Epitaxial stabilization and structural properties of REMnO3 (RE=Dy,Gd,Sm) compounds in a layered, hexagonal ABO3 structure

Abstract

$\mathrm{RE}\mathrm{Mn}{\mathrm{O}}_3$ $(\mathrm{RE}=\mathrm{Dy},\mathrm{Gd},\mathrm{Sm})$ films were deposited on (110) surfaces of single crystalline hexagonal $\left(h\text{-}\right)\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_3$ . These films adopted the metastable multiferroic $h\text{-}\mathrm{RE}\mathrm{Mn}{\mathrm{O}}_3$ structure instead of the stable perovskite structure. Sharp $\left(hh0\right)$ diffraction peaks with narrow rocking curves were found for all films. The peak widths increased with increasing size of the rare-earth cation. The $c$ -axis/$a$ -axis lattice parameter decreased/increased monotonically with increasing rare-earth size for these epitaxial films. All films exhibited the following epitaxial relationship ${\left\{110\right\}}_{\mathrm{RE}\mathrm{Mn}{\mathrm{O}}_3}\Vert {\left\{110\right\}}_{\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_3};{⟨1\overline{1}0⟩}_{\mathrm{RE}\mathrm{Mn}{\mathrm{O}}_3}\Vert {⟨1\overline{1}0⟩}_{\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_3}$ . The single-phase hexagonal films were kinetically robust against back transformation to the stable perovskite structure even to thicknesses of $50\mathrm{nm}$ .