Detailed analysis of transport, magnetism, and x-ray absorption spectroscopy measurements on ultrathin ${\text{La}}_{0.7}{\text{Sr}}_{0.3}{\text{MnO}}_3$ films with thicknesses from 3 to 70 unit cells resulted in the identification of a lower critical thickness for a nonmetallic nonferromagnetic layer at the interface with the ${\text{SrTiO}}_3$ (001) substrate of only three unit cells $\left(\sim 12\text{Å}\right)$. Furthermore, linear-dichroism measurements demonstrate the presence of a preferred $\left(x^2\text{−}{y}^2\right)$ in-plane orbital ordering for all layer thicknesses without any orbital reconstruction at the interface. A crucial requirement for the accurate study of these ultrathin films is a controlled growth process, offering the coexistence of layer-by-layer growth and bulklike magnetic/transport properties.

• Received 2 July 2008

DOI:https://doi.org/10.1103/PhysRevB.78.094413