La 1 − x Sr x MnO 3 superlattices composed of ferromagnetic x = 0.4 and antiferromagnetic x = 0.55 layers

A systematic study is presented for structural characterization and physical properties of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3} (x=0.4, 0.55)$ single-layer films and superlattices composed of alternating stacks of these layers. By increasing the doping level from $x=0.4$ to $x=0.55,$ the ground state of single-layer films is drastically changed from ferromagnetic to layered type antiferromagnetic with orbital ordering. The constituent layers in the superlattices appear to keep their ground states. Therefore the carriers are confined in the constituent layers, resulting in the modulation not only in spin but also in orbital 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., $l~1.2 \mathrm{nm}),$ indicating restoration of the electronic coupling between the neighboring $x=0.4$ layers, which are otherwise decoupled by the $x=0.55$ layers.