Specific features of g ≈\approx 4.3 EPR line behavior in magnetic nanogranular composites

Films of metal-insulator nanogranular composites M$_x$D$_{100-x}$ with different composition and percentage of metal and dielectric phases (M = Fe, Co, CoFeB; D = Al$_2$O$_3$, SiO$_2$, LiNbO$_3$; x $\approx$ 15-70 at.%) are investigated by magnetic resonance in a wide range of frequencies (f = 7-37 GHz) and temperatures (T = 4.2-360 K). In addition to the usual ferromagnetic resonance signal from an array of nanogranules, the experimental spectra contain an additional absorption peak, which we associate with the electron paramagnetic resonance (EPR) of Fe and Co ions dispersed in the insulating space between the granules. In contrast to the traditional EPR of Fe and Co ions in weakly doped non-magnetic matrices, the observed peak demonstrates a number of unusual properties, which we explain by the presence of magnetic interactions between ions and granules

Effect of Cr spacer on structural and magnetic properties of Fe/Gd multilayers

In this work we analyse the role of a thin Cr spacer between Fe and Gd layers on structure and magnetic properties of a [Fe(35A)/Cr(tCr)/Gd(50A)/Cr(tCr)]x12 superlattice. Samples without the Cr spacer (tCr=0) and with a thin tCr=4A are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, SQUID magnetometery, magneto-optical Kerr effect and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4-300K and analysed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. The analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers

Magnetization and ferromagnetic resonance in a Fe/Gd multilayer: Experiment and modelling

Static and dynamic magnetic properties of a [Fe(35 Å<rf)/Gd(50 Å)]12 superlattice are investigated experimentally in the temperature range 5-295 K using SQUID magnetometery and the ferromagnetic resonance (FMR) technique at frequencies 7-38 GHz. The obtained magnetization curves and FMR spectra are analysed theoretically using numerical simulation on the basis of the effective field model. At every given temperature, both static and resonance experimental data can be approximated well within the proposed model. However, a considerable temperature dependence of the effective field parameter in gadolinium layers has to be taken into account to achieve reasonable agreement with the experimental data in the entire temperature range studied. To describe the peculiarities of experimental FMR spectra, a non-local diffusion-type absorption term in Landau-Lifshitz equations is considered in addition to the Gilbert damping term. Possible reasons for the observed effects are discussed. © 2017 IOP Publishing Ltd

Ant-aphid relations in Costa Rica, Central America (Hymenoptera: Formicidae; Hemiptera: Aphididae)

We present the first catalogue of ant-aphid associations (Hymenoptera: Formicidae / Hemiptera: Aphididae) of Costa Rica. 29 species of ants and 18 species of aphids establish 48 relationships. Those interactions seem not to be rare in Costa Rica

Фибриновые технологии в ускорении регенерации поврежденной кости в эксперименте

The processes of regeneration of the damaged rat bottom jaw bone after application of enriched platelets a fibrin clot were studied by morphological and radiovisiographic methods. After operation with use of fibrin technologies already after 1 week the bone tissue defect is filled by the merged islets of again generated bone. By second week after fibrin use the further formation of bone tissue in defect and formation of a bone callosity is noted.Морфологическими и радиовизиографическими методами изучали процессы регенерации поврежденного участка кости нижней челюсти крыс после заполнения дефекта костной ткани обогащенным тромбоцитами фибриновым сгустком. После операции с применением фибриновых технологий уже спустя 1 нед весь дефект костной ткани заполнен слившимися островками вновь сформированной кости. Ко 2-й нед отмечено дальнейшее замещение дефекта костной тканью и формирование костной мозоли