Electrically-driven phase transition in magnetite nanostructures

Magnetite (Fe$_{3}$O$_{4}$), an archetypal transition metal oxide, has been used for thousands of years, from lodestones in primitive compasses[1] to a candidate material for magnetoelectronic devices.[2] In 1939 Verwey[3] found that bulk magnetite undergoes a transition at T$_{V}$ $\approx$ 120 K from a high temperature "bad metal" conducting phase to a low-temperature insulating phase. He suggested[4] that high temperature conduction is via the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering upon cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial.[5-11] Here we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.Comment: 17 pages, 4 figure

Coexistence of ferromagnetism and high-temperature superconductivity in Dy-doped BiPbSrCaCuO

Ferromagnetism was found to coexist with superconductivity in Dy-doped BiPbSrCaCuO-2212 single crystals up to the superconducting critical temperature T-c similar to 80 X. Several experimental tests indicated that the phenomenon is intrinsic to the entire specimen rather than due to separate phases or to isolated impurities.X114sciescopu

Selective synthesis of alpha-Fe2O3 thin films and effect of the deposition temperature and lattice oxygen on the catalytic combustion of propene

Mountapmbeme Kouotou P, Tian Z-Y, Vieker H, Beyer A, Gölzhäuser A, Kohse-Höinghaus K. Selective synthesis of alpha-Fe2O3 thin films and effect of the deposition temperature and lattice oxygen on the catalytic combustion of propene. JOURNAL OF MATERIALS CHEMISTRY A. 2013;1(35):10495-10504