The aim of the present work is an atomic scale characterization of the ${\mathrm{SrTiO}}_3/{\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_3$ interface involved in ${\mathrm{C}\mathrm{o}/\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3/{\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_3$ tunnel junctions. Our high-resolution transmission electron microscopy experiments show the quality of the pseudo-morphic growth of ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_3$ (LSMO) and ${\mathrm{SrTiO}}_3$ (STO), but do not allow us to determine the termination of LSMO. On the other hand, we have carried out an energy-loss near-edge structure study of the ${\mathrm{Mn}}_{2p}$ and ${\mathrm{O}}_{1s}$ edges. The main result is that the valence of Mn keeps its intrinsic value of the bulk material till the last ${\mathrm{MnO}}_2$ layers at the interface, which is consistent with the observation of magnetoresistance up to practically the Curie temperature of bulk LSMO in our junctions. These results suggest a ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}\mathrm{O}$ termination of LSMO.

• Received 9 October 2001

DOI:https://doi.org/10.1103/PhysRevB.66.014417