Structural Stabilization of Antiferromagnetism at the Surface of a Layered Manganite

Here, we present evidence to support the idea that the distinct surface electronic and magnetic state seen in the double-layered manganites (La$_{2}-_{2x}$Sr$_{1+2x}$Mn$_{2}$O$_{7}$, with dopings of 0.3 $< \quad x \quad <$ 0.4) is driven solely by a subtle change in the lattice at the surface, which is consistent with the strong coupling between the lattice, charge, and spin degrees of freedom in these doped transition-metal oxides. A combined experimental and theoretical approach was essential in understanding the origin of the nonmagnetic surface phase. The new measurements and calculations give an insightful explanation of the previous x-ray and tunneling data, which indicated a nonmagnetic and insulating surface bilayer.