When strong spin-orbit coupling removes orbital degeneracy, it would at the same time appear to render the Jahn-Teller mechanism ineffective. We discuss such a situation, the t2g manifold of iridates, and show that, while the Jahn-Teller effect does indeed not affect the j eff = 1/2 antiferromagnetically ordered ground state, it leads to distinctive signatures in the j eff = 3/2 spinorbit exciton. It allows for a hopping of the spin-orbit exciton between the nearest neighbor sites without producing defects in the j eff = 1/2 antiferromagnet. This arises because the lattice-driven Jahn-Teller mechanism only couples to the orbital degree of freedom, but is not sensitive to the phase of the wave function that defines isospin jz. This contrasts sharply with purely electronic propagation, which conserves isospin, and presence of Jahn-Teller coupling can explain some of the peculiar features of measured resonant inelastic x-ray scattering spectra of Sr2IrO4.
We perform fully relativistic first principles calculations of the exchange interactions and the magnetocrystalline anisotropy energy (MAE) in an Fe/FePt/Fe sandwich system in order to elucidate how the presence of Fe/FePt (soft/hard magnetic) interfaces impacts on the magnetic properties of Fe/FePt/Fe multilayers. Throughout our study we make comparisons between a geometrically unrelaxed system and a geometrically relaxed system. We observe that the Fe layer at the Fe/FePt interface plays a crucial role inasmuch its (isotropic) exchange coupling to the soft (Fe) phase of the system is substantially reduced. Moreover, this interfacial Fe layer has a substantial impact on the MAE of the system. We show that the MAE of the FePt slab, including the contribution from the Fe/FePt interface, is dominated by anisotropic inter-site exchange interactions. Our calculations indicate that the change in the MAE of the FePt slab with respect to the corresponding bulk value is negative, i.e., the presence of Fe/FePt interfaces appears to reduce the perpendicular MAE of the Fe/FePt/Fe system. However, for the relaxed system, this reduction is marginal. It is also shown that the relaxed system exhibits a reduced interfacial exchange. Using a simple linear chain model we demonstrate that the reduced exchange leads to a discontinuity in the magnetisation structure at the interface.
Influence of the structure defects on the magnetic properties of the FePt/Fe bilayer 2 Abstract. Thin magnetic multilayered films containing FePt have attracted a lot of attention recently due to their possible usage in ultra-high density magnetic storage. Although structure defects play a dramatic role in the magnetization process and influence magnetic properties in general this dependence haven't been studied thoroughly. The main aim of this work was to perform theoretical investigation of the magnetic properties of FePt and Fe/FePt thin films with high coercivity with respect to the structure defects such as anisotropy constant, magnetization saturation, exchange constant fluctuations and easy axis deviation. For selected defect patterns the coercive field dependence on layer thicknesses was analysed. Numerical study of the bilayer with hard magnetic layer having the planar anisotropy was carried on using micromagnetic calculations. Values of layers thickness have been found optimal for perspective applications, the dependence of the hysteresis loop shape upon the magnetization process has been shown and analysed.
Currently, a new generation of immunomodulators, cytokines, are widely used in medicine and veterinary medicine. Cytokines are active in very low concentrations, they regulate the proliferation and differentiation of cells of the immune system. Taking into account the high biological activity for cells of animal, plant and microbial origin in vivo and in vitro, we conducted the present studies, the purpose of which was to study the possibility of using cytokines as activators of the metabolism of animal cell cultures in vitro for the reproduction of viruses on them. In the experiments, cell cultures MDBK and BHK-21/13-02 obtained from the collection of cell cultures of the Federal State Budget Scientific Institution FSBSI «FCTRBS-ARRVI» were used. Nutrient media were used for growing cell cultures: Needle MEM, solution of Versen, trypsin, Hanks, bovine blood serum (BRS), fetal blood serum (FBMS). As activators of cell metabolism, commercial cytokines were used: IL-3, IL-6, colon-stimulating factor G-CSF produced by Cytokin LLC (St. Petersburg). Stimulating and inhibitory doses of cytokines were experimentally determined and added to media with cell cultures at the rate of 30 to 500 pg/cm3. It was found that among the tested classes of cytokines, interleukin-6 (IL-6) turned out to be the most active, which, when introduced into the growth medium at a concentration of 30-60 ng/cm3, had a metabolism-stimulating effect, providing a proliferation index of MDBK cells by 1.33 times and cell lines VNK-21/13-02 - 1.17 times, respectively.
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