The structure of the (001) surface of Sr$_{3}$(Ru$_{1-x}$Mn$_{x })_{2}$O$_{7}$

It has become quite clear that small structural distortions at the surface of complex materials like the transition-metal-oxides can have profound effects on the physical properties at the surface. We have investigated the surface structure of Sr$_{3}$(Ru$_{1-x}$Mn$_{x })_{2}$O$_{7 }$as a function of Mn substitution for Ru. Analysis of Sr$_{3}$Ru$_{2}$O$_{7}$ indicates an unexpected tilt (4\r{ }) as well as a larger rotation for the top RuO$_{6}$ octahedron (12\r{ }). Preliminary results indicate the tilted structural phase seems to be progressively suppressed by the substitution of Ru for Mn in the doped system. Electron diffraction patterns for a Mn doping level of only 10{\%}, already indicate a very small tilt angle at the surface ($\sim $1\r{ }). The question is what effect this structural change will have on the magnetic ordering in the bilayered manganite. Extensive studies on the single-layered (Sr,Ca)2RuO$_{4}$ system reveal that rotation and tilt of RuO$_{6}$ octahedra plays a critical role in their physical properties, both in bulk and at the surface.