In this paper we consider the existence of W01,1Ω solutions to following kind of problems −div∇up−2∇u/1+uθp−1=fx,x∈Ω;ux=0,x∈∂Ω where Ω is an open bounded subset of RNN>2, maxp−2N+1/p−1N−1,0<θ<1 and ...1<p⩽1+N−1/N1−θ+θ, f is a function which belongs to a suitable integrable space.
Norway’s geopolitical position as both a neighbour of Russia and a member of NATO places it at the forefront of Moscow’s self-assertive and aggressive foreign and security policy. However, Norway’s ...NATO membership reduces Russia’s room for manoeuvre to actions below the threshold of armed conflict. In this article, Runar Spansvoll examines how Russia has made use of such aggressive and coercive sub-threshold activities in the political, information and military domains between 2014–23 in a campaign to compel Oslo to comply with its foreign and security policy objectives.◼
Die Verstärkung der magnetischen Kopplung in 4f‐basierten Einzelmolekülmagneten ist eine Herausforderung. In ihrem Forschungsartikel auf S. 24408 setzen Akseli Mansikkamäki, Muralee Murugesu und ...Mitarbeiter stark delokalisierte Tetrazinyl‐Radikale zur Verbrückung von 4f‐Metallocenen ein, um vierkernige Komplexe zu bilden. Eine gründliche Untersuchung der magnetischen Eigenschaften und theoretische Studien stützen ein radikalinduziertes “Giant‐Spin”‐Modell mit starken Austauschwechselwirkungen, SMM‐Verhalten bei Nullfeld und einem Koerzitivfeld von 3 T.
Researchers are taking great interest in the synthesis and characterization of MnZn ferrites due to their wide range of applications in many areas. MnZn ferrites are a class of soft magnetic ...materials that have very good electrical, magnetic and optical properties. The properties of MnZn ferrites include high value of resistivity, permeability, permittivity, saturation magnetization, low power losses and coercivity. The above mentioned advantageous features of MnZn ferrites make them suitable for the use in various applications. In biomedical field these ferrites are used for cancer treatment and MRI. MnZn ferrites are also used in electronic applications for making transformers, transducers and inductors. These ferrites are also used in magnetic fluids, sensors and biosensors. MnZn ferrite is highly useful material for several electrical and electronic applications. It finds applications in almost every household appliances like mobile charger, LED bulb, TV, refrigerator, juicer mixer, washing machine, iron, microwave oven, mobile, laptop, desktop, printer and so on. Therefore, the present review focuses on different techniques for synthesis of MnZn ferrites in literature, their characterization tools, effect of doping on the properties of MnZn ferrite and finally we will discuss about their applications.
This work investigates the influence of niobium pentoxide (Nb2O5) as dopant, on the structural, magnetic, and dielectric properties of NiZnCo ferrites. The results showed that Nb2O5 was an effective ...dopant, and the Nb5+ ions entered the B site to replace Fe3+ ions, which altered the electromagnetic properties of the NiZnCo ferrite. In particular, the coercivity (Hc) was 20∼24 Oe, and the magnetic quality factor (Q), was more than 200 at x = 0 and x = 0.1 wt%, which is 4∼5 times higher than that of NiZn and NiCuZn ferrites. Excellent electromagnetic properties were obtained for 0.1 wt% Nb2O5-doped NiZnCo ferrite, i.e., Ms = 88.3 emu/g, Hc =20.4 Oe, ρ = 2.4 × 105 Ω m and Q = 202 @20 MHz. These excellent electromagnetic properties of Nb2O5-doped NiZnCo ferrites could be potentially applied to resonators and capacitors at high frequency.
We investigated the microstructural and magnetic properties of nanocrystalline FeCuNbSiB thin films produced through magnetron sputtering followed by heat treatment. Our research focused on film ...thicknesses (80 nm and 160 nm) and heat treatment temperatures (490 °C–520 °C) that resulted in samples characterized by low coercivity and high effective magnetization. Conducting a comprehensive microstructural examination, we employed X-ray diffraction and transmission electron microscopy techniques, including selected area electron diffraction, high-resolution imaging and Fourier transform analysis. Magnetic properties were investigated using an alternating gradient field magnetometer and broadband ferromagnetic resonance. Structural analysis revealed, for all our heat-treated films, a well-defined microstructure characterized by nanograins, with a Fe3Si ferromagnetic phase, embedded within an amorphous matrix. Our films exhibit sub-Oe coercivity, reaching as low as 0.51 Oe, along with an increase in effective magnetization from 1170 emu/cm3 for the amorphous phase to a maximum of 1260 emu/cm3 in the nanocrystalline phase.
•FeCuNbSiB thin films were produced through magnetron sputtering, then heat treated.•The Fe3Si phase was obtained with crystallite sizes ranging from 11 nm to 15 nm.•Crystallization resulted in sub-Oe coercivity and increased effective magnetization.•Magnetic properties were investigated using AGFM and broadband-FMR techniques.
A systematic study of the dependence of the Grain Boundary Diffusion Process (GBDP) on texture using Dy and Dy-Nd-Cu in microcrystalline sintered and nanocrystalline hot deformed Nd-Fe-B magnets was ...performed. Diffusion parallel or perpendicular to the texture direction, the nominal c-axes orientation in the polycrystals, was investigated. By measuring thin slices from the respective samples, coercivity as a function of (i) magnet thickness and (ii) diffusion depth was obtained showing that GBDP efficiency depends on the diffusion direction, diffusion source as well as the grain morphology originating from the magnet production route. In nanocrystalline hot deformed magnets perpendicular diffusion is superior due to the platelet-like shape of the grains. Microcrystalline sintered magnets consist of equiaxed grains hence the main effects originate in anisotropic lattice diffusion and pole surface hardening. The magnetic properties are correlated with a comprehensive analysis of microstructure, chemistry and magnetization reversal.
•Comparing texture's effect on GBDP in Dy, Dy-Nd-Cu in microcrystalline sintered & nanocrystalline hot deformed magnets.•GBDP efficiency relies on diffusion direction, source, and grain morphology from the magnet production route.•Perpendicular diffusion is more effective in hot deformed (nanocrystalline) magnets due to their platelet-like grain shapes.•Comprehensive analysis links magnetic properties with microstructure, chemistry, and magnetization reversal studies.
Post-sinter annealing effects on the structure and coercivity have been investigated for the (Zr, Ti)-doped Nd-Ce-Fe-B sintered magnets. In them, an in-situ formed Zr-rich Zr-Ti phase with the strip ...shape is found to be beneficial for the coercivity Hcj, because its distribution along grain boundaries (GBs) after annealing at 700℃ can block the magnetic domain within matrix phases passing through the adjacent RE2Fe14B grains. It, coupled with the optimized distribution of RE-rich phase, accounts for the 21.1 % increase of Hcj before and after annealing at 700 ℃. This temperature much higher than the melting-point (465 ℃) of RE-rich phase is the optimum annealing temperature, at which the RE-rich liquid phase is good for the distribution of Zr-Ti phase along GBs rather than at triple junction regions, optimizing GB microstructure. Such new findings deepen the understanding on microstructure evolutions of the GB modified Nd-Fe-B magnet during annealing and further provide a theoretical basis for the Hcj improvement.
•In-situ formed Zr-Ti phase with strip shape can increase coercivity of (Zr,Ti)-doped Nd-Ce-Fe-B magnets.•Coercivity can be increased by 21.1 % before and after annealing at 700 ℃.•Magnet structure evolution during annealing and its effect mechanism on coercivity were clarified.
With their excellent magnetic performance, Nd-Fe-B magnets have a large share of the permanent magnet market, even after the sudden rise in the price of rare earths in 2011, which have been supported ...by magnet manufacturers' efforts to save heavy rare earths. The demand for high performance magnets is expected to increase, and both magnet users and manufacturers therefore welcome alternative magnets containing less or no rare earths. A knowledge of thermodynamics and understanding of the mechanism of coercivity of Nd-Fe-B may become very useful to develop processes for new magnets. Furthermore, cost-performance must never be neglected in practical use.
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