Electrical resistivity anomaly in (Pr1−yMy)1−xCaxCoO3 epitaxial films (M=Y, Gd) fabricated by pulsed laser deposition

(Pr1−yMy)1−xCaxCoO3 epitaxial films (M=Y, Gd) have been successfully fabricated by pulsed laser deposition on the single crystal substrates with different lattice constant. The polycrystalline bulk of this material shows a first-order metal-insulator (MI) transition below the critical temperature. Although ρ(T) of all the as-grown films shows a semiconducting behavior at entire temperature range, an anomalous ρ(T) upturn with wide hysteresis can be clearly seen for the film grown on the SrLaAlO4 (SLAO) substrate, which applied the in-plane compressive stress to the film. Such anomaly in ρ(T) is interpreted as a sign of the first-order phase transition related with the spin-state (SS) transition, which was observed in the polycrystalline bulk