Crystal structure and magnetic order in bilayered La1.39Sr1.61Mn2O7

Neutron diffraction, ac magnetic susceptibility, and dc electric resistivity measurements were performed to study the structural, electric, and magnetic properties of naturally bilayered La1.39Sr1.61Mn2O7. Although the system was believed to be under-doped, an insulator-to-metal transition was clearly seen at around 110 K. An anomaly was also evident in the magnetic susceptibility, signifying the ordering of the Mn spins. The Mn spins were found to order three-dimensionally below 90 K. Both ferromagnetic and antiferromagnetic correlations were present. Ferromagnetic couplings were observed within each bilayer, whereas a non-collinear arrangement between the adjacent bilayers or a magnetic phase separation behavior was found. No significant canting of spins between the neighboring layers within each bilayer was found.