Magnetoresistance of heteroepitaxial La0.7Sr0.3MnO3/SrTiO3 multilayers

Perovskite multilayers built by thin layers of the half-metal La 0.7 Sr 0.3 MnO 3 (LSMO) and the insulator SrTiO 3 have been epitaxially grown by pulsed laser deposition. High quality superlattices have been obtained as indicated by the results of X-ray diffraction and transmission electron microscopy. Magnetization and in-plane electrical transport of multilayers with a manganite thickness of 10 nm > d LSMO > 1.9 nm have been studied. A systematic suppression of ferromagnetic order and metallic conductivity with decreasing d LSMO has been observed. The properties of the ultrathin manganite layers can be well understood assuming a phase separation into ferromagnetic metallic and insulating regions, as it has been established for other manganites recently. Within this regime, large magnetoresistance (MR) in a wide range of temperatures as well as anomalous MR effects, including positive MR and very large negative MR in dependence on d LSMO , have been observed.