Academic literature on the topic 'Magnetocaloric effect, phase transition, magnetic refrigeration'
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Journal articles on the topic "Magnetocaloric effect, phase transition, magnetic refrigeration"
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Albertini, Franca, Massimo Solzi, Antonio Paoluzi, and Lara Righi. "Magnetocaloric Properties and Magnetic Anisotropy by Tailoring Phase Transitions in NiMnGa Alloys." Materials Science Forum 583 (May 2008): 169–96. http://dx.doi.org/10.4028/www.scientific.net/msf.583.169.
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The giant magnetocaloric properties of NiMnGa alloys can be enhanced by suitable composition changes that make structural and magnetic transition temperatures to coincide. In this paper we report results on critical temperatures, magnetic anisotropy, and magnetocaloric effect in Ni- and Mn-rich alloys as a function of composition. A phenomenological phase diagram, useful for the identification by thermomagnetic analysis of magnetic and structural transitions in the vicinity of their coincidence, is proposed. Particular emphasis is given to the discussion of giant magnetocaloric effect of those alloys showing a first order magnetostructural transition, the method of its determination, and the potentialities for applications in the field of magnetic refrigeration.
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Wang, Gao Feng, Zeng Ru Zhao, Xiao Bin Zhang, and Xue Feng Zhang. "First-Order Phase Transition and Magnetocaloric Effect of MnFeP0.63Ge0.12Si0.25 Compound." Advanced Materials Research 1053 (October 2014): 37–40. http://dx.doi.org/10.4028/www.scientific.net/amr.1053.37.
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In this paper, the magnetic phase transition and magnetocaloric effect have been investigated in the Fe2P-type MnFeP0.63Ge0.12Si0.25compound. The X-ray diffraction patterns measured at different temperatures indicate that the crystal structure remains and the lattice parameters change sharply near the transition temperature when a phase transition takes place. The isofield magnetization curves on heating and cooling and the Arrott plots reveal that the nature of the transition is first order. The characteristic of giant magnetocaloric effect results from the field-induced first-order metamagnetic phase transition, which makes the compound having potential applications in magnetic refrigeration.
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Liu, Quanyi, Zhaojun Mo, Huicai Xie, Qi Fu, Jun Shen, and Jinliang Zhao. "Magnetic properties and cryogenic magnetocaloric effect in monoclinic RE8.66(BO3)2(B2O5)O8 (RE = Er, Tm) compounds." Journal of Applied Physics 133, no. 1 (January 7, 2023): 013902. http://dx.doi.org/10.1063/5.0129082.
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Researchers in cryogenic magnetic refrigeration have never stopped pursuing magnetic refrigerants with lower ordering temperatures and larger magnetocaloric effects. Rare earth borates have been found to be potential cryogenic magnetocaloric materials due to their low phase transition temperatures and considerable magnetic entropy changes. Here, two rare earth borates RE8.66(BO3)2(B2O5)O8 ( RE = Er, Tm) were successfully fabricated, and the crystallographic and magnetic parameters as well as cryogenic magnetocaloric effects were systematically evaluated. The compounds are deemed to crystalize in a monoclinic structure belonging to space group C2/m. They are both second-order phase transition materials without any long-range order above 2 K. These monoclinic rare earth borates, especially for Er8.66(BO3)2(B2O5)O8, show more considerable low-field magnetocaloric effects than rare earth orthoborates. For Δ H = 1 and 2 T, the values of −Δ[Formula: see text] are 5.1 and 11.2 J/(kg K) for Er8.66(BO3)2(B2O5)O8, 3.0 and 5.3 J/(kg K) for Tm8.66(BO3)2(B2O5)O8, respectively. Therefore, they are regarded as potential candidates for cryogenic magnetic refrigeration.
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Gao, Li, Ying Feng, Shaohui Hu, and Xiangyang Xin. "Magnetostructural Transition and Magnetocaloric Effect with Negligible Magnetic Hysteresis in MnCoGe1.02−xGax Alloys." Metals 12, no. 7 (July 5, 2022): 1143. http://dx.doi.org/10.3390/met12071143.
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The behavior of magnetostructural transition and the magnetocaloric effect in the MnCoGe1.02−xGax (x = 0, 0.02, 0.04, 0.06) alloys are investigated in this study. The addition of Ga changes the crystal structure of MnCoGe1.02−xGax alloys at room temperature and reduces the phase transition temperatures with increasing Ga content. The coupling of magnetostructural transition and negligible magnetic hysteresis is observed in the Mn-Co-Ge-Ga alloy. At 305 K, under the action of a 5 T magnetic field, the MnCoGeGa0.02 alloy exhibits 23.47 J/kg∙K magnetic entropy change, and its refrigeration capacity reaches 387 J/kg. The large magnetic entropy change near room temperature and the high refrigeration capacity in the Mn-Co-Ge-Ga alloy make it a promising new type of refrigeration material.
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Pecharsky, Vitalij K., Jun Cui, and Duane D. Johnson. "(Magneto)caloric refrigeration: is there light at the end of the tunnel?" Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2074 (August 13, 2016): 20150305. http://dx.doi.org/10.1098/rsta.2015.0305.
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Caloric cooling and heat pumping rely on reversible thermal effects triggered in solids by magnetic, electric or stress fields. In the recent past, there have been several successful demonstrations of using first-order phase transition materials in laboratory cooling devices based on both the giant magnetocaloric and elastocaloric effects. All such materials exhibit non-equilibrium behaviours when driven through phase transformations by corresponding fields. Common wisdom is that non-equilibrium states should be avoided; yet, as we show using a model material exhibiting a giant magnetocaloric effect, non-equilibrium phase-separated states offer a unique opportunity to achieve uncommonly large caloric effects by very small perturbations of the driving field(s). This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.
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Мирошкина, О. Н., В. В. Соколовский, М. А. Загребин, С. В. Таскаев, and В. Д. Бучельников. "Теоретический подход к исследованию магнитных и магнитокалорических свойств сплавов Гейслера Ni-Mn-Ga." Физика твердого тела 62, no. 5 (2020): 697. http://dx.doi.org/10.21883/ftt.2020.05.49232.22m.
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The study of the magnetic and magnetocaloric properties of Ni2+xMn1-xGa (x = 0.16, 0.18 and 0.3) Heusler alloys are presented. The research was performed using a model based on the Malygin theory of smeared phase transitions, Bean–Rodbell theory of first-order phase transitions, and mean-field theory. The temperature dependences of deformation, magnetization, and isothermal entropy change are studied. It is shown that the largest change in magnetic entropy is observed in the Ni2.18Mn0.82Ga alloy, in which the martensitic transition is accompanied by a change in magnetic ordering. The smallest change in entropy is demonstrated by the Ni2.3Mn0.7Ga alloy, in which magnetocaloric the effect is observed in the martensitic phase upon a change in magnetic ordering. However, the refrigeration capacity of this alloy is twice as much as for the other considered compositions.
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Song, Zhao, Zongbin Li, Bo Yang, Haile Yan, Claude Esling, Xiang Zhao, and Liang Zuo. "Large Low-Field Reversible Magnetocaloric Effect in Itinerant-Electron Hf1−xTaxFe2 Alloys." Materials 14, no. 18 (September 11, 2021): 5233. http://dx.doi.org/10.3390/ma14185233.
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First-order isostructural magnetoelastic transition with large magnetization difference and controllable thermal hysteresis are highly desirable in the development of high-performance magnetocaloric materials used for energy-efficient and environmental-friendly magnetic refrigeration. Here, we demonstrate large magnetocaloric effect covering the temperature range from 325 K to 245 K in Laves phase Hf1−xTaxFe2 (x = 0.13, 0.14, 0.15, 0.16) alloys undergoing the magnetoelastic transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state on decreasing the temperature. It is shown that with the increase of Ta content, the nature of AFM to FM transition is gradually changed from second-order to first-order. Based on the direct measurements, large reversible adiabatic temperature change (ΔTad) values of 2.7 K and 3.4 K have been achieved under a low magnetic field change of 1.5 T in the Hf0.85Ta0.15Fe2 and Hf0.84Ta0.16Fe2 alloys with the first-order magnetoelastic transition, respectively. Such remarkable magnetocaloric response is attributed to the rather low thermal hysteresis upon the transition as these two alloys are close to intermediate composition point of second-order transition converting to first-order transition.
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Sechovský, Vladimír, Denys Vasylyev, and Jan Prokleška. "Magnetocaloric and Thermal Properties of Ho(Co1–xSix)2 Compounds." Zeitschrift für Naturforschung B 62, no. 7 (July 1, 2007): 965–70. http://dx.doi.org/10.1515/znb-2007-0714.
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Abstract The specific heat and thermal conductivity of HoCo2 and Ho(Co0.95Si0.05)2 were measured as functions of temperature in several constant magnetic fields up to 8 T. From a specific-heat data analysis the isothermal entropy change and the magnetocaloric effect (MCE) have been evaluated in a wide temperature range for several values of the applied magnetic field. The considerable values of the magnetocaloric effect in the vicinity of the magnetic ordering transition are qualifying both compounds as suitable for magnetic refrigeration purposes. The magnetic phase transition temperature (TC) increases from 77 K for HoCo2 to 103 K for Ho(Co0.95Si0.05)2 while the large MCE in the vicinity of TC is maintained, which demonstrates ways of tuning the operating temperatures of the magnetic refrigerant.
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Jing, Chao, X. L. Wang, D. H. Yu, Y. J. Yang, B. J. Kang, S. X. Cao, J. C. Zhang, Z. Li, J. Zhu, and B. Lu. "Magnetic Phase Transitions and Magnetocaloric Properties of Gd5Si0.4In3.6 Compound." Applied Mechanics and Materials 320 (May 2013): 67–71. http://dx.doi.org/10.4028/www.scientific.net/amm.320.67.
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The magnetic phase transitions and magnetocaloric properties of Gd5Si0.4In3.6 compound have been investigated. Magnetothermal measurements performed at different conditions reveal that the sample undergoes two magnetic phase transitions. One is a second-order transition from paramagnetic to ferromagnetic state at about 197 K, the other is a first-order transition when the temperature is reduced to 75 K. The magnetocaloric effect around Curie temperature (TC) was calculated in terms of isothermal magnetic entropy change by using Maxwells equation,which remains over a quite wide temperature span of 70 K between the temperature region from160 to 240 K, and thus makes this material attractive for magnetic refrigerator applications.
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Qiao, Kaiming, Yuhang Liang, Shulan Zuo, Cheng Zhang, Ziyuan Yu, Yi Long, Fengxia Hu, Baogen Shen, and Hu Zhang. "Regulation of Magnetocaloric Effect in Ni40Co10Mn40Sn10 Alloys by Using a Homemade Uniaxial Strain Pressure Cell." Materials 15, no. 12 (June 18, 2022): 4331. http://dx.doi.org/10.3390/ma15124331.
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In this study, a homemade uniaxial strain pressure cell was designed to be directly used in the standard magnetometers whereby the magnetic properties of samples subjected to a uniaxial strain and magnetic field were characterized. Its feasibility has been demonstrated by the uniaxial strain control of the phase transition and magnetocaloric effect in Ni40Co10Mn40Sn10 (NCMS) alloys. With the assistance of a uniaxial strain of ~0.5%, the cooling temperature span of NCMS alloys is broadened by 2 K, and the refrigeration capacity under a 3 T magnetic field change increases from 246 to 277 J/kg. This research provides not only direct experimental assistance for the tuning of phase transition by the uniaxial strain but also possibilities for studying the coupled caloric effect in first-order phase transition materials under a combined uniaxial strain and magnetic field by the thermodynamic analysis.
Dissertations / Theses on the topic "Magnetocaloric effect, phase transition, magnetic refrigeration"
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Quetz, Abdiel. "EXPLORATION OF NEW MAGNETOCALORIC AND MULTIFUNCTIONAL MAGNETIC MATERIALS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1378.
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The magnetic properties of NiMnGe1−xAlx, Ni50Mn35(In1−xBx)15, Ni50Mn35In14.5B0.5 (Bulk, As-Solidified and Annealed melt-spun ribbon) and RE-Infuse Carbon Nanotubes, have been studied by x-ray diffraction, differential scanning calorimetry (DSC), and magnetization measurements. Partial substitution of Al for Ge in NiMnGe1−xAlx results in a first-order magnetostructural transition (MST) from a hexagonal ferromagnetic to an orthorhombic antiferromagnetic phase at 186 K (for x = 0.09). A large magnetic entropy change of ∆SM = -17.6 J/kg K for ∆H = 5 T was observed in the vicinity of TM = 186 K for x = 0.09. This value is comparable to those of well-known giant magnetocaloric materials, such as Gd5Si2Ge2, MnFeP0.45As0.55, and Ni50Mn37Sn13. The values of the latent heat (L = 6.6 J/g) and corresponding total entropy changes (∆ST = 35 J/kg K) have been evaluated for the MST using DSC measurements. Large negative values of ∆SM of -5.8 and -4.8 J/kg K for ∆H = 5 T and up to 9T in the vicinity of TC were observed for x = 0.09 and 0.085, respectively. The impact of B substitution in Ni50Mn35In15-xBx Heusler alloys on the structural, magnetic, transport, and parameters of the magnetocaloric effect (MCE) has been studied by means of room-temperature X-ray diffraction and thermomagnetic measurements (in magnetic fields (H) up to 5 T, and in the temperature interval 5-400 K ). Direct adiabatic temperature change (ΔTAD) measurements have been carried out for an applied magnetic field change of 1.8 T. The transition temperatures (T-x) phase diagram has been constructed for H = 0.005 T. The MCE parameters were found to be comparable to those observed in other MCE materials such as Ni50Mn34.8In14.2B and Ni50Mn35In14X (X=In, Al, and Ge) Heusler alloys. The maximum absolute value of ΔTAD = 2.5 K was observed at the magnetostructural transition for Ni50Mn35In14.5B0.5. The structural phase transition temperatures, phase structure, and parameters of the magnetocaloric effect (MCE) of Ni50Mn35In14.5B0.5 as Bulk, As-Solidified and Annealed melt-spun ribbon has been studied by means of room-temperature X-ray diffraction and thermomagnetic measurements (in magnetic fields (oH) up to 5 T, and in the temperature interval 5–400 K). Magnetic and structural transitions in Ni50Mn35In14.5B0.5 as ribbons were found to coincide in Ni50Mn35In14.5B0.5 bulk sample, leading to a large magnetocaloric effects associated with the first-order magnetostructural phase transition. In comparison to the bulk Ni50Mn35In14.5B0.5 alloys, both the martensitic transition temperature (TM) and Curie temperature (TC) shifted to lower temperatures. Magnetic measurements revealed that the ribbons undergo a structure transformation similar to the bulk material at the martensitic transformation. The temperature of the transformation depends strongly on lattice parameters of the ribbons. MST shows a weak broad magnetic transition at TCM∼ 160 K, while the Curie temperature of AST TCA is ∼ 297 K. The MCE parameters were found to be comparable to those observed in other MCE materials such as Ni50Mn34.8In14.2B and Ni50Mn35In14X (X = In, Al, and Ge) Heusler alloys. These results suggest the possibility to control the martensitic transition in Ni50Mn35In14.5B0.5 through rapid solidification process. A comparison of magnetic properties and magnetocaloric effects in Ni50Mn35In14.5B0.5 alloys as Bulk, As-Solidified and Annealed ribbons is discussed. Carbon nanotube (CNT)/metal-cluster-based composites are envisioned as new materials that possess unique electronic properties which may be utilized in a variety of future applications. Super paramagnetic behavior was reported for CNTs with Gd ions introduced into the CNT openings by internal loading with an aqueous GdCl3 chemical process. In the current work, the magnetic properties of the CNT/Gd composites were obtained by the joining and annealing of Gd metal and CNTs at 850 °C for 48 h. Energy dispersive X-ray analysis shows the presence of Gd intermingled with the CNT walls with maximum and average Gd concentrations of about 20% and 4% (by weight), respectively. The Gd clusters have a non-uniform distribution and are mostly concentrated at the ends of the CNTs. A ferromagnetic-type transition at TC ∼ 320 K, accompanied by jump like change in magnetization and temperature hysteresis typical for the temperature induced first order phase transitions has been observed by magnetization measurements. It was found that Gd infused into the CNTs by the annealing results in a first order paramagnetic-ferromagnetic transition at TC = 320 K.
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BENNATI, CECILIA. "Physical behaviour and properties at the first order phase transition of magnetocaloric materials." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2652204.
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This Ph.D. project was mainly devoted to the study of the connection between magnetocaloric properties and first order phase transitions in ferromagnetic materials based on the La(Fe,Si)13 compound. The magneto caloric effect (MCE) and its application in magnetic cooling cycles rely on the reversible magnetization and demagnetization of a magnetic material by an external magnetic field, resulting in a temperature change that is maximal at temperatures close to a magnetic phase transition. The possibility to improve the performance of the active refrigerator materials, depends on many factors: the need of a Curie temperature close to ambient temperature, a low magnetic and thermal hysteresis and a high magnetic entropy variation for magnetic fields below two Tesla.
The latter requisite can be found in first order magnetic phase transitions that, unfortunately, are accompanied by intrinsic thermo-magnetic hysteresis. This drawback for magneto cooling cycles, motivates the present study on the phase transitions dynamics. On the other hand, the investigation of magneto-thermal phenomena in magnetic materials is of great importance also for solving fundamental problems of magnetism and solid state physics, for example, it is recognized that the properties of interest of such functional materials are intimately linked to the detailed micro structure, however, the nature of this link itself is not understood very often.
In this Ph.D. project, thermo-magnetic phase transitions in La(Fe,Si)13 compounds were investigated through the comparison of various experimental techniques within a collaboration between the applied superconductivity group of Politecnico of Torino and the electromagnetism division of INRiM (National Institute of Metrological Research). To achieve a proper physical understanding of the connection between thermo-magnetic hysteresis at the microscopic level and the microstructure, a magneto optical method was applied to samples of La-F-Si-13 with cobalt substitutions, so to allow the dynamical visualisation of the phase boundaries motion in a first order phase transition. These type of experiments have been compared with low rate calorimetry data and, from the experimental work, it has been found that the presence of avalanches is a characteristic feature of these alloys and it is related to their thermal hysteresis. The
difference between first and second order phase transition dynamics were highlighted thanks to the employment of different techniques, which also favoured the separation of the general aspects of hysteresis, common to all irreversible processes, from features more strictly dependent on specific microstructural properties. For the aim of this Ph.D., other techniques were also used to observe temperature induced magnetic phase transitions in functional magnetic materials. Among them an in-temperature ferromagnetic resonance method
was implemented for the study of the magnetization dynamics in canted spin structures.
The present research activity has been partially related to the European Project DRREAM [1] (a collaborative research project funded by the EC under the Seventh Framework Program 2013-2015), whose goal is to reduce the use of rare earth elements in the life cycle of technologies that use magnetic phase change materials, in particular magnetic refrigerators.
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Aryal, Anil. "EXPLORATION OF NOVEL MAGNETOCALORIC MATERIALS FOR APPLICATIONS IN MAGNETIC COOLING TECHNOLOGY." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1813.
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The effect of doping on the crystal structure, magnetic, magnetocaloric and transport properties of MnM′Ge (M′ = Ni, Co) intermetallic compounds and NiMnX (X = Sn, In) Heusler alloys have been studied by room temperature X-ray diffraction (XRD), differential scanning calorimetry (DSC), and magnetization measurements. The studied magnetic systems include Ni1-xCrxMnGe1.05 (0 ≤ x ≤ 0.120), Mn1-xAlxCoGe (0 ≤ x ≤ 0.05), MnCo1-xZrxGe (0.01 ≤ x ≤ 0.04), Mn1-xAgxCoGe (0.01 ≤ x ≤ 0.10), Ni50-xRxMn35Sn15 (x = 0, 1 and R = La, Pr, Sm), Ni43-xRxMn46Sn11 (x = 0, 1 and R = Pr, Gd, Ho, Er), and Ni50Mn35In15-xBix (0 ≤ x ≤ 1.5).A temperature induced first-order structural transition characterized by a change in crystal structure from high temperature austenite phase (AP) with Ni2In-type Hexagonal structure to low temperature martensite phase (MP) with TiNiSi-type orthorhombic structure was observed at T = TM (martensitic transition temperature) in some of the MnM′Ge-based compounds. The partial substitution of doping elements such as Cr, Al, Zr, and Ag resulted in a decrease in TM and at certain concentration, TM was found to decrease below / coincide with the ferromagnetic transition temperature (TC) of AP. Therefore, such system show a first-order magnetostructural transition (MST).In Ni1-xCrxMnGe1.05, a MST from antiferromagnetic (AFM) orthorhombic to ferromagnetic (FM) hexagonal phase was observed for 0.105 ≤ x ≤ 0.120. Both direct and inverse MCE were observed in this compound. The peak values of the magnetic entropy change (ΔSMpeak ) in the vicinity of TC for ΔH = 5T were found to be 4.5 J/kg K, 5.6 J/Kg K, and 5.1 J/Kg K for x = 0.105, 0.115, and 0.120 respectively. A magnetic field-induced transition from an AFM to a FM state in the martensite structure was observed in annealed Ni0.895Cr0.105MnGe1.05 melt-spun ribbons, which led to a coupled MST from a FM martensite to a PM austenite phase with a large change in magnetization. As a result of the field-induced MST, a large ΔSMpeak value of 16.1 J kg-1 K-1 (which is about a four times larger than the bulk) and Refrigeration capacity (RC-1) =144 J kg-1 at μ0∆H = 5 T was found. It was also found that the ribbon samples showed excellent magnetic reversibility that is important for application. MCE parameters, adiabatic temperature change (∆Tad) and |〖∆S〗_M |, with maximum value of ~ 2.6 K (µoH = 10 T) and 4.4 J kg-1 K-1(µo∆H = 5 T), respectively, were observed in the vicinity of TC. The ∆Tad (T) curves obtained for µoΔH = 10 T and magnetization isotherms were found to be completely reversible, which indicates the reversibility of the MCE in this system. A large temperature span (of about 61 K) and a non-saturating behavior of ∆Tad were observed at magnetic fields up to 10 T. The adiabatic temperature change was found to be a linear function of (µoH)2/3 near TC in accordance with Landau’s theory of phase transitions.In MnCoGe compounds doped with Al, Zr, and Ag, a tunable MST from the paramagnetic hexagonal to ferromagnetic orthorhombic phase was observed. The maximum ΔSM values of about 18, 7.2, and 22 J kg-1 K-1for ∆H = 5T at TM was observed for Al, Zr, and Ag doped compounds, respectively. The corresponding maximum value of RC was found to be (303, 266, and 308) JKg-1.The new compounds containing low concentration of rare earth (R) metals: Ni50-xRxMn35Sn15, Ni43-xRxMn46Sn11, with R = La, Pr, Sm, Gd, Ho, Er and Ni50Mn35In15-xBix were synthesized. The compounds crystallized in the cubic L21 austenite phase (AP) or a mixture of AP and low temperature martensitic phase (MP) at room temperature. For Ni50-xRxMn35Sn15 and Ni43-xRxMn46Sn11 alloys, TM shifted towards higher temperature with rare-earth doping, thus stabilizing the MP at higher temperature. A maximum shift in TM by ~ 60-62 K relative to the parent compound (TM = 190-195 K) was observed for the Ni49LaMn35Sn15 and Ni42PrMn46Sn11. TM shifted towards lower temperature if Bi is placed in In position in Ni50Mn35In15-xBix. A maximum shift of ~ 36 K was detected for x = 1.5. Abnormal shifts in TC and TM to higher temperatures were observed at high field for Bi concentration ≥ 0.5.The ground state magnetization decreased with the rare-earth doping and increasing Bi content. The compounds exhibit both inverse and normal magnetocaloric effects. Large values of ∆SM = 12 (Ni49PrMn35Sn15), 32 Jkg-1K-1(Ni42PrMn46Sn11), 28 Jkg-1K-1 (Ni42GdMn46Sn11), 25 Jkg-1K-1 (Ni42HoMn46Sn11), 40 J/kg K (Ni50Mn35In15) and 34 J/kg K (Ni50Mn35In15-xBix, x = 0.25) were found at TM for ∆H = 5T that can be tuned in a wide temperature range. RC values ranging from 267-336 Jkg-1 at TC, 182 -250 Jkg-1 at TM and 144-165 Jkg-1 at TC were found with ∆H = 5T for Ni50-xRxMn35Sn15, Ni43-xRxMn46Sn11, and Ni50Mn35In15-xBix, respectively. Significant magnetoresistance (MR) values of -30%, -20 % and -30% were observed in Ni49LaMn35Sn15, Ni42GdMn46Sn11, and Ni50Mn35In14.5Bi0.5 compounds, respectively, at TM and ∆H = 5T. A large exchange bias effect with HEB ~ 1.1 kOe at 10 K was observed for the Ni42PrMn46Sn11 compound in its MP. Thus, the pronounced multifunctional properties such as shape memory effects, MCE, EB, and MR make these new systems promising for the ongoing development of magnetocaloric and multifunctional technologies.
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Phejar, Mathieu. "Étude de nouveaux matériaux de type La(Fe1-xSix)13 pour la réfrigération magnétique à température ambiante." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00601081.
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La première partie des travaux réalisés a été dédiée à l' élaboration de composés LaFe13-xSix (1,3 ¡U x ¡U 2,2) par broyage à haute énergie. Il a fallu déterminer les conditions de synthèse et de recuit optimales pour l'obtention d'échantillons monophasés. Leur homogénéité a été analysée par diffraction des rayons X et microsonde électronique. Les résultats ont montré qu'une microstructure plus fine favorise la formation de la phase désirée : un recuit de 30 min (au lieu de 30 jours pour les massifs) à 1373K suffit à l'obtention d'un composé quasi-monophasé. D'après les mesures magnétiques effectuées, les composés synthétisés par broyage mécanique ont des proprié¦tés magnétiques et magnétocaloriques similaires aux massifs. Ils présentent une transition métamagnétique des électrons itinérants induite par le champ ou la température. Leur température de Curie augmente avec le Si, variant de 200K à 235K pour x = 1,4 à 2,0 alors que leur variation d'entropie magnétique diminue de 20 J/kg K à 4 J/kg K sous une variation de champ de 0-2 T. La deuxième partie de l'étude a consisté à améliorer les propriétés magnétocaloriques des intermétalliques par l'insertion d'atomes interstitiels (H, C). Les mesures magnétiques ont montré une nette augmentation de la température de transition (jusqu'à Tamb.) par effet magnétovolumique tout en conservant un effet magnétocalorique important. Les analyses par diffraction des neutrons en température effectuées sur les composés deutérés ont permis de suivre l'évolution des données cristallographiques et des moments magnétiques par Fe. Il ressort de cette étude que ces composés présentent un grand intérêt dans la recherche de futurs matériaux magnétocaloriques pour la réfrigération magnétique à température ambiante. Dans le cadre de l'exploration de nouveaux systèmes, les propriétés magnétocaloriques des composés Y1-xRxFe2D4,2 (R = Er, Tb) ont également été étudiés en couplant les études magnétiques avec des mesures de diffraction des neutrons
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Bauer, Christopher. "Magnetocaloric Effect in Thin Films and Heterostructures." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3003.
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The goals of this work are the optimization of the magnetocaloric effect in Gadolinium thin film structures. We approach this issue from two directions, that of process optimization and of interface effects. Past results showed Gd2O3 in our Gadolinium thin films, and the presence of such oxide seemed to grow with the temperature at which the film was grown or annealed. Comparison of samples grown without chamber gettering to those that were gettered show differences in their structural and magnetic properties, and we conclude that gettering is an effective step in enhancing the quality of Gd thin film samples.
Early work with Gd/W heterostructures showed a diminished magnetization of the interfacial gadolinium, which reduces the magnetocaloric response as magnetic entropy is proportional to m2/3. It is known that Fe interfaces can boost the Gd moments per atom to above that seen in bulk. As such, we fabricated a series of Fe/Gd heterostructures to study the effects on the structural and magnetic properties of Gd thin films. The use of Fe as a base layer shows increased high frequency oscillations in X-ray reflectivity measurements, indicating sharp interfaces between Gd and Fe. The magnetocaloric measurements produce a magnetic entropy curve with a novel tail extending leftward, making this an improved material over Gd for applications around 240K. All the same, vector magnetometry is needed to ensure that such tail is not due to rotations within the plane and is a direction for further study.
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Das, Ranjit Chandra. "The Effect of Stoichiometric Variation on the Magnetocaloric Properties of Selected Mn-Fe-Ni-Si-Al Intermetallic Compounds." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626959102771612.
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Mboukam, Jean Jules. "Magnetocaloric effect and critical behaviour near the magnetic phase transition temperature in rare-earth compounds." University of the Western Cape, 2018. http://hdl.handle.net/11394/6218.
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Magister Scientiae - MSc (Physics)Rare-earth intermetallic compounds continue to draw considerable attention, due to their fundamental importance in understanding physical properties and potential applications based on a variety of phenomena. The focus of this project is to employ two family of rare-earth intermetallic compounds: RE2Pt2In (RE = Pr, Nd) and RE8Pd24Ga (RE = Gd, Tb, Dy) ternary intermetallic systems as a model candidate to uncover the underlying ground state properties that result in a strong coupling between the conduction electron and the 4f-electron of the rare-earth ions.
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Akintunde, Babajide O. "A study on the effect of Fe-Ni variation on the magnetocaloric properties of Mn0.5Fe0.5+xNi1-xSi0.94Al0.06 and Mn0.5Fe0.5-xNi1+xSi0.94Al0.06 systems." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami16267284137581.
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Caron, Luana. "Da síntese e do efeito magnetocalórico de compostos derivados do Fe2P, Mn2Sb e MnAs." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277089.
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Orientadores: Sergio Gama, Ekkes BruckTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nesta tese de doutoramento são apresentados os resultados do estudo das propriedades magnéticas, magnetocalóricas e estruturais de algumas séries de compostos que são de interesse para aplicação em refrigeração magnética baseada no efeito magnetocalórico. Os métodos de preparação da série MnFe P1-xAsx são estudados de forma a otimizar o tempo de preparação e as propriedades magnétocalóricas. Uma nova série de compostos baseada na anterior, a MnFeGe1-xSix foi descoberta, apresentando transições de fase magnética de segunda ordem e uma variação linear dos parâmetros de rede em função da concentração de Si no intervalo 0 £ x £ 0,7. Também foi descoberto, associado à uma transição magnética de segunda ordem, o efeito magnetocalórico no composto MnFeSn cujo TC situa-se em torno da temperatura ambiente. Foi feito o estudo do efeito magnetocalórico dos compostos baseados no Mn2Sb com o Mn parcialmente substituído por Cr, V, Co e Cu e o Sb substituído por Ge. Nestes compostos uma transição do tipo Exchange Inversion é induzida pelas substituições, transformando o estado ferrimagnético em antiferromagnético em baixa temperatura, dando origem ao chamado efeito magnetocalórico inverso. Ainda foi desenvolvido um modelo fenomenológico para descrever tal transição e o efeito magnetocalórico associado. Por fim é reportado o efeito magnetocalórico colossal nos compostos M n1-xCux As, devido ao qual os métodos de medida magnéticos do efeito magnetocalórico são revistos. A partir dos resultados em diferentes procedimentos de medida, é proposta uma forma de medir o efeito em materiais altamente histeréticos que não leva a resultados espúrios
Abstract: On this PhD thesis some results on the magnetic, magnetocaloric and structural properties of some series of compounds suitable for applications on magnetocaloric effect-based refrigeration are presented. The FeMnP1-xAsx series preparation methods are studied in order to optimize their magnetocaloric properties as well as to shorten its preparation time. A new series of compounds based on the previous one was studied, the MnFeGe1-xSix. These compounds present a second-order magnetic phase transition and a linear change in lattice parameters with Si content on the 0 £ x £ 0.7 range. Also associated with a second-order phase transition, the magnetocaloric effect on FeMnSn was discovered around room-temperature. A careful study of Mn2Sb-based compounds with Mn partially substituted by Cr, V, Co and Cu and Sb by Ge was performed. On these compounds an Exchange Inversion transition is induced by substitutions taking the material from the ferrimagnetic to the antiferromagnetic state with decreasing temperature, giving rise to the so-called inverse magnetocaloric effect. A phenomenological theoretical model was also developed to describe such transitions and their associated magnetocaloric effect. Finally we report on the colossal magnetocaloric effect on Cu-substituted MnAs compounds. Due to this compound¿s unusual behavior, the magnetic measurements of the magnetocaloric effect are reviewed. Based on the results of different measurement procedures a new method of measurement for highly hysteretic compounds is proposed which leads to non spurious results
Doutorado
Materiais Magneticos e Propriedades Magneticas
Doutor em Ciências
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Cavaignac, André Luís de Oliveira. "Estudo comparativo dos cristais L-alanina, L-treonina e taurina com variação de temperaturas por espectroscopia Raman." Universidade Federal do Maranhão, 2015. http://tedebc.ufma.br:8080/jspui/handle/tede/1339.
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Structural, magnetic and magnetocaloric properties of the RMn2Si2 compounds (R = Tm, Dy and Tb) were studied. X ray diffraction analysis and structure Rietveld refinement shows that the samples crystallize with the desired tetragonal I4/mmm structural phase. Magnetization measurements shows second order magnetic phase transition from paramagnetic (PM) to ferromagnetic (FM) state for TmMn2Si2 compound around T = 5.2 K. On the other hand, DyMn2Si2 and TbMn2Si2 compounds present multiple phase transitions below 100 K. DyMn2Si2 present four magnetic phase transitions while TbMn2Si2 present two magnetic phase transition. Both compounds present first order FM phase transitions originated from ordering of rare earth sub-lattice. In addition, DSC measurements indicated that DyMn2Si2 and TbMn2Si2 compounds present high temperature phase transition at T~ 425 K and 444 K associated to the AFM coupling in the Mn sub-lattice. Magnetic hysteresis loop was used to characterize exchange bias effect in the DyMn2Si2 observed for magnetic fields higher than 35 kOe in which was associated to interactions between AFM and FM magnetic domain present in this compound. The largest magnetocaloric effect (MCE) was observed for TmMn2Si2 compound, when compared with other studied compound. The maximum values of entropy variation change −∆𝑆𝑀 𝑚á𝑥 and the Relative Cooling Power (RCP) found for TmMn2Si2 were, respectively, 18.5 J/kg.K and 247.5 J/kg for a magnetic field change (H) of 50 kOe. Significant values of −∆𝑆𝑀 𝑚á𝑥 (~8.2 J/kg.K and ~9.7 J/kg.K@50 kOe, respectively) and RCP (124.6 J/kg and 233 J/kg@50 kOe, respectively) as well as successive magnetic phase transitions were observed for DyMn2Si2 and TbMn2Si2 compounds. Also these two compound exhibits a table like EMC presenting a wide working window for practical applications. The results obtained for compounds motivate the preparation of a composite sample with the following concentrations 10% de TmMn2Si2, 15% de HoCoSi, 35% de DyMn2Si2 e 40% de TbMn2Si2, aiming further increase in the temperature range of maximum EMC. The maximum entropy change variation obtained for the composite sample was ~4.6 J/kg.K over a temperature range of ~80𝐾. Our results show that the compounds RMn2Si2 present important characteristics for application in magnetic refrigeration for cryogenic temperatures. Besides, it is possible to get a larger working region, when these compounds are associated forming a composite material.
Neste trabalho foi realizado um estudo das propriedades estruturais, magnéticas e magnetocalóricas dos compostos da série RMn2Si2 (R = Tm, Dy e Tb). A análise estrutural por difração de raios X e refinamento dos difratogramas pelo método de Rietveld mostraram que as amostras cristalizam na fase tetragonal grupo espacial I4/mmm. Com a medida de magnetização foi possível observar a transição de fase magnética de segunda ordem do estado paramagnético (PM) para ferromagnético (FM) para o composto TmMn2Si2 em torno de 5,2 K. Enquanto que para os compostos DyMn2Si2 e TbMn2Si2 observou-se a presença de transições múltiplas abaixo de 100 K. O DyMn2Si2 apresentou quatro transições de fase magnética enquanto que TbMn2Si2 apresentou duas. Em ambos os compostos, as transições ferromagnéticas atribuídas ao ordenamento da sub-rede da terra rara são de primeira ordem. Medidas DSC indicaram que DyMn2Si2 e TbMn2Si2 apresentam uma transição de fase em T~ 425 K e 444 K, respectivamente, ambas relacionadas ao acoplamento antiferromagnético na sub-rede do Mn. Com as medidas do loop de histerese magnética foi possível caracterizar o efeito de Exchange Bias (EB) para o DyMn2Si2, em campos magnéticos superiores a 35 kOe, o qual foi atribuído a interações entre os domínios AFM e FM presentes no material. A caracterização das propriedades magnetocalóricas do composto TmMn2Si2 mostrou uma variação de entropia magnética (-∆SM) mais intensa quando comparada aos outros compostos deste estudo. Os valores máximos obtidos para a variação isotérmica da entropia (−∆𝑆𝑀 𝑚á𝑥 ) e para o poder de resfriamento relativo (RCP) foram, respectivamente 18,5 J/kg.K e 247,5 J/kg, para ∆𝐻 = 50 kOe. Já os compostos DyMn2Si2 e TbMn2Si2 mostraram valores significativos de −∆𝑆𝑀 𝑚á𝑥 (~8,2 J/kg.K e ~9,7 J/kg.K@50 kOe, respectivamente) e RCP (124,6 J/kg e 233,6 J/kg@50 kOe, respectivamente) além de duas transições de fase magnética sucessivas, o que resultou em um EMC com comportamento do tipo table-like, caracterizado por uma ampla janela de trabalho com máximo EMC. Estes resultados motivaram a preparação de um compósito com as seguintes concentrações 10% de TmMn2Si2, 15% de HoCoSi, 35% de DyMn2Si2 e 40% de TbMn2Si2, visando ampliar ainda mais o intervalo de máximo EMC. A variação máxima de entropia obtida para o compósito foi da ordem de 4,6 J/kg.K num intervalo de temperatura de ~80𝐾. Os resultados obtidos sugerem que os compostos desta série apresentam características importantes para aplicação na refrigeração magnética em temperaturas criogênicas. Além disso, quando estes estão associados na forma de um compósito é possível obter uma grande ampliação na região de trabalho.
Book chapters on the topic "Magnetocaloric effect, phase transition, magnetic refrigeration"
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Hsini, Mohamed, and Souhir Bouzidi. "Magnetocaloric Properties in Gd3Ni2 and Gd3CoNi Systems." In Latest Research on Energy Recovery. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.102065.
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Intermetallic Gd3Ni2 and Gd3CoNi undergo second-order ferromagnetic paramagnetic phase transition at the Curie temperature, TC. They exhibit a large magnetocaloric effect (MCE). This MCE is manifested with a high entropic peak of 8 and 8.3 J.Kg−1 K−1, at the vicinity TC under 5 T magnetic applied field for Gd3Ni2 and Gd3CoNi, respectively. With their boosted MCE and large refrigerant capacity, Gd3Ni2 and Gd3CoNi compounds can be a candidate as a magnetocaloric refrigerator which is still one of the current research projects recommended by the low energy consumption and low environmental impact of these devices. Based on the Landau theory, Gibb’s free energy leads to determine temperature-dependent parameters which correspond to the electron condensation energy and magnetoelastic coupling and the magnetic entropy change which is a very crucial parameter to evaluate the MCE of a given magnetic system.
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Jemmali, Mosbah, and Lotfi Bessais. "Effect of M Substitution on Structural, Magnetic and Magnetocaloric Properties of R2Fe17-x Mx (R = Gd, Nd; M = Co, Cu) Solid Solutions." In Magnetic Skyrmions. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96299.
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The structure, magnetic and magnetocaloric properties of Nd2Fe17−xCox (x = 0; 1; 2; 3, 4) and Gd2Fe17-xCux (x = 0, 0.5, 1 and 1.5) solid solutions have been studied. For this purpose, these samples were prepared by arc melting and subsequent annealing at 1073 K for a 7 days. Structural analysis by Rietveld method on X-ray diffraction (XRD) have determined that these alloys crystallize in the rhombohedral Th2Zn17-type structure (Space group R¯3 m) and the substitution of iron by nickel and copper leads to a decrease in the unit cell volume. The Curie temperature (TC) of the prepared samples depends on the nickel and copper content. Based on the Arrott plot, these analyses show that Nd2Fe17-xCox exhibits a second-order ferromagnetic to paramagnetic phase transition around the Curie temperature. These curves were also used to determine the magnetic entropy change ∆SMax and the relative cooling power. For an applied field of 1.5 T, ∆SMax increase from 3.35 J/kg. K for x = 0 to 5.83 J/kg. K for x = 2. In addition the RCP increases monotonously. This is due to an important temperature range for the magnetic phase transition, contributing to a large ∆SMax shape. Gd2Fe17-xCux solid solution has a reduction of the ferromagnetic phase transition temperature from 475 K (for x = 0) to 460 K (for x = 1.5) is due to the substitution of the magnetic element (Fe) by non-magnetic atoms (Cu). The magnetocaloric effect was determined in the vicinity of the Curie temperature TC. By increasing the Cu content, an increase in the values of magnetic entropy (∆SMax) in a low applied field is observed.
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Hsini, Mohamed, and Sadok Zemni. "Modeling the Magnetocaloric Effect of Nd0.67Ba0.33Mn0.98 Fe0.02O3 by the Mean Field Theory." In Magnetometers - Fundamentals and Applications of Magnetism. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.82559.
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In this paper, we have exploited the mean field theory combined with the Bean-Rodbell model to justify the magnetocaloric effect (MCE) in Nd0.67Ba0.33Mn0.98Fe0.02O3 sample. The simulation of some magnetic properties has been investigated. Modeling magnetization curves have been successfully achieved using this model. The second-order ferromagnetic-paramagnetic (FM-PM) phase transition of our system has been verified through the value of the parameter which controls the transition nature in the Bean-Rodbell model. Theoretical and experimental expressions, which have rated the magnetic entropy change ( − ∆ S M ) under various magnetic fields, have been derived. Theoretical ( − ∆ S M ) curves have been compared to the experimental ones.
Reports on the topic "Magnetocaloric effect, phase transition, magnetic refrigeration"
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Johra, Hicham. Performance overview of caloric heat pumps: magnetocaloric, elastocaloric, electrocaloric and barocaloric systems. Department of the Built Environment, Aalborg University, January 2022. http://dx.doi.org/10.54337/aau467469997.
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Heat pumps are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water production. Conventional heat pumps are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The heat pump market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional heat pumps can have a large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression heat pump technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining large attention. These caloric effects are characterized by a phase transition varying entropy in the material, resulting in a large adiabatic temperature change. This phase transition is induced by a variation of a specific external field applied to the solid refrigerant. Therefore, the magnetocaloric, elastocaloric, electrocaloric and barocaloric effects are adiabatic temperature changes in specific materials when varying the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. Heat pump cycle can be built from these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not a mature technology yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and domestic hot water production. This technical report (and the paper to which this report is supplementary materials) aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression heat pumps for building applications.