Effect Of Epitaxial Strain On Small-Polaron Hopping Conduction In Pr-0.7(Ca0.6sr0.4)(0.3)Mno3 Thin Films

We investigated the epitaxial strain effect on the small-polaron hopping conduction properties in Pr-0.7(Ca,Sr)(0.3)MnO3 (PCSMO) films. An increase in the carrier localization, as evidenced by the enhancement of the small-polaron activation energy E-A in the high temperature region, was obtained by increasing the epitaxial lattice strain in either the tensile or compressive strained film. Furthermore, it was found that the magnitude of E-A, and thus the carrier localization, strongly depends on the sign of the lattice strain, which explains the diverse percolative transport behaviors in PCSMO films with different types of strains. Meanwhile, similar dependencies on the strain of the films were also obtained for the electron-phonon interaction, characterized by the calculated small-polaron coupling constant. Our results reveal that the type of lattice strain plays a crucial role in determining the degree of localization of charge carriers and the electron-phonon coupling strength, which is important for understanding the lattice strain-induced various novel properties related to phase separation and percolation behaviors. (C) 2015 AIP Publishing LLC.