Magnetic properties of quasi-two-dimensional La_1−xSr_1+xMnO₄ and the evolution of itinerant electron ferromagnetism in the SrO·(La_1−xSr_xMnO₃)_n system

Abstract

Quasi-two-dimensional oxides of the La_1−xSr_1+xMnO₄ system, possessing the K₂NiF₄ structure, show no evidence for ferromagnetic ordering in contrast to the corresponding three-dimensional La_1−xSr_xMnO₃ perovskites. Instead, there is an increasing tendency toward antiferromagnetic ordering with increasingx in La_1−xSr_1+xMnO₄. Furthermore, these oxides are relatively high-resistivity materials over the entire compositional range. Substitution of Ba for Sr in La_0.5Sr_1.5MnO₄ decreases the ferromagnetic interaction. Increasing the number of perovskite layers in SrO·(La_1−xSr_xMnO₃)_n causes an increase in electrical conductivity as well as ferromagnetic interaction. The oxide becomes a highly conducting ferromagnet when n≥2.