La1-xSrxMnO3 superlattices composed of ferromagnetic x=0.4 and antiferromagnetic x=0.55 layers

A systematic study is presented for structural characterization and physica l properties of La1-xSrxMnO3 (x=0.4, 0.55) single-layer films and superlatt ices composed of alternating stacks of these layers. By increasing the dopi ng level from x=0.4 to x=0.55, the ground state of single-layer films is dr astically changed from ferromagnetic to layered type antiferromagnetic with orbital ordering. The constituent layers in the superlattices appear to ke ep their ground states. Therefore the carriers are confined in the constitu ent layers, resulting in the modulation not only in spin but also in orbita l structures along the stacking direction. Magnetoresistance is pronounced in the superlattices at low temperatures when the x=0.55 layer is very thin (e.g., approximate to 1.2 nm), indicating restoration of the electronic co upling between the neighboring x=0.4 layers, which are otherwise decoupled by the x=0.55 layers.