Manganese-induced magnetic symmetry breaking and its correlation with the metal-insulator transition in bilayered S r 3 ( R u 1 − x M n x ) 2 O 7

Bilayered Sr3Ru2O7 is an unusual metamagnetic metal with inherently antiferromagnetic (AFM) and ferromagnetic (FM) fluctuations. Partial substitution of Ru by Mn results in the establishment of a metal-insulator transition (MIT) at TMIT and AFM ordering at TM in Sr3(Ru1-xMnx)2O7. Using elastic neutron scattering, we investigated the effect of Mn doping on the magnetic structure, in-plane magnetic correlation lengths and their correlation to the MIT in Sr3(Ru1-xMnx)2O7 (x=0.06 and 0.12). With the increase of Mn doping (x) from 0.06 to 0.12 or the decrease of temperatures for x=0.12, an evolution from an in-plane short-range to long-range antiferromagnetic (AFM) ground state occurs. For both compounds, the magnetic ordering has a double-stripe configuration, and the onset of magnetic correlation with an anisotropic behavior coincides with the sharp rise in electrical resistivity and specific heat. Since it does not induce a measurable lattice distortion, the double-stripe antiferromagnetic order with anisotropic spin texture breaks symmetry from a C4v crystal lattice to a C2v magnetic sublattice. These observations shed light on an age-old question regarding the Slater versus Mott-type MIT.