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.
The aim of the present work was to study the phase transition in the LaFe_{11.14}Co_{0.66}Si_{1.1}M_{0.1} (where M = Al or Ga) alloys. Research was carried out using field dependences of magnetization measured at a wide temperature range. Positive slope of the Arrott plots showed that magnetic phase transition in both investigated samples was of second order nature. The temperature dependences of the Landau coefficients also revealed second order phase transition in both specimens. The analysis carried out using universal curve confirmed second nature of phase transition in both samples.
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.
The aim of present work was to study the influence of partial substitution of Co by Mn in the LaFe_{11.2}Co_{0.7}Si_{1.1} alloy on its structure and magnetic properties. The X-ray diffraction studies revealed coexistence of dominant pseudobinary fcc La(Fe,Si)_{13}-type phase with minor fraction of α-Fe. Moreover, the increase of Mn content causes decrease of the lattice parameter and the Curie temperature. The values of magnetic entropy change obtained for both investigated alloys are almost identical and close to 12 J/(kg K) under the change of external magnetic field ≈5 T. Investigations of magnetic phase transition confirmed its second order nature in the case of both specimens.
In the present work the microstructure and thermomagnetic properties of Fe₈₀Zr₇Cr₆Nb₂Cu₁B₄ ribbon in the as-quenched state and after the accumulative annealing in the temperature range 600-800 K for 10 min were studied using Mössbauer spectroscopy and vibrating sample magnetometry. The second order phase transition from ferro- to paramagnetic state is observed. The Curie temperature T_{C} defined as inflection point on the magnetization versus temperature curve recorded on zero-field cooled mode equals 262.5 K for the as-quenched material. With increasing the annealing temperature increase of T_{C} is observed. The maximum value of the magnetic entropy change (-ΔS) observed in the vicinity of the Curie point is equal to 0.85 J/(kg K) for the alloy in the as-quenched state. Moreover, for the samples annealed up to 750 K for 10 min the low intensity maximum at about 190 K related to the supplementary magnetic phase is observed. The presence of this phase was confirmed as additional component visible on hyperfine field distributions of Mössbauer spectra.
Fe-based amorphous alloys were characterized by X-ray diffraction, transmission Mössbauer spectroscopy and vibrating sample magnetometry. The studies were performed on (Fe_{0.75}B_{0.15}Si_{0.1})_{100-x}Zr_{x} (x=0, 1, 3) metallic glasses in the form of ribbons. The glassy samples were prepared by the "melt spinning" technique in argon protective atmosphere. The XRD patterns show the broad diffraction halo that is typical for amorphous Fe-based alloys. The Mössbauer spectroscopy allows to study the local environments of the Fe atoms in the glassy state, showing the changes in the amorphous structure due to the changing of Zr addition. From hysteresis loops obtained from vibrating sample magnetometry measurements, coercive force and saturation magnetization were determined versus different Zr content. The obtained magnetic properties allow to classify the studied amorphous alloys in as-cast state as soft magnetic materials.
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 presented work was to study influence of preparing conditions on phase constitution and magnetic properties of the RE-Fe-B nanocomposite magnets doped with Zr. X-ray studies carried out for samples obtained under lower pressure of Ar atmosphere (0.6×10⁵ Pa) revealed higher ability to formation of nanocrystalline structure. In case of higher pressure of Ar (0.8×10⁵ Pa) it was possible to obtain full amorphous ribbon during melt-spinning process. The best magnetic properties (means the higher values of coercivity field _{J}H_{c}, remanence J_{r} and maximum energy product (BH)_{max}) were measured for sample prepared with the lowest copper wheel speed 20 m/s and higher pressure of Ar (0.8×10⁵ Pa).
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.
In the present work the magnetic properties and phase constitution of (Nd₁₀Fe₆₇B₂₃)_{100-x}Nbₓ (where x = 1, 2, 4) alloys in the form of ribbons were investigated. The base alloys were prepared by arc-melting the high purity elements with pre-alloyed Fe-B under an Ar atmosphere. The ribbon samples were obtained by controlled atmosphere melt-spinning technique. In order to generate the nanocrystalline microstructure and hard magnetic properties, samples were annealed at various temperatures (from 923 K to 1023 K) for 5 min. The aim of the present work was to determine the influence of Nb admixture and annealing conditions on the phase constitution and magnetic properties.
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.
Soft magnetic composites are readily used in the design of electromagnetic converters and electrical machines. In the paper, the magnetic properties of "home-made" cores made of iron powder and suspense polyvinyl chloride are examined. Samples were prepared by hot pressing of a PVC/Fe powder mixture with a different ratio of constituent components. Phase composition was investigated using an X-ray diffractometer and the presence of α-Fe was detected. Measurements of magnetic permeability revealed its allometric decrease with an increase of PVC content in composite. For the description of magnetization curves the phenomenological Jiles-Atherton model is used. The results of simulations are in a qualitative agreement with experiment.
The aim of this paper was to study the phase constitution, magnetic properties and magnetization reversal processes in the rapidly solidified bulk (Pr,Dy)-(Fe,Co)-B alloys doped with Zr, Ti, Mn and Ni. The 3 mm outer diameter tubes samples of the Pr₈Dy₁Fe₆₀Co₇Ni_{(6x)}MnₓB₁₄Zr₁Ti₃ (where x = 0, 3, 6) alloys were produced by suction-casting technique. The admixture of Zr was introduced in order to improve their glass forming abilities while Dy was substituted to enhance the magnetocrystalline anisotropy of hard magnetic phase. The effect of Ni and Mn addition on the phase constitution and magnetic properties was studied in the presented work.
The ferromagnetic Fe-based amorphous alloys were studied due to properties for soft magnetic applications. Depending on different Nb addition, the formation of crystalline phases after annealing of amorphous Fe_{80-x}B₂₀Nb_{x} (x = 4,6,10) alloys was studied. The crystallization products as well as the phase structure were determined using the Mössbauer spectrometry combined with differential scanning calorimetry and magnetic measurements. The addition of Nb caused a shift of crystallization process towards higher temperatures and induced changes in coercive force and decreased the saturation magnetization. It was found that Nb addition changed the crystallization process from single crystallization for Fe₇₆B₂₀Nb₄ alloy to binary crystallization in the Fe₇₄B₂₀Nb₆ and Fe₇₀B₂₀Nb₁₀ glasses. The annealing process at the onset crystallization temperature induced complex phase formation including the α-Fe, Fe₃B, and Fe₂B phases for alloys x=4, 6.
Melt-spun ribbons were produced from the Pr₈Dy₁Fe₆₀Co₇Mn₆B₁₄Zr₁Ti₃ base alloy at the surface velocity of the cooper wheel of 30 m/s. The studies showed amorphous structure of ribbons and their soft magnetic properties. X-ray diffraction was used to determine phase constitution of all obtained samples. Annealing of ribbons caused formation of nanocomposite structure, which was a result of coexistence of hard magnetic RE₂(Fe,Co)₁₄B and soft magnetic α-Fe phases. Basic magnetic properties such as: coercivity _{J}H_{c}, remanence J_{r} and maximum energy product (BH)_{max} were determined from the measured hysteresis loops. The microstructure of selected specimens was observed by transmission electron microscopy technique.
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.
In the present work the magnetic properties and phase constitution of (Nd_{10}Fe_{67}B_{23})_{100-x}Nb_{x} (where x=1, 2, 3, 4) alloys in a form of ribbons were investigated. The ribbon samples were obtained by controlled atmosphere melt-spinning technique. In order to generate the nanocrystalline microstructure, ribbons were annealed at various temperatures (from 923 K to 1023 K) for 5 min. Subsequent annealing resulted in an evolution of the phase constitution accompanied by a change of their magnetic properties. The X-ray diffraction studies show presence of hard magnetic Nd_{2}Fe_{14}B, paramagnetic Nd_{1+ε }Fe_{4}B_{4} and ferromagnetic metastable Nd_{2}Fe_{23}B_{3} phases. The best hard magnetic parameters were measure for annealed ribbons of the (Nd_{10}Fe_{67}B_{23})_{96}Nb_{4} alloy.
The aim of the present work was to study the influence of annealing conditions on magnetic properties and the phase constitution of rapidly solidified Fe_{64.32}Pr_{9.6}B_{22.08}W_{4} alloy ribbons. The base alloy was prepared by arc-melting of the high purity elements under an Ar atmosphere. Subsequently the ribbon samples were obtained by melt-spinning technique under low pressure of Ar. In order to develop nanocrystalline structure, the samples were annealed at 1003 K for 5, 10, 20 and 30 min. The room temperature magnetic properties were determined from hysteresis loops measured by VSM magnetometry in the external magnetic field up to 2 T. For comparison the influence of annealing temperature on magnetic properties was studied for the same alloy composition. The ribbons were annealed at temperatures from 929 K to 1023 K for 5 min. X-ray diffractometry was used to determine the phase composition of annealed ribbons. Heat treatment resulted in an evolution of the phase constitution, that caused changes in magnetic properties of the alloy.
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