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(a) Schematic of the device, consisting of an organic layer on top of a ferromagnetic thin film. The thickness of the magnetic film, t, is varied by varying n, the number of bilayer repeats. (b) The rms value of the fringe fields 12 nm above the film surface for a 1D periodic domain structure, magnetized up/down with a 500 nm period, as a function of the film thickness. The lower panel shows MFM images of magnetic films with n = 5, 10, 15, and 22. Images are taken at zero field after applying a large in-plane magnetic field to demagnetize the film. Image sizes are 5 × 2.5 μm2. (c) Magnetoconductivity of an organic thin film (Alq3 on top of a n = 22 ferromagnetic layer) and magnetization hysteresis loop with perpendicular applied field for the same device.
Magnetoconductivity of devices with 25 nm of PEDOT and 40 nm of Alq3 on top of ferromagnetic thin films and magnetic hysteresis curves of the same films (applied field perpendicular to the film plane). Different panels correspond to different films with different coercive fields and thicknesses.
Magnetoconductivity of devices with 25 nm of PEDOT and 40 nm of Alq3 on top of magnetic films (applied field in the film plane). Different panels correspond to different films with different thicknesses. Insets show time traces of magnetoconductivity in the same devices for a sequence of in-plane magnetic field from 0 T to 1 T and back to 0 T; shaded areas correspond to zero applied field. In the initial state the ferromagnetic film was magnetized to its saturation value.
Upper panel shows the field sequence to prepare remanent states at zero magnetic field: a large negative magnetic field saturates the ferromagnet, then a small positive field sets a magnetization state in the ferromagnet, and finally the field is reduced to zero and the ferromagnet remains at a remanent magnetization state. Panels (a)–(c) show results of the organic's conductivity for magnetic films of number of repeats n and different fringe-field strengths. Conductivity curves are measured at values from the field sequence marked with stars in the schematic field sequence: positive applied field (blue) and at zero applied field (red).
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