Mott versus Slater-type metal-insulator transition in Mn-substituted Sr3Ru2O7

We present a temperature-dependent x-ray-absorption (XAS) and resonant elastic x-ray scattering (REXS) study of the metal-insulator transition (MIT) in Sr-3(Ru1-xMnx)(2)O-7. The XAS results reveal that the MIT drives the onset of local antiferromagnetic correlations around the Mn impurities, a precursor of the long-range antiferromagnetism detected by REXS at T-order < T-MIT. This establishes that the MIT is of the Mott type (electronic correlations) as opposed to Slater type (magnetic order). While this behavior is induced by Mn impurities, the (1/4, 1/4, 0) order exists for a wide range of Mn concentrations, and points to an inherent instability of Sr3Ru2O7.