Structure and Properties Modulation of RMnO3 Multiferroic Materials by Average Ionic Radius at A-Site

The effects of internal chemical pressure produced by A-site ionic radius were investigated for the Ho1-xDyxMnO3 system. It is found that the hexagonal HoMnO3 is gradually transformed to orthorhombic perovskite structure as reducing A-site ion size, forming three regions which contain pure hexagonal phase, mixture of hexagonal and orthorhombic phases and pure orthorhombic phase respectively. Using Rietveld method, the crystal structures were refined, and moreover, the correlations between lattice parameters and unit cell volume as a function of Dy3+ ion content x were obtained. The properties of the temperature dependence of the magnetization and specific heat were also studied. It is suggested that Dy3+ doping would increase the ordering temperature T2 of rare earth elements.