Effect of spacer layer thickness on magnetic and electrical properties of La0.7Sr0.3MnO3/SrTiO3 superlattices

The effects of spacer layer (SrTiO₃) thickness on the magnetic and electrical properties of La_0.7Sr_0.3MnO₃/SrTiO₃ superlattices has been studied by fabricating a series of multilayers on SrTiO₃ [100] substrates by pulsed laser deposition. High quality of the films was ensured by X-ray diffraction and transmission electron microscopy. All studied films are ferromagnetic below a transition temperature T_C. The T_C as well as saturation magnetization M_S depend on the thickness of SrTiO₃. However, these dependences are nonmonotonic. The electrical resistivity is metallic-like below 300 K. The magnetoresistance measured at 20 K has been found to depend on the SrTiO₃ thickness and correlates with the magnetic measurements. The results are discussed in terms of surface corrugation due to epitaxial strain, surface dead-layer concept, and interlayer coupling.