Epitaxial strain effect in tetragonal SrRuO_3 thin films

摘要

We report on our characterization of the structural, electrical, and magnetic properties of tetragonal SrRuO_3 (SRO) thin films stabilized under both compressive and tensile strain. These tetragonal films consisting of the deformed RuO_6 octahedra without rotations were coherently grown on (110)_(ortho) NdGaO_3 and (110)_(ortho) GdScO_3 substrates, which provide compressive (-1.7%) and tensile (+1.0%) strains, respectively. The ferromagnetic transition temperature T_C for the compressively strained film is found to be as high as 155 K, while T_C of the film under tensile strain is only 100 K. The longitudinal resistivity ρ_(xx) of the compressively strained films is lower than that of the films under the tensile strain. This is attributed to the enhanced mobility for the compressive-strain case. The magnetic anisotropy also exhibits strong dependence on the substrate-induced epitaxial strain. The film under the compressive strain has the uniaxial magnetic easy axis along the out-of-plane direction, while the easy axis of the film under the tensile strain lies along the in-plane direction parallel to the [1-10]_(GSO) one. The results demonstrate that the electrical and magnetic properties of the tetragonal SRO thin films are closely related to the RuO_6 octahedral deformations due to the substrate-induced strain.