We studied the giant magnetoimpedance (GMI) effect and magnetic properties of amorphous Co-rich magnetic microwires prepared by the Taylor-Ulitovski technique. The magnetic field dependence of ...impedance and the magnetic anisotropy fields can be tailored through the magnetoelastic anisotropy by controllable change of the internal stresses. Co-rich microwires exhibit high (above 300) GMI effect even at gigahertz frequencies. Features of the high-frequency GMI effect were analyzed using a ferromagnetic resonance-like approximation.
We studied the effect of applied tensile stresses on magnetic properties of Fe- and Co-rich amorphous glass-coated microwires. Rising of magnetic anisotropy field upon tensile stress in Co-rich ...glass-coated microwires is described by a linear dependence. Furthermore, decrease of magnetic susceptibility upon tensile stress is observed in Co-rich microwires. A monotonous increase in the coercivity and the switching field upon tensile applied stress is observed for as-prepared Fe-rich microwire. Stress induced magnetic bistability consisting of transformation of hysteresis and onset of rectangular hysteresis loop upon tensile stress, σ, of about 22.5 MPa is observed in stress-annealed Fe-rich microwires. Such stress-induced magnetic bistability results in considerable growing of coercivity and remanent magnetization in stress-annealed Fe-rich microwires. The rising in the coercivity and the switching field upon applied tensile stresses in stress-annealed Fe-rich microwires with stress induced magnetic bistability (at σ > 22.5 MPa) is roughly described by the σ½ dependence, as previously reported for the wires with spontaneous magnetic bistability. Consequently, stress-annealing of Fe-rich microwire allows beneficial enhancement of the stress dependence of coercivity. Observed dependencies are discussed considering stress dependence of the magnetostriction coefficient in Co-rich glass-coated microwires, internal stresses redistribution and domain structure rearrangement in stress-annealed Fe-rich microwires upon applied tensile stresses.
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•Linear increase in the magnetic anisotropy field upon stress in Co-rich microwires.•Decrease in the magnetic susceptibility upon applied stress in Co-rich microwires.•Observation of stress induced magnetic bistability in stress-annealed Fe-rich microwires.•Enhanced stress dependence of coercivity in stress-annealed Fe-rich microwires.•Observation of σ½ dependence of switching field in stress-annealed Fe-rich microwires.
We report on the fabrication, and the magnetic and structural properties of novel glass-coated Ni
50.95Mn
25.45Ga
23.6 microwires with a metallic core diameter of 44
μm and a total diameter of 82
μm ...prepared by the Taylor–Ulitovsky method. These annealed microwires showed ferromagnetic behaviour with a well-defined easy axis that corresponds to the axis of the wire. X-ray diffraction confirmed a tetragonal
martensitic structure with a lattice parameters a
=
3.75
Å and c
=
6.78
Å. The Curie temperature was estimated to be ∼315
K. The maximum entropy change at the magnetic transition was −0.7
J
kg
−1
K
−1.
Domain wall (DW) propagation and magnetic properties in as-prepared and annealed Fe- and Fe-Ni-rich microwires are experimentally studied. Observed DW dynamics is discussed considering the effect of ...magnetoelastic anisotropy, internal stresses relaxation after annealing and domain wall stabilization owing to pair ordering. Additionally, modification of the magnetostriction coefficient related to stress relaxation and formation of nanocrystalline structure after annealing are considered. Annealing allows considerable improvement of DW velocity in Fe-rich and Fe-Ni based (low Ni content) microwires. In Fe-Ni-based microwires the DW velocity increasing is less appreciated. Moreover coercivity increasing after annealing of Fe-Ni based microwires is observed.
Consequently, annealing is the effective method for engineering of the DW dynamics in glass-coated microwires.
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•Rectangular hysteresis loops of Fe and Fe-Ni based microwires.•Enhancement of domain wall velocity after annealing.•Dependences of domain wall mobility on annealing time.•Negative critical propagation field values in as-prepared microwires.
The domain wall (DW) propagation in magnetically bistable Fe74Si11B13C2 amorphous microwires with metallic nucleus diameters of 12–16μm has been investigated in order to explain high DW velocities ...observed in Sixtus–Tonks like experiments. In micrometric wires, the boundary between two head-to-head domains is very elongated. The DW mobility normal to the wall surface is reduced by the domain aspect ratio and is in the range of a few m/s/Oe in the linear regime. The experimental results in the viscous regime could be quantitatively explained in terms of the domain length and normal mobility limited by the eddy currents and spin relaxation losses.
The rapid development of modern self-employment, the massive transition from employment to self-employment and vice versa is a challenge for traditional pension systems. The Organisation for Economic ...Co-operation and Development (OECD) responded by adopting compulsory state pension schemes for the self-employed shared with employees. Russia following global trends with a small-time lag, unlike others, provides an unconditional guarantee of social pensions. It is all the more important to study the advanced international experience in attracting the self-employed to pension insurance. This is
the aim
of the study. Research
tasks
are as follows: to identify different approaches to organizing pension insurance for the self-employed across OECD countries, to examine the mechanisms and factors arising, and to evaluate their performance.
The research method
is cluster analysis of the generated self-employed pensions parametric indicators database according to OECD data (2019–2021) (18 indicators as part of clustering, architecture, finance, performance factors) for 28 countries. The study identifies 3 clusters (approaches) to the organization of pension provision for the self-employed: 1 — employee-like mandatory contributions to state pension schemes; 2 — mandatory contributions with advantages; 3 — voluntary pension contributions with advantages. In general, none of the approaches can be called “the best”. The effectiveness of pension decreases with any form of low-income self-employed inclusion in income-based pension schemes, as well as dependent self-employment. The author
concludes
that for Russia alternative options for self-employed pensions are quasi-mandatory pension insurance, self-employed employee-like participation in voluntary funded pension schemes only, state co-financing, practical training in financial literacy without going into the depth of financial knowledge. Discussion for
further research
is a detailed study of the application of the results into self-employed pension insurance practice in Russia.
We studied the influence of AC current flowing through microwires, on magnetization dynamics. We used a previously developed Sixtus-Tonks modified setup to evaluate the domain wall (DW) velocity ...within the microwire. However, instead of a magnetizing solenoid, we used a current flowing through the microwire. We observed that the AC current flowing through the annealed Co-rich microwire leads to remagnetization by fast domain wall propagation. The estimated DW velocity was approximately 4.5 km/s, which is similar to and even higher than that reported for the magnetic-field-driven domain wall propagation in Fe- and Co-rich microwires. We measured the DW velocity under tensile stress, and found that the DW velocity decreases under applied stress. An observed DW propagation induced by the current flowing through the microwire is explained considering the influence of an Oersted magnetic field on the outer domain shell. This field has a circular easy magnetization direction and magnetostatic interaction between the outer circumferentially magnetized shell and the inner axially magnetized core.
The n-3 and n-6 polyunsaturated fatty acid (PUFA) families are essential for important physiological processes. Their major source are marine ecosystems. The fatty acids (FAs) from phytoplankton, ...which are the primary producer of organic matter and PUFAs, are transferred into consumers via food webs. Mollusk FAs have attracted the attention of researchers that has been driven by their critical roles in aquatic ecology and their importance as sources of essential PUFAs. The main objective of this review is to focus on the most important factors and causes determining the biodiversity of the mollusk FAs, with an emphasis on the key relationship of these FAs with the food spectrum and trophic preference. The marker FAs of trophic sources are also of particular interest. The discovery of new symbioses involving invertebrates and bacteria, which are responsible for nutrition of the host, deserves special attention. The present paper also highlights recent research into the molecular and biochemical mechanisms of PUFA biosynthesis in marine mollusks. The biosynthetic capacities of marine mollusks require a well-grounded evaluation.
Two nudibranch mollusks, Chromodoris sp. and Phyllidia coelestis, collected from tropical waters of the Northwestern Pacific, were analyzed for lipids. The aim of this study was to fill the gap in ...knowledge of lipid biochemistry of mollusks. Phospholipids (PL) were the dominating lipid class followed by sterols (13%). Neutral lipids were not detected in Chromodoris sp. By contrast, P. coelestis contained TAG, diacylglyceryl ether, long chain alcohol and esters of sterols. Among PL, PC was predominant (about 50%); PE, PS and CAEP were almost in equal proportions. Sixty five FA were identified as methyl esters and N-acyl pyrrolidides by GC-MS. The sea slugs exhibited a wide diversity of FA. The common marine n-3 PUFA, 20:5n-6 and 22:6n-3, constituted 0.6-1.3% of the total FA, whereas n-6 PUFA, 22:4n-6, 20:4n-6, and 18:2n-6, were the main (25%). Among monounsaturated FA, 7-21:1 was the main (up to 6.2%). The non-methylene-interrupted (NMI) FA were found (9.4 and 12.4%), including the known 5,11-20:2, 5,13-20:2, 7,13-22:2, 7,15-22:2 and a novel isomer 7,13-21:2 (up to 3.9%). The pathway of its biosynthesis was suggested. A series of very long chain FA (VLC FA), with the main 5,9-25:2 and 5,9-26:2, were identified. High level of VLC FA (8.7 and 11.7%) in sea slugs is apparently the result of predation on sponges. Another unique feature concerned a high abundance of various odd and branched FA (16.7 and 34%), which could have originated from the dietary origin or symbiotic bacteria. This is the first report on lipid and FA composition of nudibranchs.
•Preparation of NiMnGa Heusler-type microwires.•A systematic study of magnetic properties of NiMnGa microwires.•Observation of MCE effect in NiMnGa microwires.•Discussions of the effect of internal ...stresses on properties of NiMnGa microwires.•Discussions of the effect of internal stresses on structure of NiMnGa microwires.
We studied magnetic properties, structure and magnetocaloric effect (MCE) in thin NiMnGa glass-coated microwires. After annealing studied microwires exhibit ferromagnetic behavior at room temperature. We directly measured the temperature change, ΔT, originated from the MCE in annealed NiMnGa glass-coated microwires and after glass removal. After glass removal ΔT increases from 0.06–0.08K to 0.22K. Observed temperature dependence of magnetization and MCE should be associated with both magnetic (paramagnetic–ferromagnetic) and structural (austenite–martensite) phase transitions. Considerable magnetization increase in vicinity of Curie temperature can be also attributed to the Hopkinson effect. We evaluated the possibility to prepare the magnetocaloric materials for magnetic refrigerators in the form of glass-covered microwires and showed that glass-coated microwires might be interesting for the MCE applications owing to high ratio of surface to volume.
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