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nanoelectronic devices with the effect of resistive switching, which consists in a reversible change of resistance in response to electrical stimulation [5] and is identified with the memristive effect. [6] Despite the significant progress in understanding of the memristive effect and approaching maturity of the technology of resistiveswitching devices over the last 10 years, there are still a number of fundamental problems to solve.A key problem on the way of using resistive-switching devices as programmable elements in memory devices and mixed analog-digital processors of new generation is the variability of resistive switching parameters inherent to memristive thin-film devices. [7] Achieving stable switching between the nonlinear resistive states is also an important task on the way to implementing large passive crossbar arrays of memristors and solving the problem of leakage currents in them. [8,9] Metal-oxide memristive devices are most compatible with the traditional complementary metal oxide semiconductor (CMOS) process and exhibit a valence change memory effect. [10] The variation of switching parameters in such devices is caused by the stochastic nature of migration of oxygen ions and/or vacancies responsible for the local oxidation and recovery of conductive channels (filaments) and is accompanied by the degradation of switching parameters in the case of uncontrolled oxygen exchange between the dielectric and electrode materials.The traditional approaches to control the reproducibility of resistive switching include the formation of special electric field concentrators [11][12][13] and appropriate selection of materials/interfaces in memristive device structure. In the latter case, bilayer or multilayer structures are formed, in which the switching oxide alternates with a barrier/buffer layer (layers) to control the migration of oxygen vacancies, [14,15] with a layer of low dielectric constant [16,17] to obtain nonlinear currentvoltage (I-V) characteristics, or with a layer of higher/lower thermal conductivity [18,19] for the removal/retention of heat in the switching area and to achieve analog switching character. To tune the resistive states with given accuracy, regardless of

The (In,Fe)Sb layers with the Fe content up to 13 at. % have been grown on (001) GaAs substrates using the pulsed laser deposition. The TEM investigations show that the (In,Fe)Sb layers are epitaxial and free of the inclusions of a second phase. The observation of the hysteretic magnetoresistance curves at temperatures up to 300 K reveals that the Curie point is above room temperature. The resonant character of magnetic circular dichroism confirms the intrinsic ferromagnetism in the (In,Fe)Sb layers. We suggest that the ferromagnetism of the (In,Fe)Sb matrix is not carrier-mediated and apparently is determined by the mechanism of superexchange interaction between Fe atoms (This work was presented at the XXI Symposium Nanophysics and Nanoelectronics, Nizhny Novgorod, March, 13-16, 2017 (book of proceedings v.1, p. 195), http://nanosymp.ru/UserFiles/Symp/2017_v1.pdf)

The low-frequency noise in a nanometer-sized virtual memristor consisting of a contact of a conductive atomic force microscope (CAFM) probe to an yttria stabilized zirconia (YSZ) thin film deposited on a conductive substrate is investigated. YSZ is a promising material for the memristor application since it is featured by high oxygen ion mobility, and the oxygen vacancy concentration in YSZ can be controlled by varying the molar fraction of the stabilizing yttrium oxide. Due to the low diameter of the CAFM probe contact to the YSZ film (∼10 nm), we are able to measure the electric current flowing through an individual filament both in the low resistive state (LRS) and in the high resistive state (HRS) of the memristor. Probability density functions (Pdfs) and spectra of the CAFM probe current in both LRS and HRS are measured. The noise in the HRS is found to be featured by nearly the same Pdf and spectrum as the inner noise of the experimental setup. In the LRS, a flicker noise 1/fγ with γ ≈ 1.3 is observed in the low-frequency band (up to 8 kHz), which is attributed to the motion (drift/diffusion) of oxygen ions via oxygen vacancies in the filament. Activation energies of oxygen ion motion determined from the flicker noise spectra are distributed in the range of [0.52; 0.68] eV at 300 K. Knowing these values is of key importance for understanding the mechanisms of the resistive switching in YSZ based memristors as well as for the numerical simulations of memristor devices.

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