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Density of states (DOS) with different values of external magnetic field (H), for both uncharged and charged conditions at H = 0 (a), H = 0.1H s (b), and H = H s (c). The Fermi level is at 0 eV. The valence band is completely filled for all cases. After charging, the center of the conduction band moves closer to the fermi level. The occupation of the conduction band depends on the magnetic field. At H = H s the conduction band is partially filled. (d) Calculated I-V characteristics of the RS system for different H. At a fixed magnetic field the system changes from a HRS to LRS when the voltage is swept from 0 to 1.5 V. At higher magnetic field the resistance of the system reduces, and it reaches a compliance limit at a smaller applied voltage.
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(a) Cross sectional transmission electron microscope (TEM) image of Co/Al2O3 multilayers. The dark spots are Co islands and the white region is an Al2O3 insulating matrix. The Al2O3 thickness is 4 nm and the nominal thickness of a Co layer is about 0.5 nm. The inset shows a schematic of Co/Al2O3 multilayer system. (b) I-V characteristics of the device during the forming process. The forming voltage is around 12 V. (c) Threshold resistive switching behavior due to charge accumulation in the granules. (d) Experimental I-V characteristics of threshold switching for different external magnetic fields. The inset shows how the switching voltage (V t ) changes with the external magnetic fields.
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We propose a theoretical model of magnetic field dependence of hysteretic switching in magnetic granular system. The model is based on the self-trapped electrons mechanism. Our calculations show that the switching voltage may be significantly decreased with increasing the magnetic field. The underlying mechanism is the influence of the magnetic field on electron occupation of the conduction band, which depends on the materials used in magnetic granular system, concentration of magnetic granules in the insulating matrix, applied voltage, and the charge accumulation on the granules. We support our theoretical calculations by measuring the magnetic field dependence of resistive switching behaviour in Co/Al2O3 granular multilayers. Our experimental results are in qualitative agreement with the proposed theory.
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