Strain-controlled electrical and magnetic properties of SrRuO₃thin films with Sr₃Al₂O₆buffer layers

SrRuO3 (SRO) thin films have been grown on a (001)-oriented SrTiO3 substrate with Sr3Al2O6 (SAO) buffer layers using pulsed laser deposition. X-ray diffraction results reveal that the epitaxial strain of SRO changes from compressive to relaxed or tensile ones by tuning the thickness of the SAO buffer layer (tSAO). We have demonstrated that the variation of strain has a strong influence on the microstructure and electrical and magnetic properties of SRO. When tSAO < 10 nm, the epitaxial strain is relaxed and the SRO film possesses higher Curie temperature resembling that of SRO bulk. Upon further increasing tSAO ≥ 10 nm, the SRO films are subjected to tensile strain, showing a typical step-and-terrace surface and coherent epitaxy characteristic on the SAO buffer layer. The electrical and magnetic properties of SRO are very sensitive to buffer layer-controlled epitaxial strain. The tensile strained SRO films show quite different electrical transport properties at low temperature, i.e., appearance of metal-insulator transition and positive magnetoresistances and the absence of non-Fermi-liquid behavior. Additionally, magnetic anisotropy is found in both the tensile and the compressively strained SRO, while the strain-relaxed film shows isotropic magnetization. Based on the electrical and magnetic properties, a phase diagram of SRO on the SAO buffer layer has been constructed.