Electrical transport and magnetic properties of the Ruddlesden-Popper phases Sr3Fe2−xRuxO7 (0≤x≤1.4)

The Ru-doped Ruddlesden-Popper (RP)-type compounds Sr3Fe2−xRuxO7 (x=0, 0.3, 0.6, 1.0 and 1.4) were synthesized and checked by X-ray diffraction (XRD). The doping dependencies of unit cell parameters, resistivity (ρ-T) and magnetization (M-T) were studied. Further, hysteresis (M-H) measurements were done on the sample x=1.0. Resistance measurements indicate that all the samples are insulators and electric transport properties fit the two-dimensional variable range hopping (VRH) model very well. Magnetism measurements show that a spin-glass state exists in all the measured samples when the temperature is lower than about 25 K. The temperature dependencies of the inverse molar magnetic susceptibility indicate that weak ferromagnetism occurs at a much higher temperature than that of glassy transition.