60 research outputs found
Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy
The magnetization processes in binary magnetic/nonmagnetic amorphous alloy
Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic
hysteresis loops, temperature dependence of magnetization, relaxation of
magnetization and magnetic ac susceptibility, including a nonlinear term.
Blocking of magnetic moments at lower temperatures is accompanied with the slow
relaxation of magnetization and magnetic hysteresis loops. All of the observed
properties are explained with the superparamagnetic behaviour of the single
domain magnetic clusters inside the nonmagnetic host, their blocking by the
anisotropy barriers and thermal fluctuation over the barriers accompanied by
relaxation of magnetization. From magnetic viscosity analysis based on thermal
relaxation over the anisotropy barriers it is found out that magnetic clusters
occupy the characteristic volume from 25 up to 200 nm3 . The validity of the
superparamagnetic model of Hf_{57}Fe_{43} is based on the concentration of iron
in the Hf_{100-x}Fe_{43} system that is just below the threshold for the long
range magnetic ordering. This work throws more light on magnetic behaviour of
other amorphous alloys, too
Two-step transition in a magnetoelectric ferrimagnet Cu2OSeO3
We report a detailed single crystal investigation of a magnetoelectric
ferrimagnet Cu2OSeO3 using dc magnetization and ac susceptibility along the
three principal directions [100], [110] and [111]. We have observed that in
small magnetic fields two magnetic transitions occur, one at Tc = 57 K and the
second one at TN = 58 K. At Tc the non-linear susceptibility reveals the
emergence of the ferromagnetic component and below Tc the magnetization
measurements show the splitting between field-cooled and zero-field-cooled
regimes. Above 1000 Oe the magnetization saturates and the system is in a
single domain state. The temperature dependence of the saturation below Tc can
be well described by m(T) = m(0)[1 - (T/Tc)^2]^{\beta}, with m(0) = 0.56
(mu)B/Cu, corresponding to the 3-up-1-down configuration. The dielectric
constant measured on a thin single crystal shows a systematic deviation below
the transition, indicating an intrinsic magnetoelectric effect.Comment: accepted for publication in PR
Occurrence of hydrocyanic acid in the process of briquetting of ferrosilicon and rhodanate concentrations in the urine of exposed workers
Site-selective quantum correlations revealed by magnetic anisotropy in the tetramer system SeCuO3
We present the investigation of a monoclinic compound SeCuO3 using x-ray
powder diffraction, magnetization, torque and electron-spin-resonance (ESR).
Structurally based analysis suggests that SeCuO3 can be considered as a 3D
network of tetramers. The values of intra-tetramer exchange interactions are
extracted from the temperature dependence of the susceptibility and amount to
~200 K. The inter-tetramer coupling leads to the development of long-range
antiferromagnetic order at TN = 8 K. An unusual temperature dependence of the
effective g-tensors is observed, accompanied with a rotation of macroscopic
magnetic axes. We explain this unique observation as due to site-selective
quantum correlations
Analysing radionuclide content in soil samples and radiological risks in the clayey material surrounding of the “Zbegovi” deposit, Donje Crniljevo, Serbia
This paper presents the results of analyses of radionuclide content in the samples of the surrounding soil and clayey material of “Zbegovi” open-pit mine in Donje Crniljevo, Serbia. Samples from 78 sites were collected and prepared. The activity concentrations were determined for radionuclides: 238U, 232Th, 40K, 226Ra, and 137Cs. The mean values obtained are as follows: 23 Bqkg–1, 89 Bqkg–1, 372 Bqkg–1, 56 Bqkg–1, and 11 Bqkg–1, respectively. Concentrations of 238U, 40K, and 226Ra in the studied area do not deviate from the values obtained for the soil in Serbia. The concentration of 232Th in the studied area is slightly higher relative to average values for soil, and slightly lower compared to similar deposits of clayey material in the world. Measurements performed showed that the open-pit mine of clayey material is completely uncontaminated surface as far as 137Cs is concerned, while there are sites where measured 137Cs concentrations are significantly higher, which is due to topographic differences and inhomogeneous surface contamination of land after the Chernobyl accident. To assess the radiological risks in the observed area, the following indices were determined: absorbed dose rate, annual outdoor effective dose, absorbed dose for biota, excess lifetime cancer risk outdoors as well as external radiation hazard index. The mean value of the estimated absorbed dose rate in the given area amounts to 80.1 nGyh–1, and the annual outdoor effective dose ranges from 46.9 to 134 Sv. Absorbed dose rate for biota in the studied area is 1.31 10–4 Gyd–1. The mean excess lifetime cancer risk outdoors for the population is 3.8 10–4, and t he mean value of the external radiation hazard index obtained in this study is 0.48, which is consistent with the world average. A low dose of radiation will not pose a risk to the population and biota in the studied area
Low temperature magnetic transition in RuSr2EuCeCu2O10 ruthenocuprate
A new magnetic transition in the ruthenocuprate parent compound
RuSr2EuCeCu2O10 has been observed below 10 K. It shows up only as a kink in the
imaginary part of the ac susceptibility and exhibits a pronounced frequency
dependence. At the same time, the real part of the ac susceptibility and the dc
magnetization study show very little change in the same temperature window
suggesting only a minor fraction of the material to be involved in the
transition. Frequency dependence shows excellent agreement with the predictions
of the Arrhenius law known to describe well the dynamics of the
superparamagnetic particles. The same type of the investigation on the
RuSr2Eu1.1Ce0.9Cu2O10 composition showed no evidence of the similar transition,
which points to a possible intrinsic behavior.Comment: to be published in Physica
Triticum aestivum ir T. durum genetiniai parametrai kokybės technologinėms savybėms Serbijoje
Proteins are important in determining the nutritional value of wheat, and among them gluten determines the baking quality of bread wheat and pasta-making technological properties of wheat. By assessing genetic parameters of wheat quality traits, it is possible to elucidate potential for improvement. The plant material consisted of 30 genotypes of bread and durum wheat of worldwide origin. The trials were sown at three locations in Serbia during two vegetation seasons 2010-2011 and 2011-2012. Protein content, wet gluten content, Zeleny sedimentation volume and deformation energy were determined by near infrared spectrometry. The objectives of this investigation were to assess: i) variability, components of variance, heritability in a broad sense (hb2)expected genetic advance for protein content, wet gluten content, Zeleny sedimentation volume and deformation energy; ii) associations between agronomic characteristics and protein content, wet gluten content, Zeleny sedimentation volume and deformation energy in order to determine indirect selection feasibility. In durum wheat, the highest coefficients of genetic and phenotypic variation (CVg and CVph) were recorded for deformation energy in bread wheat (18% and 18.4%, respectively), whereas the lowest values of 4.1% and 4.6% were shown for protein content. The relation genetic component of variance (σg2)/component of variance due to genotype × environment interaction (σge2) < 1 was observed for protein content (3.2), wet gluten content (2.9) and deformation energy (3.9), and equal to one for Zeleny sedimentation volume, in bread wheat. In durum wheat, σge2/σg2< 1 was detected for protein content (1.4), wet gluten content (1.5), Zeleny sedimentation volume (2.1) and deformation energy (1.4). Considering very high and high hb2 observed for deformation energy and Zeleny sedimentation volume (95.8% and 86.2%, respectively) in bread wheat, coupled with high genetic advance (36.3% and 28.1%, respectively), success from classical breeding can be anticipated. Grain thickness was strongly associated with Zeleny sedimentation volume, and to a lesser extent with protein content, wet gluten content and deformation energy in bread and durum wheat, and along with grain vitreousness in durum wheat, can serve for indirect selection
Magnetic excitations and electronic interactions in SrCuTeO: a spin-1/2 square lattice Heisenberg antiferromagnet
SrCuTeO presents an opportunity for exploring low-dimensional
magnetism on a square lattice of Cu ions. We employ ab initio
multi-reference configuration interaction calculations to unravel the Cu
electronic structure and to evaluate exchange interactions in SrCuTeO.
The latter results are validated by inelastic neutron scattering using linear
spin-wave theory and series-expansion corrections for quantum effects to
extract true coupling parameters. Using this methodology, which is quite
general, we demonstrate that SrCuTeO is an almost realization of a
nearest-neighbor Heisenberg antiferromagnet but with relatively weak coupling
of 7.18(5) meV.Comment: 10 pages, 7 figure
Interplay between the structural and magnetic probes in the elucidation of the structure of a novel 2D layered V_4O_4(OH)_2(O_2CC_6H_4CO_2)_4·DMF
The title compound has been synthesized under solvothermal conditions by reacting vanadium(V) oxytriisopropoxide with terephthalic acid in N,N-dimethylformamide. A combination of synchrotron powder diffraction, infrared spectroscopy, scanning and transmission electron microscopy, thermal and chemical analysis elucidated the chemical, structural and microstructural features of new 2D layered inorganic-organic framework. Due to the low-crystallinity of the final material, its crystal structure has been solved from synchrotron X-ray powder diffraction data using a direct space global optimization technique and subsequent constraint Rietveld refinement. [V_4O_4(OH)_2(O_2CC_6H_4CO_2)_4•DMF] crystallizes in the monoclinic system (space group P2/m (No. 10)); cell parameters: a = 20.923(4), b = 5.963(4), c = 20.425(1)Å, β = 123.70(6)º, V = 2120.1(9)Å^3, Z = 2. The overall structure can be described as an array of parallel 2D layers running along [-101] direction, consisting of two types of vanadium oxidation states and coordination polyhedra: face-shared trigonal prisms (V^4+) and distorted corner-shared square pyramids (V^5+). Both configurations form independent parallel chains oriented along the 2-fold symmetry crystallographic b-axis mutually interlinked with terephthalate ligands in a monodentate mode perpendicular to it. The morphology of the compound exhibits long nanofibers, with the growth direction along the layered [-101] axis. The magnetic susceptibility measurements show that the magnetic properties of V_4O_4(OH)_2(O_2CC_6H_4CO_2)_4•DMF can be described by a linear antiferromagnetic chain model, with the isotropic exchange interaction of J = −75 K between the nearest V^4+ neighbours of S = 1/2
- …