Magnetic microstructure in the as suction cast Fe 69B 20Nb 2Hf 2Si 2Y 5 alloy was revealed by combined Lorentz-TEM and LM-STEM DPC analysis. The thin foil of the alloy was found to be composed ...primarily of the amorphous phase with few dendritic structures. Magnetic domains were found large in the µm range with an average domain wall width of 52 nm. The magnetic domain boundaries are easily mobile, what was confirmed by in situ applied magnetic field. The LM-STEM DPC complements the Lorentz-TEM analysis by providing details on the intensity and spatial distribution of the magnetization vector within the domains.
•A reduced model for domain wall dynamics of Néel-wall type is derived.•The front dynamics is driven by the mean curvature and relaxes to a planar interface in the absence of external fields.•The ...front migration velocity is linearly dependent on the external magnetic field when it is weak.•The results are consistent with Walker’s ansatz.
In this paper, we use the matched asymptotic analysis to derive a reduced model for domain wall dynamics within thin films of Néel-wall type in soft ferromagnets. It is found that the front dynamics is driven by mean curvature in the absence of external fields, and always relaxes to a planar interface where the one-dimensional ansatz is valid. The analysis predicts a linear dependence of front migration velocity on the field strength if the external magnetic field is weak, which is consistent with the result of Walker’s ansatz. Moreover, the derivation also identifies a regime where such an analysis fails, which corresponds to the Walker’s breakdown.
The ac losses induced by an alternating transport current in type-II superconductors is a well-known phenomenon, which still attracts much attention because of its intrinsic relevance for the proper ...development of practical applications. In the case of single core superconducting cables of cylindrical cross-section, it is possible to find exact analytical solutions at self field conditions, and it has been believed for nearly two decades that the use of an ideal soft ferromagnetic sheath with negligible magnetization losses will not affect the electromagnetic properties of the superconducting wire, and on the contrary due to the shielding magnetic properties of the ferromagnet, the total ac losses of the SC wire have to be reduced or as maximum they must be equal to the one for the bare superconductor at self-field conditions, what contraries the experimental evidences that show a non-negligible increase on the ac losses. In this paper, we explain the physical nature of this mysterious increase in the ac losses for rounded superconducting/ferromagnetic heterostrutures, which for the sake of generality, has been solved within the critical state theory, and a magnetic multipolar expansion that enables the direct coupling of the magnetostatic properties of the superconductor and an ideal soft ferromagnet. A significant increase in the transient electric field during excitation period has been observed, which might have utter implications on the adequate selection of insulation materials for superconducting/ferromagnetic heterostructures.
High-temperature ferromagnets are widely used on a practical level. Based on them, magnetic memory for computers and various types of magnetic field sensors are created. Therefore, bulk ingots and ...thin-film samples of ferromagnet manganese antimonide (MnSb) with a high Curie point are of great interest, both from the practical and fundamental sides. Manganese antimonide films are obtained in hybrid structures using molecular-beam epitaxy. The thickness of the films does not exceed tens of nanometers. Despite their high sensitivity to magnetic fields, their small thickness prevents them from being used as magnetic field sensors. The aim of this work was to synthesise thick bulk ingots of manganese antimonide crystalsand films with a thickness of ~ 400 nm on sitall and silicon substrates. MnSb crystals were synthesised using the vacuum-ampoule method and identified using XRD, DTA, and microstructural analysis. The results of studies of bulk samples indicated the presence of an insignificant amount of antimony in additionto the MnSb phase. According to the DTA thermogram of the MnSb alloy, a small endothermic effect was observed at 572 °C, which corresponds to the melting of the eutectic on the part of antimony in the Mn-Sb system. Such composition, according to previous studies, guaranteed the production of manganese antimonide with the maximum Curie temperature. A study of the magnetic properties showed that the synthesised MnSb crystals were a soft ferromagnet with the Curie point ~ 587 K. Thin MnSb films were obtained by an original method using separate sequential deposition in a high vacuum of the Mnand Sb metals with their subsequent annealing. To optimise the process of obtaining films with stoichiometric composition, the dependences of the thickness of metal films on the parameters of the deposition process were calculated. The temperature range of annealing at which the metals interact with the formation of ferromagnetic MnSb films was established, the films were identified, and their electrical and magnetic properties were measured
We report on impedance measurements in the Heusler compound Pd
2
MnSn, Gd metal and the re-entrant alloy Au
0.82
Fe
0.18
. Using a computational procedure, the real and imaginary components of the ...circumferential permeability could be determined from the complex impedance data. We show that the temperature dependence of the permeability is useful to study magnetic phase transitions, whereas valuable information on domain-wall motion and spin rotation processes may be obtained from appropriate analyses of the frequency and external magnetic field dependences of the complex permeability.
A series of polymeric complexes were prepared from Fe^2＋, Co^2＋ or Ni^2＋ and poly（Schiff base） （DAPcIPA）, which was obtained by polycondensation of 5,6-diamino-1,10-phenanthroline （DAP） with ...isophthalaldehyde （IPA）. The structures of the polymer and the polymeric complexes were characterized by IR, 1^H-NMR and elemental analysis. The magnetic behavior of these complexes was measured as a function of magnetic field strength （0-3.98 ~ 106 A/m） at 5 K and as a function of temperature （5-300 K） at a magnetic field strength of 2.39 × 10^6 A/re. Experimental results show that DAPcIPA-Ni^2＋, DAPcIPA-Co^2＋ are soft ferromagnets while DAPcIPA-Fe^2＋ exhibits features of an antiferromagnet.
The infinite initial susceptibility encountered in the micromagnetics computations of sufficiently small, amorphous ferromagnetic spheres is argued to be a real physical phenomenon, which may ...actually be realized in practice as a very large enhancement of the initial susceptibility of thin, amorphous ferromagnetic films, when they are subdivided into separate discs. The only difficulty is to make the films highly homogeneous, and to avoid mechanical strains as much as possible.
Infinite initial susceptibility is predicted in certain micro-magnetic computations of sufficiently small spheres and circular discs made of isotropic magnetic material. In this letter, it is argued ...that this result pertains only to perfectly round samples in the absence of thermal energy. It is expected, therefore, that much lower values of the initial susceptibility will be found on experimentally realizable samples at room temperature.
•Highly ordered L21 type heusler alloy film on cu substrate.•Near stoichiometric Co2FeSn films by electrodeposition.•High magnetic moment, high TC and high effective anisotropy films.•Co2FeSn films ...(320 nm −1400 nm thick) with high crystalline order.•Minority band gap close (∼0.05 eV) to fermi level.
Co2FeSn films have been electrochemically deposited on polycrystalline Cu substrates in potentiostatic mode. Processed films with thicknesses of 320 nm, 780 nm, and 1400 nm exhibited highly ordered L21 type crystal structure with saturation magnetizations of 1023.38 kA/m (5.08 ± 0.04 μB/f.u.), 1035.31 kA/m (5.14 ± 0.04 μB/f.u.) and 1044.34 kA/m (5.18 ± 0.04 μB/f.u.) at 5 K and 965.00 kA/m (4.79 ± 0.04 μB/f.u.), 967.75 kA/m (4.81 ± 0.04 μB/f.u.), and 1003.52 kA/m (4.97 ± 0.04 μB/f.u.) at 300 K, respectively. The soft ferromagnetic films possess coercivity of ∼ 15.92 kA/m (200 Oe) with a high effective anisotropy constant of ∼ 105 J/m3. Thermo-magnetization measurements yielded high Curie temperatures of 995 K, 1005 K, and 1123 K for films of thicknesses 320 nm, 780 nm, and 1400 nm, respectively. Tailoring the thickness from 320 to 1400 nm could be achieved by merely varying the electrodeposition time without appreciable departure from chemical stoichiometry or compromise in crystalline order or magnetic properties. This establishes a methodology to prepare high quality L21 ordered Co2FeSn films with a few hundred nanometers thickness by electrodeposition. Electrodeposited Co2FeSn films with high magnetic moment, high Keff value, and high Curie temperature are potential candidates for fabricating nanomagnetic devices.
•This work suggests approaches to control devitrification of amorphous soft ferromagnetic systems without non-magnetic alloying additions.•The Fe79Si11B10 melt-spun ribbon and water-quenched ...microwire follow different devitrification routes, depending on specific rapid solidification conditions.•The Fe79Si11B10 ribbon exhibits a ∼70% higher activation energy for primary devitrification relative to the microwire.•The ribbon crystallizes via a continuous nucleation process that partly relies on pre-existing surface nuclei, with interface-controlled growth.•The quenched microwire devitrifies solely from pre-existing nuclei, with diffusion-controlled growth.
Efficient electric machines require soft magnetic materials with superior properties, motivating research on the processing-structure-response correlation in Fe-based metallic glass systems. Here, significant differences in the primary devitrification process and the resulting microstructure of amorphous metallic Fe79Si11B10 alloys synthesized into two different forms by different rapid solidification methods are confirmed. Melt-spun ribbons and water-quenched microwires were investigated with calorimetric, structural, and magnetic probes. It is found that the primary devitrification process of the ribbons occurs at a higher temperature (by 80 K) with a faster exothermic heat release relative to that of the quenched microwires, despite their common chemical composition and fully devitrified structural state. Analysis of the primary devitrification reveals that the ribbons exhibit a ∼70% higher effective activation energy and a ∼110% larger value of Avrami exponent relative to those characterizing the microwires, indicating different devitrification routes taken by these two types of material. In specific, the ribbons crystallize via a continuous nucleation process that partly relies on pre-existing surface nuclei, with an interface-controlled growth mechanism. In contrast, the quenched microwires devitrify solely from pre-existing nuclei, with diffusion-controlled growth. These differences are attributed to unique quenched-in structures that are created by the specific rapid solidification conditions. These results suggest approaches to control the microstructure in FeSiB compositions without the need for non-magnetic alloying additions.
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