Magnetic properties of quasi-two-dimensional La1−xSr1+xMnO4 and the evolution of itinerant electron ferromagnetism in the SrO · (La1−xSrxMnO3)n system

Quasi-two-dimensional oxides of the La1−x Sr1+x MnO4 system, possessing the K2NiF4 structure, show no evidence for ferromagnetic ordering in contrast to the corresponding three-dimensional La1−x Sr x MnO3 perovskites. Instead, there is an increasing tendency toward antiferromagnetic ordering with increasingx in La1−x Sr1+x MnO4. Furthermore, these oxides are relatively high-resistivity materials over the entire compositional range. Substitution of Ba for Sr in La0.5Sr1.5MnO4 decreases the ferromagnetic interaction. Increasing the number of perovskite layers in SrO · (La1−x Sr x MnO3) n causes an increase in electrical conductivity as well as ferromagnetic interaction. The oxide becomes a highly conducting ferromagnet whenn ≥ 2.