Magnetization measurements on zero field cooled (M_{ZFC}) and field cooled (M_{FC}) with temperature T were made on Fe_{0.7-x}M_xAl_{0.30} alloys (where M = Co or M = V). Compared to Co and V free alloy Fe_{0.7}Al_{0.30}, our results revealed that an addition of small amount of M = Co with 0≤ x≤0.10 shows linear decrease in the transition temperature T_f as x increases. Addition of small amount of M = V with 0≤ x≤0.1 shows gradual decrease in T_f with increasing x. The relative changes in T_f show that an addition of V atoms is of more significance than addition of Co atoms. There is a twofold decrease which could be attributed to the ferromagnetic nature of Co atoms and to the random fields.
The paper is aimed at the review of the charge and spin density perturbation on the iron nucleus in the bcc iron-based binary alloys containing as the impurity either 4d (Nb, Mo, Ru, Rh, Pd) or 5d (Os, Ir, Au) metals. Additionally, Ga was used as such impurity as well. Measurements were performed by means of the ^{57}Fe transmission Mössbauer spectroscopy at room temperature. Powder X-ray diffraction data for alloys investigated show linear dependence of the lattice constant versus impurity concentration. The Mössbauer data were treated assuming random distribution of the impurity over the iron sites and additive effect for the charge density perturbation, and additive in the algebraic sense effect for the corresponding spin density perturbation. Hence, the effect of impurity depends solely on the distance between impurity and the iron nucleus under above assumptions. It has been found that impurities being further away than a third or in some cases as the second neighbor do not contribute directly to the charge and spin perturbation. On the other hand, they have usually some minor effect on the average charge and spin density. Generally, the perturbation to either charge or spin density has some oscillatory character versus distance from the impurity. The phase and period of the charge oscillation is vastly different from the phase and period of the spin oscillation in the majority of cases. Substitution of the impurities with the increasing number of 4d or 5d electrons leads to the lowering of the electron density on the iron nucleus and causes decreased band spin density on this nucleus. Subsequent impurities donate more and more d-type electrons to the band, and the latter screen more and more effectively s-like electrons. Hence, the density of the s-like electrons on the iron nucleus diminishes. Impurities with 5d electrons have generally stronger effect on the charge and spin density perturbation than impurities with 4d electrons.
In the present study, the influence of Al and Ga admixture on the lattice parameters and the Curie point T_{C} of the La(Fe, Co, Si)_{13} compound was discussed. The measurements were carried out on ribbon samples of LaFe_{11.0}Co_{0.8}Si_{1.2}, LaFe_{11.0}Co_{0.8}(Si_{0.4}Al_{0.6})_{1.2} and LaFe_{11.0}Co_{0.8}Si_{1.1}Ga_{0.1} alloys. The samples were subjected to annealing in the inert gas atmosphere at 1323 K for 24 h. The change of lattice parameters a with admixture of Al and Ga was determined from the X-ray diffraction analysis. Furthermore, changes of the Curie point with the alloy composition were observed.
The aim of the present work was to study the isothermal compression and isobaric thermal expansion behaviour of ball-milled NiFe (81 wt.% of Ni) and NiFeMo (79 wt.% of Ni, 16 wt.% of Fe) alloy and follow its phase evolution when exposed to high pressure and temperature. In-situ pressure-temperature energy dispersive X-ray (EDXRD) diffraction experiments were performed at the MAX80 instrument (beamline F2.1). The compressibility of NiFe alloy at 400 °C was evaluated for pressure values of up to 3.5 GPa. The EDXRD spectra revealed the presence of cubic FeNi_{3} phase as determined from the shift of (111), (200) and (220) reflection lines in corresponding EDXRD spectra.
Employing the LMTO-ASA method we calculated the total energy variation of Fe_{3}Pt along the tetragonal distortion path connecting fcc and bcc structures for isotropic biaxial path and uniaxially strained path and compare the results with energies for the unstrained path.
In the present work the influence of Al and Ga on formation of La(Fe,Si)_{13}-type phase in magnetocaloric LaFe_{11.14}Co_{0.66}Si_{1.2-x}M_x (where x=0.1, 0.2, 0.3; M = Al, Ga) alloys subjected to annealing at 1323 K for 15 days was studied using the Mössbauer spectroscopy. For annealed samples, two crystalline phases were recognized: the dominant paramagnetic La(Fe,Si)_{13}-type phase, and minor fraction of ferromagnetic α -Fe(Co,Si). It was revealed that Al improved formation of 1:13 phase in contrast to Ga, which caused reduction of the ability of formation of the expected phase.
Application potential of the soft magnetic composites increases with improvement of their functional properties. In addition to the magnetic properties, the mechanical properties of these materials are essential. The aim of this work was to investigate mechanical properties and their dependence on morphology of the ferromagnetic particles. Model composite based on Somaloy® and Vitroperm® powder was prepared using conventional powder metallurgy. The DC magnetic properties of composites based on two types of ferromagnetic particles with different shapes and structures are discussed in the relation with mechanical properties.
In this study, we have investigated the microstructure and magnetic entropy change of annealed LaFe_{11.0}Co_{0.8}(Si_{0.4}Al_{0.6})_{1.2} alloy in a form of bulk samples and melt-spun ribbons. The bulk samples were annealed at 1323 K for 20 and 49 days and the maximum values of the magnetic entropy change | ΔS_M | obtained after the change of external magnetic field from 0 to 5 T reached 7.5 J kg^{-1} K^{-1} and 7.7 J kg^{-1} K^{-1}, respectively. For the melt-spun ribbon annealed at the same temperature for 1 h, the maximum value of | ΔS_M | reaches 4.5 J kg^{-1} K^{-1}. The temperature corresponding to the maximum entropy change increased from 292 K for bulk samples to 295 K for melt-spun ribbons. The lower values of the magnetic entropy change in the melt-spun LaFe_{11.0}Co_{0.8}(Si_{0.4}Al_{0.6})_{1.2} are attributed to the presence of higher volume fraction of the secondary bcc-Fe phase in the ribbon samples.
The aim of this work was to investigate the influence of microstructural features on the soft magnetic properties. The materials chosen for this work were two types of the Epstein strips of commercially produced non-oriented electrical steels by U.S. Steel Košice. The AC magnetic properties in 0.2-100 Hz frequency range were obtained by measurements of AC hysteresis loops by a fluxmeter based non-standard single sheet AC hysteresisgraph. The influence of the grain size and magnetic domains structure on the partial contributions (hysteresis, eddy current and anomalous) to the total losses is also discussed. The results of the frequency dependence of the total losses, measured by a single sheet loop tracer along the rolling direction and perpendicular to the rolling direction, show different contribution of partial components.
In the present work, the phase constitution and magnetic properties of the LaFe_{11.14}Co_{0.66}Si_{1.2-x}Ga_{x} (where x=0.1, 0.2, 0.3) alloys, were investigated. It was revealed that increase of Ga content in the alloy composition causes the rise of lattice parameter of the La(Fe,Si)_{13}-type phase, which causes increase of the Curie temperature. However, the increase of Ga addition leads to decrease of magnetocaloric effect.
This paper presents a new artificial neural network approach based on loss separation model to compute power loss on different types of electrical steels. The network was trained by a Levenberg-Marquardt algorithm. The results obtained by using the proposed model were compared with a commonly used conventional model. The comparison has shown that the neural network model is in good agreement with experimental data with respect to the conventional model.
The domain wall movement and magnetization rotations processes are separated experimentally in quasi-static magnetization process of a Finemet type ultrasoft magnetic material. The reversible domain rotations contribution is obtained from the integration of the reversible permeability, μ_{DR}, as a function of biasing DC field, measured with very small alternative field amplitude, less than 0.05H_c. The domain wall movement component is obtained by the integration of the permeability obtained by extraction of μ_{DR} from the differential permeability derived from one branch of the quasi-static major loop.
In the present work, Curie temperature, refrigeration capacity and cooling power of the LaFe_{11.0}Co_{0.8}(Si_{1-x}Al_{x})_{1.2} (where x=0, 0.6) alloys, are investigated. The value of Curie temperature was found to be 280 and 290 K for x=0 and 0.6, respectively. The determined values of cooling power (RCP) and refrigeration capacity (RC) differ only slightly for both investigated alloys. The maximum values of RCP and RC obtained under the change of external magnetic field from 0 to 5 T are 433 J/kg (for x=0) and 290 J/kg (for x=0.6), respectively.
Electronic and magnetic properties of body centered tetragonal YFe_{8}V_{4} carbon doped compounds were determined by tight-binding linear muffin-tin orbitals method assuming experimental values of lattice constants. Total, partial densities of states and magnetic moments for YFe_{8}V_{4} and its carbides for different positions of carbon within unit cell of parent compound were calculated and discussed. In spite of carbides' unit volume decrease enhancement of magnetization and Curie temperature were obtained. Results are in quantitative agreement with experimental data.
We report on ^{57}Fe-Mössbauer studies of the magnetic properties in ScFe_2 and Sc_{0.4}Ti_{0.6}Fe_2 performed as a function of pressure and temperature. Both systems crystallize in the C14-type Laves phase structure with two different Fe sites 6h and 2a. The ferromagnetic properties of ScFe_2 (T_C=540 K at ambient pressure) change around 30 GPa to antiferromagnetic order of the 6h sites with non-magnetic 2a sites. The ordering temperature is lowered to T_N=300 K at 51 GPa. This pressure-dependent behaviour of ScFe_2 resembles that observed within the Sc_{1-x}Ti_xFe_2 series as a function of x. In ferromagnetic Sc_{0.4}Ti_{0.6}Fe_2 we observe, as a function of temperature and of pressure, an abrupt high-moment to low-moment transition of the Fe band moments of the 6h sites, accompanied by a rearrangement of the spin directions. In both systems the decrease in the Fe moments is accompanied by a strong increase in the volume coefficient of the isomer shift, originating from a reduced s-electron shielding capability of the d-electrons in the low-moment state.
The electronic properties of Fe_{3}Al were determined experimentally, with the use of the Mossbauer spectroscopy, and theoretically. The band structure of the compounds was investigated applying the self-consistent tight-binding linear muffin tin orbital method. The calculated Fermi contact term of hyperfine fields and the isomer shifts are in good agreement with the values resulting from analysis of experimental data. The different kinds of electron transfer estimated on the base of the proposed "additive model" are also strongly supported by calculations.
Magnetic properties of amorphous alloys of the type Fe_{80-x}TM_{x}B_{20} (0 ≤ x ≤ 20 at.%, TM = Ni, Co, Mn, Cr, V, Ti) are presented and analyzed. The basis of our research work was the Mössbauer measurements, magnetic saturation measurements, derivative thermo-magnetogravimetry and differential thermal analysis measurements. The magnetic moments are discussed in terms of Friedel's virtual-bound-state model for light TM impurities in strong ferromagnets. Some conclusions about the electronic structure are presented.
In the present work, phase constitution and thermomagnetic properties of LaFe_{11.14}Co_{0.66}Si_{1.2-x}Al_{x} (where x = 0.1, 0.2, 0.3) alloys were investigated. Ingot samples were obtained by arc-melting under the low pressure of Ar atmosphere. Subsequently samples were annealed at 1323 K for 15 days. X-ray diffraction of all samples revealed coexistence of two crystalline phases dominant La(Fe,Si)_{13}-type and minor bcc α -Fe. Furthermore, the magnetic measurements at various temperatures allowed to study the Curie temperature, magnetic entropy changes and relative cooling power.
The aim of this paper was to study the influence of partial substitution of Fe by Mn in the LaFe_{11.2-x}Mn_{x}Co_{0.7}Si_{1.1} (where x=0.1, 0.2 and 0.3) alloys. Measurements revealed that a systematic increase of Mn in the alloy composition resulted in a decrease of the Curie temperature, which correlated with a decrease of the lattice parameter of the La(Fe,Si)₁₃- type phase. For samples corresponding to Mn content x=0.1 and 0.2 a decrease of magnetic entropy change was observed. However in the case of the sample with x=0.3 an increase of magnetic entropy change was detected.
The main goal of the present work was to study the critical behavior in the as-quenched Gd₇₅Ge₁₅Si₅Ce₅ (wt%) in the vicinity of the critical temperature T_{C}. The second order phase transition from a ferro- to a paramagnetic state was confirmed by the positive slope of the Arrott plots and analysis of temperature evolution of the Landau coefficients. The critical exponents have been revealed using the Kouvel-Fisher method and yield β=0.376±0.006, γ=1.032±0.006 and δ=3.835±0.008. The Curie temperature for the as-quenched Gd₇₅Ge₁₅Si₅Ce₅ equals 275.7±0.1 K.
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