* These authors contributed equally to this work.The future prosperity of information technology strongly depends on creating new device concepts with improved functionality and on successfully scaling of their characteristic lengths.[1] The spectrum of attractive novel non-volatile memory technologies currently being explored to sustain the increase of functionality in semiconductor devices ranges from magnetic random-access-memory [2,3] and chalcogenide phase-change memory [4,5] to resistance-change memory based on transition-metal-oxides. [6][7][8] The latter compounds can be conditioned such that they exhibit a bistable resistance state. The microscopic origin of the resistance-change memory in these transition-metal oxides is not understood. Here we investigate the relevance of oxygen vacancies for the resistance-change memory using the transitionmetal oxide chromium-doped strontium titanate (Cr-doped SrTiO 3 ) as example.Laterally resolved micro-x-ray absorption spectroscopy and infrared thermal microscopy demonstrate that the conditioning process creates an electrically conducting path with a high density of oxygen vacancies which are localized at a Cr ion. Both

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The first direct observation of charge order of Ni(3+delta(')) and Ni(3-delta) by resonant x-ray scattering experiments in an epitaxial film of NdNiO3 is reported. A quantitative value of delta+delta(') = (0.45 +/- 0.04)e was obtained. The temperature dependence of the charge order deviates significantly from those of the magnetic moment and crystallographic structure. This might be an indication of a difference in their fluctuation time scales. These observations are discussed in terms of the temperature-driven metal-insulator transition in the RNiO3 family.

Soft x-ray resonant scattering at the Ni L 2,3 edges is used to test models of magnetic-and orbital-ordering below the metal-insulator transition in NdNiO 3 . The large branching ratio of the L 3 to L 2 intensities of the (1/2 0 1/2) reflection and the observed azimuthal angle and polarization dependence originates form a non-collinear magnetic structure. The absence of an orbital signal and the non-collinear magnetic structure show that the nickelates are materials for which orbital ordering is absent at the metal-insulator transition.

Combining scanning electron microscopy (SEM) and electron-beam-induced current (EBIC) imaging with transport measurements, it is shown that the current flowing across a two-terminal oxide-based capacitor-like structure is preferentially confined in areas localized at defects. As the thin-film device switches between two different resistance states, the distribution and intensity of the current paths, appearing as bright spots, change. This implies that switching and memory effects are mainly determined by the conducting properties along such paths. A model based on the storage and release of charge carriers within the insulator seems adequate to explain the observed memory effect. 61.16.Bg, 72.20.Jv, 73.40.Rw