Linear dichroism (LD) in x-ray absorption, diffraction, transport, and magnetization measurements on thin ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ films grown on different substrates, allow identification of a peculiar interface effect, related just to the presence of the interface. We report the LD signature of preferential $3d-e_g(3z^2-r^2)$ occupation at the interface, suppressing the double exchange mechanism. This surface orbital reconstruction is opposite to that favored by residual strain and is independent of dipolar fields, the chemical nature of the substrate and the presence of capping layers.

Strain induced anisotropy in the electronic properties of ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$ thin films was investigated by x-ray absorption spectroscopy at the Mn $2p$ and O $1s$ edges. Films on (100) $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ and (100) $\mathrm{La}\mathrm{Al}{\mathrm{O}}_3$ substrates were grown by pulsed laser deposition with in situ reflection high energy electron diffraction diagnostic. At both absorption edges, clear features related to different anisotropic lattice strain effects as a function of the substrate were observed. On the average a negative (positive) linear dichroism was obtained for films grown under in-plane tensile (compressive) epitaxial strain conditions. Indeed, the structural macroscopic distortion induced by the substrate is responsible of the octahedra distortions with the resulting stabilization of $x^2\text{−}{y}^2$ $\left(3z^2\text{−}{r}^2\right)$ orbitals. Enhanced linear dichroism at the Mn $2p$ edge in very thin films, only a few unit cells thick, is in agreement with a fully strained state which favors the formation of orbital ordered phase regions.

In this paper, we illustrate an approach to discriminate between epitaxial strain and other factors responsible for the decrease of the metal–insulator transition temperature (TP) in thin La0.7Sr0.3MnO3 films grown by pulsed laser deposition. Using this approach, we have estimated the effect of the biaxial strain on TP. Ultrathin films, independent of epitaxial strain, do not show any metal–insulator transition over the full temperature range. This finding confirms the existence of an interface dead layer. The strain-independent decrease in TP, relative to its bulk value, observed for a much wider thickness range (up to about 1000Å) can most likely be attributed to oxygen deficiency.