Epitaxial perovskite rare-earth nickelates and their heterostructures with CMR manganites

Thin films of rare-earth nickelates RNiO₃ (R=Pr, Nd, Sm, Gd) were prepared under a reduced oxygen pressure of <0.02 bar by MOCVD on perovskite substrates. The film–substrate lattice mismatch is critical for the epitaxial stabilization of RNiO₃. Increase of the lattice mismatch or film thickness results in the deposition of rare-earth oxides and NiO instead of RNiO₃. The transport properties of the films on LaAlO₃ were similar to those of the bulk material of the same composition under an applied pressure of 9 kbar. The properties of RNiO₃ films with a sharp metal-to-insulator transition can be effectively tuned by the lattice strain.