FMR Study of the Porous Silicate Glasses with Fe 3

The results of research on new magnetic materials for biomedical applications are discussed. These materials are porous silicate glasses with magnetic fillers. To ensure the smallest number of components for subsequent removal from the body, the magnetic fillers are bare magnetite nanoparticles (Fe3O4). The magnetic properties of these materials have been investigated using the ferromagnetic resonance method (FMR). The FMR analysis has been complemented by scanning electron microscope (SEM) measurements. In order to examine the effect of time degradation on filling the porous glass with bare magnetite nanoparticles the FMR measurement was repeated five months later. For the samples with high degree of pore filling, in contrast to the samples with low degree of pore filling, the FMR signal was still strong. The influence of different pH values of magnetite nanoparticles aqueous suspension on the degree of filling the pores of glasses is also discussed. The experimental results are supported by computer simulations of FMR experiment for a cluster of N magnetic nanoparticles locked in a porous medium based on a stochastic version of the Landau-Lifshitz equation for nanoparticle magnetization

Photoproduction of Long-Lived Holes and Electronic Processes in Intrinsic Electric Fields Seen through Photoinduced Absorption and Dichroism in Ca_3Ga_{2-x}Mn_xGe_3O_{12} Garnets

Long-lived photoinduced absorption and dichroism in the Ca_3Ga_{2-x}Mn_xGe_3O_{12} garnets with x < 0.06 were examined versus temperature and pumping intensity. Unusual features of the kinetics of photoinduced phenomena are indicative of the underlying electronic processes. The comparison with the case of Ca_3Mn_2Ge_3O_{12}, explored earlier by the authors, permits one to finally establish the main common mechanisms of photoinduced absorption and dichroism caused by random electric fields of photoproduced charges (hole polarons). The rate of their diffusion and relaxation through recombination is strongly influenced by the same fields, whose large statistical straggling is responsible for a broad continuous set of relaxation components (observed in the relaxation time range from 1 to about 1000 min). For Ca_3Ga_{2-x}Mn_xGe_3O_{12}, the time and temperature dependences of photoinduced absorption and dichroism bear a strong imprint of structure imperfection increasing with x.Comment: 20 pages, 10 figure

The Study of Annealed Epitaxial Ferrite-Garnet Thin Films by Means of Ferromagnetic Resonance

The variations of FMR spectra, domain structure and basic magnetic parameters the thin epitaxial ferrite-garnet films of (Y,Sm,Lu,Ca)3(Fe,Ge)5O12 composition resulted from air high-temperature annealing are investigated. On the basis of experimental data analysis was shown that the annealing at Ta = 1100°C, ta>8 hrs and Ta=1150°C, 1200°C, ta=2-10hrs leads to creation of the magnetic transitional layer at the film-substrate boundary. The basic magnetic parameters of films and transitional layers are determined from the FMR spectra. The nature and the formation mechanism of the magnetic transitional layer are discussed

EPR spectroscopy of irradiated bioactive glasses

The X-band (v = 9.4 GHz) EPR spectra of the UV-, X-, and y-irradiated biologically active glass (Bioglass) samples of two different compositions have been investigated at 7 7 and 300 K. The generation efficiency of the electron and hole centers depends strongly on the basic Bioglass composition and is almost independent of ionizing radiation type and presence of the non-controlled Fe3+ impurity in the glass structure. Influence of pre-treatment in NaCI solution and simulated body fluid on formation processes of the radiation-in -duced paramagnetic defects in Bioglass have been investigated. Spin Hamiltonian parame -ters and thermal stability of the radiation-induced centers have been evaluated. Electron structure, formation peculiarities and possibleИсследованы ЭПР-спектры в X-диапазоне (v = 9.4 ГГц) при температурах 77 и 300 K биологически активных (биологических) стекол двух разных составов, облученных УФ, рентгеновскими и у-лучами. Эффективность генерации центров электронного и дырочного типа существенно зависит от основного состава биологического стекла и почти не зависит от вида ионизирующей радиации и присутствия неконтролируемой примеси Fe3+ в структуре стекла. Исследовано также влияние предварительной обработки в растворах NaCI и модельной физиологической жидкости на процессы формирования радиационных парамагнитных дефектов в биологически активных стеклах. Определены параметры спин-гамильтониана и термическая стабильность радиационных центров. Обсуждаются электронная структура, особенности формирования и возможные модели радиационных парамагнитных центров в структуре биологического стекла.Досліджєно ЕПР-спектри в Х-діапазоні (v = 9.4 ГГц) при температурах 77 i 300 K біологічно-активних (біологічних) стекол двох різних складів, опромінених УФ, рентгенівськими і у-променями. Ефективність генерації центрів електронного і діркового типу суттєво залежить від основного складу біологічного скла і майже не залежить від виду іонізуючої радіації та присутності неконтрольованої домішки Fe3+ в структурі скла. Досліджено також вплив попередньої обробки у розчинах NaCI і модельної фізіологічної рідини на процеси формування радіаційних парамагнітних дефектів у біологічно-активних стеклах. Визначено параметри спін-гамільтоніана і термічну стабільність радіаційних центрів. Обговорюються електронна структура, особливості формування і можливі моделі радіаційних парамагнітних центрів у структурі біологічного скла

Intrinsic Luminescence of the Undoped Glasses of (CaO-Ga2\text{}_{2}O3\text{}_{3}-GeO2\text{}_{2}) System

For the first time the intrinsic luminescence in the undoped (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) glasses with different composition has been found and investigated in the 80÷300 K temperature range. The new glasses of high chemical purity and optical quality with stoichiometric composition similar to that in calcium-gallium- germanium garnet (Ca$\text{}_{3}$Ga$\text{}_{2}$Ge$\text{}_{3}$O$\text{}_{12}$), trigonal Ca-gallogermanate (Ca$\text{}_{3}$Ga$\text{}_{2}$Ge$\text{}_{4}$O$\text{}_{14}$), and Ca$\text{}_{3}$Ga$\text{}_{2}$O$\text{}_{6}$ crystals were obtained by the high-temperature synthesis method. The luminescence and photoexcitation spectra analysis, supported by EPR spectroscopy data, yields the following results: (i) the UV-excited non-elementary broad emission band with maxima at roughly 500 nm and 420 nm in the (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) glasses is due to recombination of ensemble of the transient hole O$\text{}^{-}$ centres; (ii) the emission bands with maxima at nearly 380 and 710 nm, which were distinctly revealed in glasses with the Ca$\text{}_{3}$Ga$\text{}_{2}$Ge$\text{}_{4}$O$\text{}_{14}$ and Ca$\text{}_{3}$Ga$\text{}_{2}$O$\text{}_{6}$ compositions, are assigned to the luminescence of UV-induced electron centres of two different types. Possible models of the luminescence centres in (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) glass network are discussed