Critical thickness and orbital ordering in ultrathin La0.7Sr0.3MnO3 films

Detailed analysis of transport, magnetism, and x-ray absorption spectroscopy measurements on ultrathin La_0.7Sr_0.3MnO₃ 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 SrTiO₃ (001) substrate of only three unit cells (∼12Å) . Furthermore, linear-dichroism measurements demonstrate the presence of a preferred (x²-y²) 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.