Strain effect on transport properties of SrRuO ₃ films grown by laser MBE

Abstract:

Transport properties of SrRuO₃ thin films were studied as a function of the epitaxial strain. SrRuO₃ films were grown on (100) SrTiO₃ substrates by the Pulsed Laser Deposition technique equipped with Reflection High Energy Electrons Diffraction (RHEED). Samples thickness has been varied from a few unit cells to above 1000 Å while monitoring RHEED intensity oscillations. In thicker films epitaxial strain was found to be progressively relaxed. SrRuO₃ relaxed films (thickness 1000 Å) show metallic behavior for the whole temperature range with a ferromagnetic ordering at about 150 K. For thinner films, ferromagnetic ordering occurs at progressively lower temperatures, until in films thinner than 400 Å it disappears. Films thinner than 80 Å show a semiconducting behavior at low temperatures. Our results provide direct evidence of the crucial role of the strain effect for conducting and magnetic properties of SrRuO₃.