  Stoichiometric Sr2IrO4 is a ferromagnetic Jeff = 1/2 Mott insulator driven by
strong spin-orbit coupling. Introduction of very dilute oxygen vacancies into
single-crystal Sr2IrO4-delta with delta < 0.04 leads to significant changes in
lattice parameters and an insulator-to-metal transition at TMI = 105 K. The
highly anisotropic electrical resistivity of the low-temperature metallic state
for delta ~ 0.04 exhibits anomalous properties characterized by non-Ohmic
behavior and an abrupt current-induced transition in the resistivity at T* = 52
K, which separates two regimes of resisitive switching in the nonlinear I-V
characteristics. The novel behavior illustrates an exotic ground state and
constitutes a new paradigm for devices structures in which electrical
resistivity is manipulated via low-level current densities ~ 10 mA/cm2
(compared to higher spin-torque currents ~ 107-108 A/cm2) or magnetic
inductions ~ 0.1-1.0 T.
