Anomalous magnetic and transport behavior in the magnetic insulator Sr3Ir2O7 -: art. no. 214412

We report magnetic and transport properties of single-crystal Sr3Ir2O7, a bilayered orthorhombic system with Bbca symmetry. Our study reveals that Sr3Ir2O7 is a ferromagnetic insulator with a Curie temperature of T-C = 285 K and a small ordered magnetic moment. The saturation moment mu(S) is found to be less than 0.04mu(B)/Ir or 4% of the expected moment for a localized spin S = 1/2. For fields larger than 1 T the magnetic susceptibility is the superposition of a Curie law (with negligible Weiss temperature) and a constant term. Surprisingly, at low temperatures (<20 K) the magnetization is opposite to the applied magnetic field when Sr3Ir2O7 is cooled in a modest magnetic field (<= 0.2 T). The resistivity rho(T) measured from 1.7 to 1000 K along two principal crystallographic directions exhibits insulating behavior with anomalies corresponding to the magnetic properties. Both the magnetization and the resistivity are strongly anisotropic as a consequence of the layered structure. Possible crystalline field and band scenarios are briefly discussed.