Structure-property coupling in Sr₃(Ru_1-xMn _x)₂O₇

Layered ruthenates are prototype materials for the study of structure-property correlations. We report the structural and physical properties of double-layered perovskite Sr₃(Ru_1-xMn _x)₂O₇ single crystals with 0≤x≤0.7. Single-crystal x-ray diffraction refinements reveal that Mn doping on the Ru site leads to the shrinkage of unit-cell volume and the disappearance of (Ru/Mn)O₆ octahedron rotation when x 0.16, but the crystal structure remains tetragonal. Upon doping, the electrical resistivity reveals a metallic character (dρ/dT 0) at high temperatures but insulating behavior (dρ/dT<0) below a characteristic temperature T_MIT. Interestingly, T_MIT is different from T_M, at which magnetic susceptibility reaches maximum. While T_MIT increases monotonically with increasing x,T_M displays a nonmonotonic dependence with x even though the effective spin increases from S∼1 (x=0) to ∼3/2 (x=0.7). The phase diagram consists of three distinct magnetic ground states due to local structure change.