Disorder effects in epitaxial thin films of (La,Ca)MnO3

Abstract

We have investigated as-grown sputtered films of ${\mathrm{La}}_{\mathrm{0.7}}{\mathrm{Ca}}_{\mathrm{0.3}}{\mathrm{MnO}}_{\mathrm{3}}$ in a thickness range between 5 and 200 nm on ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrates. The films are epitaxial, strained, and smooth. All films order magnetically around 175 K. Very thin films show full magnetization at low temperatures, but the temperature of the metal–insulator transition is appreciably lower than the magnetic ordering temperature. In thick films, the magnetization is much lower than expected. Both effects are probably related to structural disorder as found by transmission electron microscopy.