Investigations of the Magnetic Phase Transition in the LaFe11.14Co0.66Si1.1M0.1LaFe_{11.14}Co_{0.66}Si_{1.1}M_{0.1} (Where M = Al or Ga) Alloys

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

Influence of Al and Ga on Formation of the La(Fe,Si)_{13}-Type Phase in the LaFe_{11.14}Co_{0.66}Si_{1.2-x}M_x (where x=0.1, 0.2, 0.3; M=Al, Ga) Alloys

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

Investigation of Critical Behavior in Gd₇₅Ge₁₅Si₅Ce₅ Alloy

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

Influence of Partial Substitution of Fe by Mn on the Thermomagnetic Properties of Magnetocaloric LaFe11.2Co0.7Si1.1LaFe_{11.2}Co_{0.7}Si_{1.1} Alloy

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

Structure and magnetic properties of Fe-B-Si-Zr metallic glasses

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

Measurements of Magnetocaloric Effect in LaFe11.14Co0.66Si1.2−xAlxLaFe_{11.14}Co_{0.66}Si_{1.2-x}Al_{x} (x=0.1, 0.2, 0.3) Alloys

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

Effect of Preparing Conditions on the Phase Constitution and Magnetic Properties of Nd-Pr-Fe-Zr-B Alloy Ribbons

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 $\text{}_{J}H_{c}$, 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)

Structural and magnetic properties of the as - cast Nd10Fe83Zr1B6 ribbons, studied by X-ray diffraction and Mössbauer spectroscopy

The Nd10Fe83Zr1B6 alloy ribbons, prepared by melt-spinning technique, have been investigated by X-ray diffraction (XRD) and Mossbauer spectroscopy. Magnetic properties were studied by Faraday balance and vibrating sample magnetometry (VSM). The ribbon samples were produced at various surface velocities of the copper wheel from 10 m/s to 20 m/s. The XRD and Mossbauer spectra analysis have shown that the ribbons consist of the soft magnetic alfa-Fe, hard magnetic Nd2Fe14B and disordered phases. The results showed that a uniform Nd2Fe14B/alfa-Fe nanocomposite structure with fine alfa-Fe grains can be obtained at an optimum velocity of the cooper roll of 20 m/s. The samples produced in these conditions had the best magnetic properties (mi0HC= 0.84 T, mi0MR = 1.05 T, mi0MS = 1.36 T, (BH)max = 160 kJ/m3) with strong exchange coupling between the hard magnetic Nd2Fe14B and soft magnetic mi-Fe phases. The amorphous phase existing between grains causes an increase in the remanence and remanence ratio

Measurements of Magnetocaloric Effect in LaFe 11.14

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

Phase constitution of an LaFe11.0Co0.8(Si0.4Al0.6)1.2 alloy investigated by Mössbauer spectroscopy

In the present work the phase constitution and magnetic ordering of the magnetocaloric LaFe11.0Co0.8(Si0.4Al0.6)1.2 alloy in the as-cast state and after annealing at 1323 K for 1 h (in case of ribbons) and 49 days (in case of bulk) were studied. For bulk and ribbon samples in as-cast state three crystalline phases were identified: dominant ferromagnetic alfa-Fe, minor ferromagnetic La(Fe,Co)Si and traces of paramagnetic La(Fe,Si)13 phase. Appropriate heat treatment resulted in the evolution of phase constitution of the alloy, where two crystalline phases were developed: the dominant paramagnetic La(Fe,Si)13 phase and a minor fraction of the ferromagnetic alfa-Fe for both bulk and ribbon samples