Hollow core Bragg fiber with antiresonant intermediate layer

By means of the transfer matrix method, the optical properties of fibers with a distinct intermediate layer between a hol-low core and periodic cladding are calculated. The periodic cladding consists of two types of the alternating layers. The intermediate layer has distinct thickness and refractive index. Depending on these parameters, the fiber can work in the single-mode or multi-mode regimes. In the multi-mode regime, the optical loss of the smallest loss mode can be de-creased by increasing the thickness of the layer. In the single-mode regime, the optical loss falls with a rise in the refrac-tive index of the intermediate layer. The optical properties of the fiber are determined by the antiresonance reflection from the intermediate layer and the Bragg reflection from the periodic cladding. Selecting the parameters of the interme-diate layer, the optical loss of the fiber in the single-mode regime can be reduced by an order of magnitude over the loss of the traditional Bragg fiber.Comment: 9 pages, 4 figure

Ueber die copulirten Harnstoffe

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Magnetocaloric properties of Gd(Co1-xFex)2 compounds, with x ≤ 0.60

In this paper the results of specific magnetization and magnetocaloric effect (MCE) measurements for Gd(Co1-xFex)2 system upon the Co substitution by Fe for the x = 0 ÷ 0.60 range are presented. Phase composition was controlled by X-ray diffraction analysis. MCE has been studied within the temperature range of 300-850 K in magnetic fields up to 17 kOe by the magnetic entropy change calculation (ΔSm). It was found that in contrast to the previously studied R(Co-Fe)2 compounds where R = Dy, Ho, Er, an ordinary symmetrical peak of ΔSm(T) in the vicinity of TC is observed for presented samples. Additionally, the MCE comparison of Gd(Co0.88Fe0.12)2 with that for the isostructural Gd(Ni0.88Fe0.12)2 compound having a plateau-like ΔSm temperature dependence is given. The obtained results are discussed. © 2018 The Authors, published by EDP Sciences.This work has been supported by the State contracts No. 3.6121.2017/8.9 between U FU and the Ministry of Education and Science of Russian Federation

Effect of alloying elements (Zr, Hf, Co), heat and mechanical treatment conditions on the phase composition and magnetic properties of SmFe11Ti compounds with ThMn12 structure

The results of thermomagnetic, metallographic and X-ray diffraction phase analysis as well as the measurements of specific magnetization (σs), Curie temperature (TC), coercive force (HC) of (Sm,M)(Fe,M)12-xTix alloys samples, where M = Zr, Hf, Co with the ThMn12 main phase structure (1-12) are presented. The effect of the annealing temperature and the cooling rate on the formation of 1-12 phase and its magnetic properties, including the effect of high-energy milling on the magnetic hysteresis properties and alloys structure are described. It was found that the highest magnetic characteristics such as σs = 112.6 emu/g and TC = 600°C are attained in the (Sm0.8Zr0.2)(Fe0.75Co0.25)11.4Ti0.6 alloy after its annealing at 1050 °C and rapid cooling. It is noted that a mechanical milling of the alloy leads to 1-12 phase amorphization which accompanied by an α-(Fe) or metal Co phases impurity formation. © 2018 The Authors, published by EDP Sciences.The work was supported by the State contracts No. 3.6121.2017/ 8.9 between UrFU and the Ministry of Education and Science of Russian Federation and by the Fund of assistance to development of small enterprises in scientific-technical sphere No. 11996GU / 017

Magnetic properties of R(Co0.88Fe0.12)2 quasi-binary compounds

In this paper the results of magnetic properties study for a series samples of R(Co0.88Fe0.12)2 type intermetallic compounds with a heavy rare-earth elements (R = Gd, Tb, Dy, Ho, Er) are presented. Such materials having a plateau-like temperature dependences of magnetic entropy change in the temperature range lower Curie point are considered as a promising functional materials for magnetic refrigerators. Their phase composition was controlled by X-ray diffraction analysis with a help of Bruker D8 Advance diffractometer. Magnetic field magnetization dependences - M(H) were measured using a SQUID magnetometer (MPMS-XL-7, Quantum Design) within the temperature range of 5 - 600 K in magnetic fields up to 5600 kA/m. The crystal lattice parameter - a, Curie temperature - TC, coercivity - Hc and residual magnetization - Mr values are analyzed as a functions of R-element atomic number. For compounds with Tb, Dy, Ho and Er the second picks on the high field susceptibility temperature dependences - χhf (T) were found in the temperature range lower their TC. © Published under licence by IOP Publishing Ltd.Ministry of Science and Higher Education of the Russian Federation№ 02.3.6121.2017/8.9This work has been supported by the State contract No. 3.6121.2017/8.9 between UrFU and Ministry of Science and High Education of Russian Federation, and by Act 211 Government of the Russian Federation, contract № 02.A03.21.0006

Magnetocaloric effect Gd(Ni0.99Fe0.12)2

This work has been supported by the State contracts No. 1362 between UrFU and the Ministry of Education and Science of Russian Federation and by the Fund of assistance to development of small forms enterprises in scientific-technical sphere No. 6576GU/2015