Search

In this study, we give a thorough evaluation of the structural, magnetic, and magnetocaloric properties in iron-rich PrFe 11 Ti intermetallic alloy with ThMn 12 -type structure using a combination of experimental and theoretical analysis. X-ray diffraction coupled with Rietveld refinement was used to characterize the structure, which revealed a unique tetragonal crystal structure with I 4 / m m m space group. The 8 i site was identified as the preferred site for the Ti atom. This finding was confirmed by various techniques, including XRD, DFT, and Mössbauer spectrometry. Magnetic properties were studied through intrinsic magnetic measurements and magnetocaloric effect analysis. Mössbauer spectroscopy was employed to probe the local magnetic environment and for further characterization of the material's magnetic properties. The experimental results were complemented by theoretical calculations based on density functional theory (DFT). A promising magnetocaloric effect is observed, with a significant maximum magnetic entropy ( − Δ S M max = 2.5 J·kg − 1 ·K − 1 ) and a relative cooling power about 70 J·kg − 1 under low magnetic field change μ 0 Δ H = 1.5 T. Overall, our results provide a deeper understanding of the structural and magnetic properties of the material under study and demonstrate the effectiveness of the combined experimental and theoretical approach in the investigation of complex materials. The insights gained from this study could have implications for the development of advanced magnetic materials with enhanced properties for potential magnetic applications. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study in the critical region around the Curie temperature to determine the universality class of the Sm 2 Ni 17 intermetallic compound. The magnetocaloric effect has been studied on the basis of experimental measurements of magnetization. Maxwell's relation and a phenomenological model are employed to find the change in magnetic entropy. The compound Sm 2 Ni 17 presents a variation in entropy with a moderate maximum and a wide range of operating temperatures. Numerous approaches have been used to explore the spontaneous magnetization behaviour and inverse of the susceptibility, including the modified Arrott technique, the Kouvel–Fisher approach, and the fitting of the critical isotherm. The scaling hypothesis has been used to confirm the validity and interdependence of the critical exponents associated with these phenomena. [ABSTRACT FROM AUTHOR]

Iron-based compounds with a ThMn12-type structure have the potential to bridge the gap between ferrites and high performance Nd2Fe14B magnets. From the point of view of possible applications, the main advantage is their composition, with about 10 wt.% less rare earth elements in comparison with the 2:14:1 phase. On the other hand, the main issue delaying the development of Fe-rich alloys with a ThMn12-type structure is their structural stability. Therefore, various synthesis methods and stabilizing elements have been proposed to stabilize the structure. In this work, the influence of increasing Nd substitution on the phase constitution of Zr0.4−xNdxCe0.6Fe10Si2 (0 ≤ x ≤ 0.3) alloys was analyzed. X-ray diffraction and 57Fe Mössbauer spectrometry were used as the main methods to derive the stability range and destabilization routes of the 1:12 structure. For the arc-melted samples, an increase in the lattice parameters of the ThMn12-type structure was observed with the simultaneous growth of bcc-(Fe,Si) content with increasing Nd substitution. After isothermal annealing, the ThMn12-type structure (and the coexisting bcc-(Fe,Si)) were stable over the whole composition range. While the formation of a 1:12 phase was totally suppressed in the as-cast state for x = 0.3, further heat treatment resulted in the growth of about 45% of the ThMn12-type phase. The results confirmed that the stability range of ThMn12-type structure in the Nd-containing alloys was well improved by other substitutions and the heat treatment, which in turn, is also needed to homogenize the ThMn12-type phase. After further characterization of the magnetic properties and optimization of microstructure, such hard/soft magnetic composites can show their potential by exploiting the exchange spring mechanism. [ABSTRACT FROM AUTHOR]

The effect of carbonation on the structure and the magnetic properties of polycrystalline YTi[Fe.sub.11-x] [Si.sub.x] (0 [less than or equal to] x [less than or equal to] 2) have been investigated by means of x-ray diffraction (XRD) at room temperature and magnetic measurements at low temperature. The alloys were prepared by typical induction melting and the carbonation was performed by solid-solid reaction. The cell volume of Th[Mn.sub.12] structure and the Curie temperature increase after carbonation, but decrease with Si content. The saturation magnetization and the magnetic moment were determined from parallel magnetic isotherms using the common law of approach to saturation. The experimental average magnetic moment per atom decreases with Si content. The comparison of experimental 3d-magnetic moment with the calculated values from the magnetic valence approximation (MVA) shows a strong ferromagnetism, induced by carbonation. The XRD patterns of magnetically oriented powder show an uniaxial anisotropy for Y[Fe.sub.11-x][Si.sub.x] TiC. The second and fourth order magnetocrystalline constants, [K.sub.1] and [K.sub.2] have been determined using an analytical interpretation, based on the statistical model, of perpendicular magnetization isotherms of the magnetically aligned powder samples. The magnetocrystalline constants and anisotropy field have been determined versus temperature and composition. Index Terms--Magnetic anisotropy, magnetic materials, magnetic measurements, yttrium compounds.

In this study, we investigate the crystal structure, magnetic, and magnetocaloric effect properties in the intermetallic compounds SmNi 3 − x Fe x using a phenomenological model based on Landau mean-field theory and Maxwell relation (conventional method). SmNi 3 − x Fe x compounds were prepared under high pure argon by arc melting. To minimize the amount of other possible impurity phases, the ingots were heat-treated at 1073 K for seven days. X-ray diffraction (XRD) under and without an applied magnetic field was used for the structural study. Rietveld analysis with FullProf computer code was used to analyze X-ray diffraction data. The magnetization against temperature was measured under several applied magnetic fields. After the partial substitutions of nickel atom with iron one, we notice an increase of cell parameters. In addition, Curie temperature value increases significantly with the increase of iron content. According to the Landau model, SmNi 3 − x Fe x compounds exhibit a second-order magnetic phase transition. The magnetic entropy change was determined with theoretical and experimental methods. Finally, a comparison between theoretical magnetic entropy change and the experimental show an agreement between the two methods. [ABSTRACT FROM AUTHOR]

LaFe13-xSix compounds exhibit a giant magnetocaloric effect and they are considered as a good magnetocaloric working substance for an environmentally friendly cooling technique. Nevertheless as the Curie temperature TC is around 200 K, it is necessary to tune TC near room temperature for magnetic refrigeration. In this work we present a review of the various methods of synthesis and shaping of the LaFe13-xSix type compounds as well as the influence of chemical substitution, light element insertion or combination of both on TC, magnetic entropy and adiabatic temperature variation ΔSM and ΔTad), and stability upon cycling. The advantages and drawbacks of each method of preparation and type of element substitution/insertion are discussed. The implementation of these NaZn13 type materials in active magnetic refrigerator is presented and their performances are compared to that of Gd in prototypes. [ABSTRACT FROM AUTHOR]