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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]

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]

It is well recognized that intermetallics based on rare-earth (R) and transition metals (T) display numerous interesting magnetic properties, leading to potential applications in different fields. The latest progress regarding magnetic properties and the magnetocaloric effect (MCE) in the nanostructured Pr 2 Co 7 compound, as well as its carbides and hydrides, is reviewed in this paper. Some of this progress reveals remarkable MCE performance, which makes it attractive in the field of magnetic refrigeration at high temperatures. With the purpose of understanding the magnetic and magnetocaloric characteristics of these compounds, the crystal structure, microstructure, and magnetism are also brought into focus. The Pr 2 Co 7 compound has interesting magnetic properties, such as a high Curie temperature T C and uniaxial magnetocrystalline anisotropy. It crystallizes in a hexagonal structure (2:7 H) of the Ce 2 Ni 7 type and is stable at relatively low temperatures (T a ≤ 1023 K), or it has a rhombohedral structure (2:7 R) of the Gd 2 Co 7 type and is stable at high temperatures (T a ≥ 1223 K). Studies of the magnetocaloric properties of the nanocrystalline Pr 2 Co 7 compound have shown the existence of a large reversible magnetic entropy change (Δ S M ) with a second-order magnetic transition. After its substitution, we showed that nanocrystalline Pr 2 Co 7 − x Fe x compounds that were annealed at T a = 973 K crystallized in the 2:7 H structure similarly to the parent compound. The extended X-ray absorption fine-structure (EXAFS) spectra adjustments showed that Fe atoms preferably occupy the 12k site for x ≤ 1. The study of the magnetic properties of nanocrystalline Pr 2 Co 7 − x Fe x compounds revealed an increase in T C of about 26% for x = 0.5, as well as an improvement in the coercivity, H c (12 kOe), and the (BH) max (9 MGOe) product. On the other hand, the insertion of C atoms into the Pr 2 Co 7 cell led to a marked improvement in the T C value of 21.6%. The best magnetic properties were found for the Pr 2 Co 7 C 0.25 compound annealed at 973 K, H c = 10.3 kOe, and (BH) max = 11.5 MGOe. We studied the microstructure, hydrogenation, and magnetic properties of nanocrystalline Pr 2 Co 7 H x hydrides. The crystal structure of the Pr 2 Co 7 compound transformed from a hexagonal (P63/mmc) into an orthorhombic (Pbcn) and monoclinic (C2/c) structure during hydrogenation. The absorption of H by the Pr 2 Co 7 compound led to an increase in the T C value from 600 K at x = 0 to 691 K at x = 3.75. The Pr 2 Co 7 H 0.25 hydride had optimal magnetic properties: H c = 6.1 KOe, (BH) max = 5.8 MGOe, and T C = 607 K. We tailored the mean field theory (MFT) and random magnetic anisotropy (RMA) methods to investigate the magnetic moments, exchange interactions, and magnetic anisotropy properties. The relationship between the microstructure and magnetic properties is discussed. The obtained results provide a fundamental reference for adapting the magnetic properties of the Pr 2 Co 7 , Pr 2 Co 6.5 Fe 0.5 , Pr 2 Co 7 C 0.25 , and Pr 2 Co 7 H 0.25 compounds for potential permanent nanomagnets, high-density magnetic recording, and magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]