Monte Carlo study of magnetic nanoparticles adsorbed on halloysite Al2Si2O5(OH)4Al_2Si_2O_5(OH)_4 nanotubes

We study properties of magnetic nanoparticles adsorbed on the halloysite surface. For that a distinct magnetic Hamiltonian with random distribution of spins on a cylindrical surface was solved by using a nonequilibrium Monte Carlo method. The parameters for our simulations: anisotropy constant, nanoparticle size distribution, saturated magnetization and geometrical parameters of the halloysite template were taken from recent experiments. We calculate the hysteresis loops and temperature dependence of the zero field cooling (ZFC) susceptibility, which maximum determines the blocking temperature. It is shown that the dipole-dipole interaction between nanoparticles moderately increases the blocking temperature and weakly increases the coercive force. The obtained hysteresis loops (e.g., the value of the coercive force) for Ni nanoparticles are in reasonable agreement with the experimental data. We also discuss the sensitivity of the hysteresis loops and ZFC susceptibilities to the change of anisotropy and dipole-dipole interaction, as well as the 3d-shell occupation of the metallic nanoparticles; in particular we predict larger coercive force for Fe, than for Ni nanoparticles.Comment: 10 pages, 12 figure

Double Counting in LDA+DMFT - The Example of NiO

An intrinsic issue of the LDA+DMFT approach is the so called double counting of interaction terms. How to choose the double-counting potential in a manner that is both physically sound and consistent is unknown. We have conducted an extensive study of the charge transfer system NiO in the LDA+DMFT framework using quantum Monte Carlo and exact diagonalization as impurity solvers. By explicitly treating the double-counting correction as an adjustable parameter we systematically investigated the effects of different choices for the double counting on the spectral function. Different methods for fixing the double counting can drive the result from Mott insulating to almost metallic. We propose a reasonable scheme for the determination of double-counting corrections for insulating systems.Comment: 7 pages, 6 figure

Аcute renal failure in patients with implanted LVAD in the early postoperative period

AKI is one of the major complications in the cardiac surgery group of patients in the world. In patients with LVAD in the short postoperative period, the situation with such a complication as AKI is associated with the state of hemodynamics and fluctuations in the parameters of the hemostasis system. The purpose of this scientific work is to analyze the state of the blood coagulation system and its response to therapy and complications in the early postoperative period in fifty patients with implanted devices for mechanical support of the left ventricle, left ventricle assist device, LVAD, in the Silesian Heart Disease, Poland. Patients were divided into two groups, a control group receiving classical anticoagulation targeted therapy (ATT), which included the most controlled monotherapy with heparin, after reaching the target values of APTT, the addition and transition to monotherapy with warfarin until reaching the target INR and ASA, and the main, research group, who received an alternative ATT consisting of the previous one with the addition of P2Y12-receptor blockers and Xa-factors. The results showed that the control group of patients with classical anticoagulant targeted therapy had greater mortality associated with AKI than the patients of the study group, and it was also demonstrated that the initially longer duration of surgery and intraoperative polyuria gave a greater percentage of AKI in the postoperative period. The work was carried out within the framework of a bilateral agreement on scientific cooperation between the Department of Anesthesiology & Intensive Care at the National Medical Academy of Post-Graduate Education Named After P.L. Shupyk and the Silesian Center for Heart Diseases (Poland). This article is part of the analysis of the work on the analysis of the blood coagulation system in patients after implantation of the left ventricular mechanical circulatory support system with the analysis of such postoperative complication as acute kidney failure

Spatial inversion of gyrotropy parameter in conductivity tensor and charge transport peculiarities

Charge transfer is discussed for the case when gyrotropy parameter (Hall coefficient) varies along transport л-direction and inverses its sign. This situation takes place in contacts of the serially joined materials having electron and hole types of conductivity. Spatial inhomogeneity of conductivity and inversion of Hall coefficient sign are analyzed in terms of electric potential and current density distribution. It is shown that under inhomogeneous magnetic field the steady current skinning takes place in plate sample

Correlated band theory of spin and orbital contributions to Dzyaloshinskii-Moriya interactions

A new approach for calculations of Dzyaloshinskii-Moriya interactions in molecules and crystals is proposed. It is based on the exact perturbation expansion of total energy of weak ferromagnets in the canting angle with the only assumption of local Hubbard-type interactions. This scheme leads to a simple and transparent analytical expression for Dzyaloshinskii-Moriya vector with a natural separation into spin and orbital contributions. The main problem was transferred to calculations of effective tight-binding parameters in the properly chosen basis including spin-orbit coupling. Test calculations for La$_2$CuO$_4$ give the value of canting angle in a good agreement with experimental data.Comment: 4 pages, 1 figur

Magnetostimulated inhomogeneity of electric field in aluminum

The results of low temperature experimental and theoretical study of potential distribution of stationary electric field in Al under the action of inhomogeneous magnetic field are presented

Hybridization and spin-orbit coupling effects in quasi-one-dimensional spin-1/2 magnet Ba3Cu3Sc4O12

We study electronic and magnetic properties of the quasi-one-dimensional spin-1/2 magnet Ba3Cu3Sc4O12 with a distinct orthogonal connectivity of CuO4 plaquettes. An effective low-energy model taking into account spin-orbit coupling was constructed by means of first-principles calculations. On this basis a complete microscopic magnetic model of Ba3Cu3Sc4O12, including symmetric and antisymmetric anisotropic exchange interactions, is derived. The anisotropic exchanges are obtained from a distinct first-principles numerical scheme combining, on one hand, the local density approximation taking into account spin-orbit coupling, and, on the other hand, projection procedure along with the microscopic theory by Toru Moriya. The resulting tensors of the symmetric anisotropy favor collinear magnetic order along the structural chains with the leading ferromagnetic coupling J1 = -9.88 meV. The interchain interactions J8 = 0.21 meV and J5 = 0.093 meV are antiferromagnetic. Quantum Monte Carlo simulations demonstrated that the proposed model reproduces the experimental Neel temperature, magnetization and magnetic susceptibility data. The modeling of neutron diffraction data reveals an important role of the covalent Cu-O bonding in Ba3Cu3Sc4O12.Comment: 11 pages, 12 figure

Supervised learning magnetic skyrmion phases

We propose and apply simple machine learning approaches for recognition and classification of complex non-collinear magnetic structures in two-dimensional materials. The first approach is based on the implementation of the single-hidden-layer neural network that only relies on the z projections of the spins. In this setup one needs a limited set of magnetic configurations to distinguish ferromag- netic, skyrmion and spin spiral phases, as well as their different combinations in transitional areas of the phase diagram. The network trained on the configurations for square-lattice Heisenberg model with Dzyaloshinskii-Moriya interaction can classify the magnetic structures obtained from Monte Carlo calculations for triangular lattice and vice versa. The second approach we apply, a minimum distance method performs a fast and cheap classification in cases when a particular configuration is to be assigned to only one magnetic phase. The methods we propose are also easy to use for analysis of the numerous experimental data collected with spin-polarized scanning tunneling microscopy and Lorentz transmission electron microscopy experiments.Comment: 9 pages, 14 figures. Accepted for publication in Physical Review

First-principles modelling of magnetic excitations in Mn12

We have developed a fully microscopic theory of magnetic properties of the prototype molecular magnet Mn12. First, the intra-molecular magnetic properties have been studied by means of first-principles density functional-based methods, with local correlation effects being taken into account within the local density approximation plus U (LDA+U) approach. Using the magnetic force theorem, we have calculated the interatomic isotropic and anisotropic exchange interactions and full tensors of single-ion anisotropy for each Mn ion. Dzyaloshinskii-Moriya (DM) interaction parameters turned out to be unusually large, reflecting a low symmetry of magnetic pairs in molecules, in comparison with bulk crystals. Based on these results we predict a distortion of ferrimagnetic ordering due to DM interactions. Further, we use an exact diagonalization approach allowing to work with as large Hilbert space dimension as 10^8 without any particular symmetry (the case of the constructed magnetic model). Based on the computational results for the excitation spectrum, we propose a distinct interpretation of the experimental inelastic neutron scattering spectra.Comment: 8 pages, 2 figures. To appear in Physical Review

Effect of pre-seed and foliar treatment with nano-particle solutions on seedling development of tiger nut (Cyperus Esculentus L.) plants

Received: December 28th, 2020 ; Accepted: March 28th, 2021 ; Published: April 5th, 2021 ; Correspondence: [email protected] are part of enzymes and play an important role in plant germination. Purpose of our study was to establish the effect of pre-seed treatment of chufa tubers with metal nanoparticles on the growth of the root system and seedlings in the early stages of development. Laboratory tests were performed on seed of tiger nut cultivar Pharaoh. Experiment involved two methods of treatment: pre-sowing treatment of seeds with nano-particles solutions of manganese, zinc, copper and iron with a concentration of 60 ppm and re-application of these solutions after seedling emergence. The weight of seedlings and roots was determined at 3rd and 10th days after emergence in treated and untreated variants. Pre-sowing treatment of chufa tubers with all forms of micronutrients significantly increased the weight of the plant (excluding the weight of seeds), and the most effective were treatments with copper and iron. Treatment with copper colloidal solution increases in root weight at 3rd day on 156% compared to control without treatment and this dynamic stayed at 10th day. Most affective treatment is iron colloidal solution. This treatment gives +99% of root weight at 3rd day and 194% at 10th day after germination compared to control in same time. Colloidal forms of manganese, copper and iron also significantly increased the weight of the shoot. Increase in the mass of roots, shoots and plants is observed in plants with foliar fertilizing, but a few variants have an insignificant difference or inhibit the assimilation processes of plants. Pre-sowing treatment with zinc citrate at 60 ppm decreased root and shoot weight in chufa