. newlineChapter 1 describes a brief overview of a multiferroic and the newlinemotivation for carrying out the present investigation are given. newlineChapter 2 gives the crystal growth technique used for preparation newlineof single crystals. A concise overview of the basic experimental technique newlineemployed in this thesis work is given. newlineChapter 3 investigates the structural transition due to the growth newlineatmosphere and Y3+ substitution in DyMnO3 single crystals. Large size single newlinecrystals of DyMnO3, YMnO3 and their solid solutions, Dy1-xYxMnO3, have newlinebeen grown by the optical floating zone technique. It is shown that pristine newlineDyMnO3 crystals grown in air atmosphere correspond to the orthorhombic newlinephase in the Pnma space group symmetry (SGS) while the argon atmosphere newlinegrowth leads to the hexagonal phase in the P63cm SGS. The crystals grown in newlineair atmosphere for the composition range 0.10 and#8804; x and#8804; 0.50 show coexistence of newlineorthorhombic and hexagonal phases with increasing hexagonal (h-) phase newlinefraction until at x~0.60, the orthorhombic phase completely transforms to the newlinehexagonal phase even in the air atmosphere. On the otherhand, all the crystals newlinegrown in argon atmosphere correspond to the hexagonal phase only. Our newlineRietveld refinements using X-ray powder diffraction (XRPD) data on newlinepowders obtained after crushing the crystals further confirm the hexagonal newlinestructure in the P63cm SGS for all crystals grown in argon atmosphere. newline