Surface Magnetic Phase Diagram of Tetragonal Manganites

抄録

To gain insights into the fundamental and characteristic features of the surface of doped manganites, we constructed a general magnetic phase diagram of La_1-xSr_xMnO₃ (001) surfaces in the plane spanned by x and the bulk tetragonal distortion c/a, from the first-principles calculations. We found that the surfaces are quite different from the bulk in the sense that both the (La,Sr)O and MnO₂ terminated surfaces show strong tendency toward antiferromagnetism (A-type and C-type respectively). The basic physics governing the phase diagram can be understood in terms of surface effective doping and surface orbital polarization. It is also found that the strong surface segregation of Sr atoms is mostly caused by the electrostatic interaction and will further enhance the tendency toward surface antiferromagnetism.