Perpendicular magnetic anisotropy in La1-xSrxCoO2.5+δ/La2/3Sr1/3MnO3/La1-xSrxCoO2.5+δ trilayers (x=0.05-0.5)

Perpendicular magnetic anisotropy (PMA) of magnetic materials has received much attention because of its potential application to spintronics devices. In general, the tensely strained (001)-La2/3Sr1/3MnO3 (LSMO) layer is easy plane. Here we demonstrate that the tensile LSMO layer will exhibit an out-of-plane magnetic anisotropy if it is sandwiched between two La1-xSrxCoO2.5+delta (LSCO) layers. The most remarkable observation is that the PMA enhances with the increase of the Sr content in LSCO. It is similar to 2.7 x 10(6) erg/cm(3) for x = 0.05 and similar to 4.3 x 10(6) erg/cm(3) for x = 0.5. This value is two orders of magnitude greater than that obtained by compressively straining the LSMO film (similar to 10(4) erg/cm(3)). Analysis of high resolution lattice image shows the formation of perovskite/brownmillerite-type interfaces in the multilayers: Brownmillerite-like lattice structure forms in the interfacial layers of LSCO, resulting in a coherent tilting of adjacent MnO6 octahedra. This in turn leads to, as evidenced by the analysis of x-ray linear dichroism, selective orbital occupation thus spin reorientation. There is evidence that the brownmillerite-structured LSCO is more easily formed when x is high, which explains the growth of anisotropy constant with the increase of Sr content.