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Magnetic refrigeration is a fascinating superior choice technology as compared with traditional refrigeration that relies on a unique property of particular materials, known as the magnetocaloric effect (MCE). This paper provides a thorough understanding of different magnetic refrigeration technologies using a variety of models to evaluate the coefficient of performance (COP) and specific cooling capacity outputs. Accordingly, magnetic refrigeration models are divided into four categories: rotating, reciprocating, C-shaped magnetic refrigeration, and active magnetic regenerator. The working principles of these models were described, and their outputs were extracted and compared. Furthermore, the influence of the magnetocaloric effect, the magnetization area, and the thermodynamic processes and cycles on the efficiency of magnetic refrigeration was investigated and discussed to achieve a maximum cooling capacity. The classes of magnetocaloric magnetic materials were summarized from previous studies and their potential magnetic characteristics are emphasized. The essential characteristics of magnetic refrigeration systems are highlighted to determine the significant advantages, difficulties, drawbacks, and feasibility analyses of these systems. Moreover, a cost analysis was provided in order to judge the feasibility of these systems for commercial use.

Ni-Mn based heusler alloy with Ni 50-x Fe x Mn 30 Sn 20-y In y where 1<=x<=4; 2<=y<=8 are studied for their structural as well as mechanical characteristics using various testing facility such as field emission scanning electron microscope, energy dispersion spectrometry, differential scanning calorimetry and Vickers hardness equipment. From the general understanding the materials are to display a transformation of austenite-martensite. The materials are seen to be showing this transformation in and around near room temperature. The optical and FESEM imaging of the specimen show that during annealing heating to high temperature to longer time, the diffusion kinetics are activated at faster rate so that the dendritically structure is annihilated to develop well distributed grain structure. The coarser dendrites seems to be broken and fine grain, well dispersed phases are formed. X-ray diffraction confirms the peak split and martensitic transformation in the system of alloys. DSC results confirm the martensitic transformation around room temperature.

The magnetocaloric effect (MCE) provides a promising foundation for the development of solid-state refrigeration technologies that could replace conventional gas compression-based cooling systems. Current research efforts primarily focus on identifying cost-effective magnetic materials that exhibit large MCEs under low magnetic fields across broad temperature ranges, thereby enhancing cooling efficiency. However, practical implementation of magnetic refrigeration requires more than bulk materials; real-world devices demand efficient thermal management and compact, scalable architectures, often achieved through laminate designs or miniaturized geometries. Magnetocaloric materials with reduced dimensionality, such as ribbons, thin films, microwires, and nanostructures, offer distinct advantages, including improved heat exchange, mechanical flexibility, and integration potential. Despite these benefits, a comprehensive understanding of how size, geometry, interfacial effects, strain, and surface phenomena influence the MCE remains limited. This review aims to address these knowledge gaps and provide guidance for the rational design and engineering of magnetocaloric materials tailored for high-performance, energy-efficient magnetic refrigeration systems.

It is a meaningful and challenging work for structural and synthetic chemists to isolate nano-sized high-nuclearity cluster-molecules. In this work, two largest hetero-metallic nano-clusters Gd 158 Co 38 were obtained via the “multi-anions-template” method. Different from the reported giant hollow-nano-clusters, the Ln 158 core in Gd 158 Co 38 (the protein-sized nano-clusters, ca. 4.3 nm × 3.6 nm × 3.5 nm) has the highest Ln nuclear number, which is integrated by twelve halide ions (with the form of icosahedron) as key templates, while Co ions (as 3d metals) are located in its periphery. This emergence indicates a novel structure form of non-open Ln-containing high-nuclearity clusters, and affords a consummate pattern to analyse and assemble the complex cluster-molecules. In addition, Gd 158 Co 38 @Cl 12 breaks the record magnetic entropy change of 3d–4f clusters with −Δ S m max = 46.95 J kg −1 K −1 at 7.0 T, 2.0 K.

Permanent magnets remain the primary source of magnetic field in magnetic refrigerators and thermomagnetic motors, generally being evaluated by the Λ cool parameter, which is applicable to a magnetic field source used in a magnetic refrigeration system. The main objective of this work is to perform a parametric and comparative analysis of a C-shaped and double C-shaped permanent magnet based on a common parameter to any arrangement of magnets, namely the figure of merit M ∗ . The analysis was conducted through computational modeling and simulation with COMSOL Multiphysics® software. Different soft magnetic materials were used in the simulations and the best-performing material was used in the magnetic circuit of the C-shaped permanent magnet to evaluate the magnetic force acting on a set of gadolinium plates. It was observed that the soft magnetic material has a significant impact on M ∗ . No significant impact on M ∗ was observed regarding to the number of gaps as long as more magnetized blocks are employed in the arrangement. Consequently, a greater gap accompanied by a lower magnetic flux density has the potential to result in an increased magnetostatic force density. Graphical Abstract

Here, we study the temporal evolution of the magnetic field-driven paramagnetic to ferromagnetic transition in the La(Fe,Mn,Si)13 material family. Three compositions are chosen that show varying strengths of the first-order character of the transition, as determined by the relative magnitude of their magnetic hysteresis and temperature separation between the zero-field transition temperature Tc and the temperature Tcrit, where the transition becomes continuous. Systematic variations in the fixed field, isothermal rate of relaxation are observed as a function of temperature and as a function of the degree of first-order character. The relaxation rate is reduced in more weakly first-order compositions and is also reduced as the temperature is increased towards Tcrit. At temperatures above Tcrit, the metastability of the transition vanishes along with its associated temporal dynamics. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

In this work, we will study magnetism and the magnetocaloric effect in amorphous ferromagnets formed by the series G d 100 - x N i x , where x = 29 , 32, 35 and 37. To calculate the magnetocaloric potential and magnetizations as a function of temperature and applied magnetic field, we will use the mean-field theory with the Handrich approximation to deal with the lack of structural order in amorphous systems. We seek to understand how the replacement of Gd by Ni influences the magnetocaloric properties of the binary alloys formed. The present study is important for the possible practical applications of the magnetocaloric effect and for understanding the microscopic mechanisms involved in the magnetic phase transitions of amorphous systems.

In this study, the compounds of La 2-x Na x NiMnO 6 ( x  =  0.0, 0.1, 0.2, 0.3, 0.5 , and 1.0 ) double perovskite manganites have been produced by employing the sol-gel method to investigate their magnetocaloric effect. From X-Ray Diffraction analysis, all compounds crystallized in rhombohedral structure form with the R 3 ¯ c space group confirmed using the Rietveld refinement technique. The compounds show a magnetic phase transition from ferromagnetic to paramagnetic according to the temperature-dependent magnetization measurement. The phase transition temperatures sharply increased with Na doping ( x  =  0.1 ) to 277.8 K which can be considered as under room temperature level and then slowly decreased with further Na concentration to 262.3 K. Using an external magnetic field-dependent magnetization measurements, the isothermal magnetization curves were obtained, and these curves used to find the magnetic entropy change values, which give info about compounds’ characteristics of magnetic cooling performance. Under 5 T magnetic field change, the maximum magnetic entropy change value increased 10 times with a small amount of Na doping ( x  =  0.1 ), and compounds’ values changed from 0.21 to 1.29 Jkg −1 K −1 for x  =  0.0 to 1.0 compounds, respectively. Arrott plots were graphed by using isothermal magnetization curves to demonstrate all the compounds have a 2 nd order magnetic phase transition which supports that these compounds can be candidates as magnetic refrigerants. Graphical Abstract Highlights The magnetocaloric properties of La 2-x Na x NiMnO 6 (0.0 ≤ x ≤ 1.0) double perovskite manganite system have been reported. The second-order magnetic phase transition which means reversible magnetic cooling cycles that upgrade the usability of the magnetic coolant materials has been achieved for all samples in La 2-x Na x NiMnO 6 (0.0 ≤ x ≤ 1.0) double perovskite manganite system. Na substitution resulted in an increase in the Curie temperature for all compounds. The structural properties and relationship with the magnetocaloric effect of La 2-x Na x NiMnO 6 (0.0 ≤ x ≤ 1.0) double perovskite manganite system have been explained. The morphological properties of the La 2-x Na x NiMnO 6 (0.0 ≤ x ≤ 1.0) double perovskite manganite system have been characterized.

The Gd 3 Co 10 Al 87 thin film was investigated since it contains a higher atomic rate of aluminum, an inexpensive, recyclable, and abundant material. A thermionic vacuum arc system deposited Gd 3 Co 10 Al 87 nanostructured thin film, and its surface and magnetic properties were analyzed. Mean grain dimension was measured as 30 nm and 50 nm, with the grain homogeneously distributed according to field emission scanning electron microscopy analyses. The film thickness was measured as 220 nm in cross-section field emission scanning electron microscopy. According to the X-ray diffraction analyses, Gd 2 O 3 and CoO crystal phases were detected. In temperature dependence of the magnetization measurements at 50Oe and 100Oe, double-Curie temperature behaviors were detected approximately at 90 K and 226 K. Refrigeration performance via thermodynamically analyzing an Ericsson refrigeration cycle was studied by taking the Curie temperatures as the cold reservoir temperatures and the hot reservoir temperatures varying 10 K, 15 K, and 20 K higher than Curie temperatures. At the Curie ranges of 90 K and 226 K, COPs of 4.86 and 7.2 were obtained, respectively, at hot reservoir temperatures of 10 K higher than Curie temperature. The Carnot efficiencies for low and high-temperature cycles were 17–52% and 17% and 32%, respectively, declining as the temperature span increases. The suggested cycles show the material’s potential to be utilized in a wide range of applications. Double-Curie approximation is a novel approach capable of opening a new gate for the broad range of magnetocaloric materials due to metal oxide phases.

Magnetocaloric hydrogen liquefaction could be a ‘game-changer’ for liquid hydrogen industry. Although heavy rare-earth based magnetocaloric materials show strong magnetocaloric effects in the temperature range required by hydrogen liquefaction (77–20 K), the high resource criticality of the heavy rare-earth elements is a major obstacle for upscaling this emerging liquefaction technology. In contrast, the higher abundances of the light rare-earth elements make their alloys highly appealing for magnetocaloric hydrogen liquefaction. Via a mean-field approach, it is demonstrated that tuning the Curie temperature ( T C ) of an idealized light rare-earth based magnetocaloric material towards lower cryogenic temperatures leads to larger maximum magnetic and adiabatic temperature changes (Δ S T and Δ T ad ). Especially in the vicinity of the condensation point of hydrogen (20 K), Δ S T and Δ T ad of the optimized light rare-earth based material are predicted to show significantly large values. Following the mean-field approach and taking the chemical and physical similarities of the light rare-earth elements into consideration, a method of designing light rare-earth intermetallic compounds for hydrogen liquefaction is used: tuning T C of a rare-earth alloy to approach 20 K by mixing light rare-earth elements with different de Gennes factors. By mixing Nd and Pr in Laves phase (Nd, Pr)Al 2 , and Pr and Ce in Laves phase (Pr, Ce)Al 2 , a fully light rare-earth intermetallic series with large magnetocaloric effects covering the temperature range required by hydrogen liquefaction is developed, demonstrating a competitive maximum effect compared to the heavy rare-earth compound DyAl 2 .