RESUMEN
Magnetic domains and magnetization reversal in 40 nm thick films of Fe0.6Al0.4, have been studied by longitudinal magneto-optical Kerr effect. By varying the Ne(+) ion-energy E between 2 and 30 keV (keeping a constant fluence), we varied the depth-penetration of the ions, and thereby influenced the homogeneity of the induced saturation magnetization M(s). The dependence of coercivity on ion energy shows maximum for 5 keV Ne(+). Considerable differences in the magnetic domain formation and magnetization reversal processes were observed: at low E (≤ 5keV), the reversal process is dominated by domain nucleation mechanism (high density of domain nucleation sites), consistent with the occurrence of an inhomogeneous M(s). Films irradiated with E > 5keV ions exhibit significantly low domain nucleation density, and the reversal is dominated by domain propagation mechanism, suggesting homogeneity in induced M(s). These results demonstrate the tunability of magnetization reversal behavior in materials possessing disorder induced magnetic phase transitions.
RESUMEN
Polyphenols of plant origin with wide range of antiradical activity can prevent diseases caused by oxidative and inflammatory processes. In this study, we show using ESR method that the purified water-soluble extract from leaves of Rhus typhina L. containing hydrolysable tannins and its main component, 3,6-bis-O-di-O-galloyl-1,2,4-tri-O-galloyl-ß-D-glucose (C55H40O34), displayed a strong antiradical activity against the synthetic 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) in homogenous (solution) and heterogeneous systems (suspension of DPPH containing liposomes) in the range of 1-10 µg/ml. The C55H40O34 and extract at 1-30 µg/ml also efficiently, but to a various degree, decreased reactive oxygen and nitrogen species (RONS) formation induced in erythrocytes by oxidants, following the sequence: tert-butyl hydroperoxide (tBuOOH) > peroxynitrite (ONOO-) >hypochlorous acid (HClO). The explanation of these differences should be seen in the specificity of scavenging different RONS types. These relationships can be represented for C55H40O34 and the extract by the following order of selectivity: O.-2 ≥ NO· > ·OH > 1O2. The extract exerted a more pronounced antiradical effect in reaction with DPPH and ROS in all models of oxidative stress in erythrocytes in comparison with C55H40O34. The redox processes between the extract components and their specificity in relation to RONS can underlie this effect.