Determining the enthalpy and specific heat of magnesia spinels in the range 1400–2200°K

Conclusions Temperature functions were obtained for H(T) and C_p(T) which can be used for calculating the thermodynamic functions of the spinels MgAl₂O₄ and MgCr₂O₄ in the temperature regions of their service (up to 2200°K), to supplement the existing relationships (up to 1800°K).Translated from Ogneupory, No. 6, pp. 9–12, June, 1979.     

Studies on the oxidative and hydrolytic destruction of peat

This article contains a brief survey of scientific studies on the chemical processing of peat with the use of its acid hydrolysis and oxidation in an alkaline medium carried out in Belarus. It was shown that the use of these classical methods for the chemical destruction of the natural polymers of peat makes it possible to obtain a wide spectrum of biologically active preparations.     

Anhysteretic magnetization reversal of spin valves with a strong and weak interlayer coupling

The hysteresis of magnetoresistance has been studied as a function of the angle between the magnetic field applied in the plane of layers and the easy axis for spin valves with the composition [Ta, (Ni₈₀Fe₂₀)₆₀Cr₄₀] /Ni₈₀Fe₂₀/Co₉₀Fe₁₀/Cu/Co₉₀Fe₁₀/Mn₇₅Ir₂₅/Ta. In spin valves with a strong interlayer coupling at a small deviation of the magnetic-field direction from the easy axis there was revealed a sharp (to a few tenths of an oersted) narrowing of the hysteresis loop of the magnetization reversal of the free layer. Based on an analysis of the angular dependences of the hysteresis, critical angles at which a change occurs in the mode of the magnetization reversal have been determined. In terms of the Stoner-Wohlfarth model of the coherent rotation of the magnetization, the angles at which a transition to an anhysteretic magnetization reversal is observed have been estimated theoretically for the spin valves with a strong interlayer coupling.     

Spin-flop states in a synthetic antiferromagnet and variations of unidirectional anisotropy in FeMn-based spin valves

Spin valves with a synthetic antiferromagnet have been prepared by magnetron sputtering. Regularities of the formation of single- and two-phase spin-flop states in the synthetic antiferromagnet have been studied using magnetoresistance measurements and imaging the magnetic structure. A thermomagnetic treatment of spin valve in a field that corresponds to the single-phase spin-flop state of synthetic antiferromagnet was shown to allow us to obtain a magnetically sensitive material characterized by hysteresis-free field dependence of the magnetoresistance.     

Crystal structure and magnetic properties of Fe/Cr/Gd superlattices

Results of investigations of structural and magnetic properties of Fe/Cr/Gd superlattices that differ in the thicknesses of the Cr interlayer have been reported. The insertion of the Cr interlayer between Gd and Fe layers has been found to lead to structural changes in Gd layers and the appearance of an additional fcc phase in them along with the main hcp phase. The new fcc phase is uniformly distributed across the thickness of the layer and is not localized near layer boundaries or in the center of Gd layers. Polarized-neutron reflectometry was used to show that the aforementioned structural changes are accompanied by a substantial (two-fold to threefold) decrease in the average magnetization of gadolinium over a wide temperature range. Near interfaces of the Gd layer, a layer appears that is two-to-three monatomic layers thick and characterized by increased magnetic moment.     

Control of Low-Field Hysteresis Loop Shift of Spin Valves

Spin valves that comprise synthetic antiferromagnet as a component of pinned layer and an exchange-coupled ferromagnet/Ru/ferromagnet structure in the free layer have been prepared by magnetron sputtering. Microobjects have been formed from spin valves by optical and electron-beam lithography. It has been shown that the shift of the low-field magnetoresistance hysteresis loop decreases as the thicknes of the Ru spacer in the free layer of spin valve increases. The almost hysteresis-free odd-field dependences of the magnetoresistance were obtained for micron-sized samples; in this case, the sensitivity is 0.2%/Oe.     

Influence of high-velocity impact on metals

The work is devoted to investigation of metals’ behavior under shock loading. The materials under investigation were copper, aluminum, lead, titanium, titanium alloys and different steels. Microstructure investigations have been carried out using optical microscopy. The strength behavior was investigated with the help of a microhardness device. Comparison of the spherical action of waves and uniaxial shock loading for the aforementioned metals has been done.     

Genetic identification of Saccharomyces bayanus var. uvarum, a cider-fermenting yeast

Twenty-one Saccharomyces strains isolated from a cider process were analysed in terms of karyotypes, Y' S. cerevisiae sequence occurrence, rDNA structure and cross-fertility with species tester strains. A strong predominance of S. bayanus var. uvarum G. Naumov was found (18 strains vs. three S. cerevisiae). Among the S. bayanus var. uvarum, only three strains proved to contain species-specific Y' S. cerevisiae sequences.     

Group composition and properties of petroleum wax fractions

The group chemical composition and physicomechanical properties of petroleum wax fractions are investigated. The mechanism of their change with an increase in the average distillation temperature is determined.Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 47 – 48, January – February, 2005.