Universal, giant and nonvolatile resistive switching is demonstrated for oxide tunnel junctions with ferroelectric PbZr0.2 Ti0.8 O3 , ferroelectric BaTiO3, and paraelectric SrTiO3 tunnel barriers. The effects are caused by reversible migration of oxygen vacancies between the tunnel barrier and bottom La2/3 Sr1/3 MnO3 electrode. The switching process, which is driven by large electric fields, is efficient down to a temperature of 5 K.

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Electron-transport properties in nanostructures can be modeled, for example, by using the semiclassical Wigner formalism or the quantum-mechanical Green's function formalism. We compare the performance and the results of these methods in the case of magnetic resonant-tunneling diodes. We have implemented the two methods within the self-consistent spin-density-functional theory. Our numerical implementation of the Wigner formalism is based on the finite-difference scheme whereas for the Green's function formalism the finiteelement method is used. As a specific application, we consider the device studied by Slobodskyy et al. ͓Phys. Rev. Lett. 90, 246601 ͑2003͔͒ and analyze their experimental results. The Wigner and Green's function formalisms give similar electron densities and potentials but, surprisingly, the former method requires much more computer resources in order to obtain numerically accurate results for currents. Both of the formalisms can be used to model magnetic resonant tunneling diode structures.

PDF/A is an ISO-standardized version of the Portable Document Format (PDF) specialized for the digital preservation of electronic documents. The extension in the file name is pdf. PDF/A differs from "normal" PDF in that features ill-suited for long-term archiving are omitted. PDF/A embeds all fonts used in the document within the PDF file, so that the user of your file will not have to have the same fonts that you used to create the file installed on their computer in order to read it. Recommended versions are PDF/A-1a, -1b, -2a or -2b.PDF/A conversion -how to convert files to the PDF/A -format using different tools Microsoft Word (Office) and PDF-Xchange pro/Editor are installed on all Windows workstations managed by Aalto IT.