Search

International audience; Irradiation of the heterostructure glass/Ta/Pt/GdFeCo/IrMn/Pt by 50 fs ultra-short laser pulses causes local thinning of the film down to~12-30 nm depth. These pits are distinguished by Atomic Force Microscopy (AFM), while their stray magnetic fields were detected by Magnetic Force Microscopy (MFM). The crater was formed due to layer-by-layer evaporation of the material. No sign of melting was found in the vicinity of the crater at subthreshold laser fluence below 12-15 mJ/cm 2 , but exceeding of the threshold caused destruction of the layers. Energy-dispersive X-ray spectroscopy (EDX) revealed depletion of Gd, Fe and Co, responsible for magnetic properties of the subthreshold crater. The amplitude of the local MOKE signal decreased down to 1.7 times in the irradiated area, while thinning of the ferromagnetic layer was 1.1 times. No proportional change of magneti-zation was caused by bias effect of IrMn layer. Decreased elastic modulus was found inside the subthreshold crater in the irradiated areas. Laser engineering of the surface of GdFeCo thin films opens the way for local control of energy balance between magnetic anisotropy, exchange coupling and Zeeman energy and creation of separated sectors for capture, storage and analysis of the ferromagnetic nanoparticles.

New method for the synthesis of the mononuclear anionic iron dinitrosyl complexes (DNICs) as prospective agents for nitric oxide (NO) chemotherapy of oncological diseases has been developed. Mononuclear anionic DNIC of the composition (N2H5)+[Fe(SR)2(NO)2]- with R = 5-nitropyridinyl (I) has been synthesized by the reaction of aqueous solutions of Na2[Fе(S2O3)2(NO)2] and N2H5[SС5H3N2O2] salts. The latter one was synthesized by the reduction of bis-(5-nitro-pyridin-2-yl) disulfide with hydrazine hydrate in ethanol at T = 25 °C. Physical-chemical properties of the synthesized complex were studied by X-ray, SEM, IR-, EPR, Mossbauer spectroscopy and SQUID magnetometry in combination with DFT quantum-chemical calculation of molecular structure and spectroscopic properties. Complex I was found to generate NO in proton media without additional activation. The cytotoxicity of I to human tumor cells of various geneses, viz. ovarian cancer SKOV3, colon cancer LS174T and non-small cell lung cancer A549 was discovered for the first time.

The experimental study of the mandrel rod loading in the pipe production on an automatic mill has established an absence of the rod stability during the rolling. To eliminate such an event the design of the centering device for the mandrel’s rod was proposed as an element of intermediate rod supports on the rear table of the mill. In case of the rolling of pipes, which are characterized by higher values of the relation between a diameter and a wall thickness, the simulation of the process with the application of FEM has been carried out in order to understand reasons of occurrence of a forming flaw at the pipe rear end and to evaluate the influence of the rolling dies positioning on the size of flaws.

The ability of different yeasts to synthesize pyruvic acid (PA) from glycerol-containing substrates has been studied. The selected strain Yarrowia lipolytica VKM Y-2378 synthesized PA with α-ketoglutaric acid (KGA) as a byproduct. The content of KGA greatly depended on cultivation conditions. The minimal formation of the byproduct was provided by the limitation of yeast growth by thiamine (0.6 µg/g biomass); the use of ammonium sulfate (0.6%) as a nitrogen source; addition of glycerol to cultivation medium in 20 g/L portions; maintaining the cultivation temperature at 28 °C, pH of the cultivation medium at 4.5, and medium aeration between 55 and 60% of saturation; the optimal cultivation time was 48 h. The selected strain cultivated under such conditions in a fermenter with a waste glycerol from biodiesel production process synthesized 41 g/L PA with a yield of 0.82 g/g. The mechanism of PA production from glycerol-containing substrates in Y. lipolytica is discussed.

Effect of cell microbeads labelled with commercial α-Fe2O3 nanoparticles (NPs) on magnetic properties of MgO/CoFeB/Ta/CoFeB/MgO/GaAs spin valves and monolayer system MgO/CoFeB/MgO/GaAs was observed. Magnetic scattering field of α-Fe2O3 microbeads shifts critical magnetic field (CMF) of magnetization switching of free layer in spin valves. The CMF is controlled by energy balance of magnetic anisotropy, interlayer exchange coupling, Zeeman energy and scattering magnetic field of microbeads. Local magnetic field of microbeads and their effect on CMF were estimated accordingly with the magnetic profile of the surface scanned by magnetic force microscope. Magnetic instability of film magnetization caused by magnetic microbeads deposited on the spin valve surface was revealed.

Magnetically modulated PrDyFeCoB microwires containing periodical local magnetic labels of ~ 10 μm length are imprinted by single 120 ns laser impulse. Initially amorphous microwires is locally transformed by laser irradiation to nanocrystalline (PrDy)2(FeCo)14B1, and (PrDy)1(FeCo)2, (PrDy)1(FeCo)4B1 magnetic phases, possessing enhanced magnetic anisotropy. Alternating magnetic patterns imprinted by laser irradiation have magnetization component perpendicular to the microwire main axis. Fast imprinting of the magnetic microlabels allows one to design programmable microstructures.

There is a variety of transition metal and lanthanide complexes, which exhibit properties typical of Single Ion Magnets (SIMs) only in the presence of external DC magnetic field (the so-called field induced SIMs). Here we propose composite material, in which powder sample of field induced SIM based on the recently reported hexacoordinated Co(II) complex is mixed with ferromagnetic microparticles (MPs). Controllable residual magnetic field of MPs acts as internal magnetic field suppressing quantum tunneling of magnetization and making it possible to observe slow magnetic relaxation in the cobalt complex even in the absence of external magnetic field.

International audience; Magnetic configurations in synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer with strong perpendicular ani-sotropy have been systematically studied. Magnetization versus field hysteresis loop has been measured for different temperature ranging from 5 to 300 K. The applied field – temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer's magnetization reversal, interlayer exchange coupling, and Zeeman energy.

International audience; Magnetic configurations in Pt/Co/Ir/Co/Pt synthetic ferrimagnet bilayer of strong perpendicular anisotropy have been systematically studied. Magnetization versus field hysteresis loops have been measured for different temperatures ranging from 5 to 300 K. The applied field e temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer's magnetization reversal, interlayer exchange coupling, and Zeeman energy.

We considered the continuous cylindrical grinding wheel of the planetary transmission with the use of highly porous worm grinding wheels (single and multiple). The process of continuous grinding of teeth by the method of generating is characterized by high accurate of relative rotation of tool and workpiece gears. The developed technological model of the interaction of radial, axial and tangential movements of the feed was allowed to produce the grinding with high accuracy and productivity. The application of highly porous circles makes it possible to reduce thermal stress of process and to improve the cutting conditions. The increase in the number of passes of the grinding wheel and the increase of cutting speed reduces the impact of the thermal processes occurring during grinding of teeth by reducing the contact time between the workpiece and the tool. The treatment of the teeth of the satellites of the double grinding wheels improves performance of the process compared to the single pass on 26%. Statistical control of error radial runout of the teeth of the satellites indicates the high accuracy and stability of process of continuous grinding of teeth by the generating.

Magnetic anisotropy and interface exchange interaction were analyzed in α-Fe core microwire covered with PrDyCoFeB amorphous shell. The α-Fe/PrDyCoFeB core/shell microwires were grown by pendant drop melt extraction technique providing separation of the α-Fe and PrDyCoFeB phases during the ultrafast cooling. Low saturation field of the core ~100 Oe and high saturation field of amorphous shell ~10 kOe with zero coercivity were distinguished from angular dependences of the magnetic moment, recorded in low and high magnetic fields. Sharp decrease of the longitudinal magnetization, effective anisotropy field and magnetic susceptibility have been observed below the critical temperature, Tcrit = 240 K, in zero field. The Almeida-Thouless transition from ferrimagnetic state to Ising spin glass state has been revealed in PrDyCoFeB amorphous shell. Such spin reorientation transition is very attractive for magnetocaloric applications. We found exchange bias effect controlled by exchange coupling between ferromagnetic core and ferrimagnetic shell. The significance of the obtained data lies in possible applications of the core/shell microwires for tweezers with magnetic moment, stepwise changing in external field. Exchange bias in core-shell interface provides determined initial state of the microwire used as working media of field sensor. The sharp decrease of the magnetization associating with spin-reorientation transition looks very promising for magnetocaloric applications close to room temperature.

The concentration effect of charge carriers on the magnetic moment of ferromagnetic MnSb nanoclusters embedded in GaSbMn thin films is reported. High concentration of holes enhances the probability of their tunneling through the barrier between the semiconductor matrix and the MnSb nanocluster. Enrichment of the MnSb clusters by Mn2+ ions instead of Mn3+ enhances their ferromagnetism. Dynamics of magnetization relaxation of the MnSb clusters under applied magnetic field has been studied in the 8–300 K temperature range. Magnetic anisotropy constant ∼3.2·104 erg/cm3 has been determined. The fluctuation field HF = 7 Oe and the activation volume VA = 1.7·10−16 cm3 have been extracted from magnetic viscosity data.

The effect of oxalic and itaconic acids, the inhibitors of the isocitrate lyase, on the production of isocitric acid by the wild strain Yarrowia lipolytica VKM Y-2373 grown in the medium containing rapeseed oil was studied. In the presence of oxalic and itaconic acids, strain Y. lipolytica accumulated in the medium isocitric acid (70.0 and 82.7 g/L, respectively) and citric acid (23.0 and 18.4 g/L, respectively). In control experiment, when the inhibitors were not added to the medium, the strain accumulated isocitric and citric acids at concentrations of 62.0 and 28.0 g/L, respectively. Thus, the use of the oxalic and itaconic acids as additives to the medium is a simple and convenient method of isocitric acid production with a minimum content of citric acid.

The Si:B micro-crystals enriched with 29 Si isotope have been studied by high resolution nuclear magnetic resonance (NMR) in the 300–800 K temperature range. The recovery of nuclear magnetization saturated by radiofrequency impulses follows pure power-law kinetics at 300 K, while admixture of exponential relaxation takes place at 500 K. The power-law relaxation corresponds to direct electron–nuclear relaxation due to the inhomogeneous distribution of paramagnetic centers, while exponential kinetics corresponds to the nuclear spin diffusion mechanism. The inhomogeneous distribution of deformation defects is a most probable reason of the power-law kinetics of nuclear spin relaxation.

Nanostructured powders of terbium oxides were prepared by the thermal decomposition of terbium acetate at different temperatures. The powders were investigated by means of XRD, HRTEM, magnetic measurements, and IR spectroscopy. It has been found that the most likely composition of the oxides is Tb4O7, and the powders containing more than one crystalline phase. At low temperatures the prepared oxides exhibit antiferromagnetic ordering with the Weiss constants ranging from −14 to −22 K. At 2 K the effective value of total angular momentum per one Tb ion in the paramagnetic state J = 2.5 ± 0.1. The effects of the calcination temperature on the crystal structure, microstructure and magnetic behaviors of the samples are discussed in terms of that surface impurities presented in the nanocrystalline powders of Tb oxides influence the cation Tb4+/Tb3+ ratio in their crystal lattice.

The reaction of the neutral [Mn(salpn)C(CN)3(H2O)] (salpn2 − = N,N′-1,3-propylenebis(salicylideneiminato) dianion) with [FeIII(CN)6]3 − in the presence of strong oxidizer (NH4)2S2O8 yields a binuclear anion complex [NH3CH2CH2CH2NH3]2 +{[MnIII(salpn)(H2O)][FeIII(CN)6]}2 − (1). Its structure, DC and AC susceptibility have been studied. Frequency dependence of the AC susceptibility characteristic for single-molecule magnets has been found.

Surface roughness formed under pulse fiber laser radiation is represented as superposition of the suitable initial error profiles. It is conformed that superposition of this profiles forms the total surface micro geometry under pulse laser milling. Specific reasons forming initial error profiles are discussed. Physical model described the micro geometry forming process under pulse laser milling is formulated and confirmed.

Broadening of the 28Si, 29Si isotope distribution in the subsurface layers of Si:B single crystals under plastic deformation has been observed by secondary ion mass spectroscopy. The 28Si, 29Si profiles broaden with increasing dislocation density. Accompanying changes in the 29Si16O profile caused by plastic deformation have been found. The shift of the 29Si16O profile to the crystal bulk correlates well with the 29Si+ isotope redistribution. The uphill diffusion or dislocation movement is a possible driving force of Si and SiO redistribution, whereas selectivity of the isotopes in oxidation reaction is provided by singlet–triplet transitions in Si⋯O short living pairs.

New class of microwires based on rare-earth PrDyFeCoB alloy is developed. Chemical technique of the microwire tip designing is proposed. The α-Fe core microwire covered with amorphous shell provides stepwise switching between four magnetic states in external homogeneous magnetic field. Focusing of the stray field in the microwire tip was visualized. Bias field ~20 Oe, high saturation magnetization and attraction force up to 2000 pN, large field gradient and techniques of chemical sharpening provide novelty and significance of the obtained results.

In Pt/Co/Ir/Co/Pt synthetic ferrimagnet, non-monotonic magnetic relaxation (NMMR) caused by switching of external magnetic dependends on Co layer thicknesse and temperature. In this paper, we have varied thickness of one of the Co layers in the Pt/Co/Ir/Co/Pt synthetic ferrimagnet in the 0.6–1.0 nm range at fixed Co layer thickness of another layer 1.1 nm in the 50–300 K range to find experimental conditions for NMMR. We found interdependence between Co layer thickness tCo and temperature T providing NMMR. Energy balance between magnetic anisotropies and exchange interaction of the two Co layers stipulates linear dependence of nessecary T on tCo. Exsact expression limitating magnetic anisotropies of the thick and thin Co layers and predicting NMMR conditions in tCo - T space is proposed. Altough all mentioned results relates to experiments in permanent magnetic field, the contribution of the NMMR to the magnetic hysteresis loops recorded in sweeping magetic field was experimentally found. Obtained results can be used for wide family of synthetic ferrimagnets with perpendicular anisotropy.

The GA-insensitive dwarf genes, Rht-B1b (Rht1) and Rht-D1b (Rht2), have been used worldwide for reducing plant height, improving lodging resistance and grain yield since the Green Revolution. To explore new dwarf genes for wheat improvement, in this study, the effects of GA-responsive (GAR) dwarf gene, Rht14, on plant height related traits, agronomic traits, yield traits and quality traits were evaluated in durum wheat by F2:3 lines, F3:4 lines and F4:5 lines that derived from reciprocal crosses between the Rht14 donor Castelporziano (CP) and Langdon (L). These results indicated that Rht14 could reduce plant height by an average of 26.68 % and 27.68 % in the lines of CP × L and L × CP populations, respectively. Furthermore, both the length of peduncle and each internode were all significantly reduced, with the basal one as the most proportion and the peduncle as the largest difference. The flag leaf length, width and area increased significantly in dwarf lines. Rht14 did not affect most of the yield components, including number of tillers plant−1, number of fertile tillers plant−1, spikelet number spike−1, grain number spike−1, biomass plant−1, grain yield plant−1, while significantly decreased 1000-kernel weight. Rht14 didn’t affect the length of coleoptile and seedling root traits when compared with tall lines, indicating it may have the potential for good seedling establishment in the field. A negative effect of Rht14 on some quality traits was observed. The results indicate that GAR dwarf gene Rht14 represents a new alternative locus in breeding programs for improving population yield potential and lodging resistance in wheat.

The α-Fe core/PrDy-FeCo-B(48 at.%)α-Fe(52 at.%) shell and GdPrDy(FeCo)B microwires were grown by pendant drop melt (PDM) extraction technique. Single core–shell microwires of ~80–100 μm diameter and 2–20 mm length manifest rectangular hysteresis loops corresponding to ~100 Oe switching magnetic fields. Bistability of the microwires relates to single domain state of the α-Fe inner core revealed by scanning electron microscopy (SEM). Rare-earth amorphous PrDy-FeCo-B shell of the microwire scanned by magnetic force microscope (MFM) possesses magnetization reversal nuclei corresponding to the α-Fe inclusions. Interwire magnetic dipole interaction and scattering of microwire size change shape of the magnetic hysteresis loop and increase coercive field up to 983 Oe, in chaotic ensembles of the core–shell microwires. The GdPrDy(FeCo)B microwires of the same sizes with no Fe core possess “butterfly” type of the hysteresis loop of high coercivity ~20 kOe.

Triclinic and monoclinic polymorph modifications of the complex [Co(qu)2Br2] were obtained, and its molecular and crystal structures were determined by single crystal X-ray analysis. The magnetic anisotropy parameter D and g-tensor were estimated by SQUID measurements and ab initio (SA-CASSCF/NEVPT2) quantum-chemical calculations. The ligand field effect and magnetostructural correlations in the family of complexes [Co(qu)2X2] (qu = quinoline and X = NCS−, Cl−, Br− and I−) were analyzed. A correlation between the ligand field and the energies of the molecule excited states was revealed.

An application is considered of the extractive distillation flowsheets with partially thermally coupled columns for the separation of ternary azeotropic mixtures with the different type of vapor–liquid equilibrium diagrams. The feasible extractive distillation flowsheets with such columns are identified for all types of the ternary azeotropic mixture vapor–liquid equilibrium diagrams. The manifold of flowsheets is the search space to identify the optimal arrangement for the separation of the individual mixture. An applicability analysis of all possible extractive distillation flowsheets for all types of vapor–liquid equilibrium diagram decreases the number of feasible configurations for the selection of the optimal extractive distillation sequence for the mixture with unique vapor–liquid equilibrium diagram separation. For example, in the case of benzene–cyclohexane–toluene mixture distillation with N-methylpyrrolidone as an entrainer, only 10 extractive distillation flowsheets instead of 22 potential ones must be analyzed, calculated and optimized for the identification of the best extractive distillation arrangement.