Aleksander L. Danilyuk

Graphene-based hybrid magnetic systems are promising platforms for spintronic applications, yet the mechanisms governing magnetic correlations in these two-dimensional (2D) architectures remain incompletely understood. Here, we investigate the magnetic behavior of Co/CoO core–shell nanoparticles electrochemically deposited on graphene, focusing on the 25–50 K range, where the coercivity and exchange bias field reach their maximum values. Using a modified 2D integral-law framework for approaching magnetic saturation, adapted for 2D systems via the Meyer integral transform, we reconstruct the real-space correlation functions (CFs) of the magnetic anisotropy axes and extract the main micromagnetic parameters. The analysis reveals three distinct types of CFs, monotonic, non-monotonic, and jump-like, which we tentatively associate with different microstructural configurations, including isolated nanoparticles, dense clusters, and sparse conglomerates separated by graphene domain boundaries. The monotonic CFs exhibit long-range coherence of the magnetic anisotropy axes extending over nearly one micrometer. We propose that this long-range behavior may arise from a dual-scale mechanism: indirect RKKY-type exchange through the graphene layer, combined with strong local anisotropy from the CoO shells, which pins the magnetization of individual Co cores via exchange bias. These interpretations are presented as plausible hypotheses, and further experimental verification is required.

This study investigates the effect of temperature on the performance of the single-walled carbon nanotube (SWCNT) film/Si photodetector. Specifically, the photocurrent across a SWCNT/Si heterojunction when illuminated with light of 632.8 nm wavelength of different powers was studied in detail in a wide temperature range, from 20 to 300 K. The objective was to determine the parameters of the heterojunction, which is inherently inhomogeneous, and to identify the main ones that determine the optoelectronic figures of merit of a photodetector based on it. The barrier height and its temperature dependence were determined within the framework of the theory of thermionic emission, taking into account the non-uniform distribution of the barrier height over the heterojunction area. The parameters of the heterojunction and SWCNT/Si interface and their temperature dependences were calculated based on the known temperature dependences of the concentration of charge carriers and ionized impurities in Si using the Poisson equation based on Fermi–Dirac statistics. The obtained results indicate the importance of interplay between the effects of reducing the barrier height and the processes of decreasing the separation efficiency of nonequilibrium charge carriers and increasing the rate of their recombination.

The charge properties and regularities of mutual influence of the electro-physical parameters in a metal (M)/insulator (I)/two-dimensional crystal heterostructure were studied. In one case, the transition metal dichalcogenide (TMD) MoS₂ was considered as a two-dimensional crystal, and in another the Weyl semi-metal (WSM) ZrTe₅, representative of a quasi-two-dimensional crystal was chosen for this purpose. By self-consistently solving the electrostatic equations of the heterostructures under consideration and the Fermi–Dirac distribution, the relationship between such parameters as the concentration of charge carriers, chemical potential, and quantum capacitance of the TMD (WSM), as well as the capacitance of the I layer and the interface capacitance I–TMD (WSM), and their dependence on the field electrode potential, have been derived. The conditions for the emergence of charge instability and the critical phenomena caused by it are also determined.