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Magnetic refrigeration technology based on the magnetocaloric effect (MCE) of magnetic substances has been considered a prominent, energy‐efficient, and environmentally benign cooling method. Exploring suitable magnetic substances is a prerequisite for practical applications. A family of rare‐earth‐free magnetocaloric materials called Mn30Fe20−xCuxAl50 alloys is identified room‐temperature refrigeration, which are derived from the well‐known MnAl‐based permanent magnets. As expected from experimental and theoretical investigations, all of the Mn30Fe20−xCuxAl50 alloys are crystallized in a stable cubic CsCl‐type crystal structure, revealing a single second‐order type magnetic phase transition (MPT) with tunable MPT temperature. They also exhibit a large reversible MCE and good magnetocaloric performances in a wide temperature range. Crucially, these Mn30Fe20−xCuxAl50 alloys represent a rare case of magnetic materials belonging to a large family that can be fabricated from low‐price, earth‐abundant, and non‐toxic elements. They could provide new choices for practical room‐temperature magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

In this paper, a detailed investigation with respect to the structural, cryogenic magnetic properties and magnetocaloric performances of RE 2 CuMnO 6 (RE = Gd, Dy, Ho and Er) double perovskite (DP) compounds has been performed. All the RE 2 CuMnO 6 compounds are confirmed to B -site disordered and crystallized in the GdFeO 3 -type structure (Pnma space group, N 62, oP20). The magnetic transition temperatures (T M) are found to be ~7.5 K for Gd 2 CuMnO 6 , ~12.1 K for Dy 2 CuMnO 6 , ~12.2 K for Ho 2 CuMnO 6 , and ~3.6 K for Er 2 CuMnO 6 , respectively. Moreover, for checking the magnetocaloric performances several vital parameters including -Δ S M max (peak value of magnetic entropy change, -Δ S M), TEC (3) (temperature averaged -Δ S M) and RCP (relative cooling powers) are evaluated to be 7.84, 7.73 J/kgK and 151.1 J/kg for Gd 2 CuMnO 6 , 5.69, 5.59 J/kgK and 180.9 J/kg for Dy 2 CuMnO 6 , 7.12, 7.05 J/kgK and 192.4 J/kg for Ho 2 CuMnO 6 , as well as 9.92, 9.60 J/kgK and 195.9 J/kg for Er 2 CuMnO 6 under the magnetic field change Δ H = 5 T, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ferromagnetic Al-Mn-Fe-Co-Cr high-entropy (HE) alloys were fabricated. • Structural, magnetic and magnetocaloric (MC) properties were reported. • Combined experimentally determined and theoretically analyzed was performed. • Excellent MC properties were achieved at room temperature. • These HE alloys have potential for room temperature magnetic refrigeration. In the present study, the structure, magnetic phase transition, and magnetocaloric performance of Al 20 Mn 20 Fe 20 Co 14.5+ x Cr 25.5- x (x = 0, 1, and 2), a series of typical rare-earth-free high-entropy (HE) alloys, were experimentally determined and theoretically analyzed based on first-principle calculation. Ferromagnetic behavior was established and their Curie temperature could be tuned in a wide temperature range, which correlated with Co content; specifically, it increased from 282.8 K for Co 14.5 Cr 25.5 to 345.8 K for Co 16.5 Cr 23.5. In addition, the electronic density of states and magnetic moments associated with each consistent element were analyzed in the HE alloys. Maximum magnetic entropy changes of 1.135, 1.150, and 1.096 J/kgK were obtained for an x of 0, 1, and 2 under a magnetic field change of 5 T. These values are comparable or superior to those of reported 3 d metal-based HE alloys. Furthermore, the experimental characterizations and theoretical predications agreed well, which provided an in-depth understanding of the rare-earth-free HE Al-Mn-Co-Fe-Cr alloy system, which is expected to be expanded to other systems in the future. [ABSTRACT FROM AUTHOR]

The Heusler type Ni–Mn- Z (Z = Ga, ln, Sn, or Sb) alloys with magneto-structural transformations (MSTs) have received widespread research interests due to the exhibition of multifunctional characters. To further understand MSTs and improve the magnetocaloric performance of these alloys, in this work, the Ti doped Ni 48 Cu 2 Mn 36 Sn 14-x Ti x (x = 0, 1, 2, 3) ribbons have been fabricated and systematically determined with regard to the structural, magnetic, and magnetocaloric properties by means of X-ray diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC), and magnetization measurements. All the ribbons are found to crystallize in the ordered cubic L2 1 austenite phases at room temperature and with the equiaxed austenite morphology. With the increasing Ti content, the average grain size and the MST temperature increase but the austenite Curie temperature (T A C) decrease gradually. Moreover, the thermal hysteresis and magnetic hysteresis loss are greatly reduced with the Ti doping. The value of average hysteresis loss (AHL) is reduced from 86 Jkg−1 for Ti0 to 25.5 Jkg−1 for Ti3 ribbon under 7 T. Additionally, enhanced magnetocaloric effect has been observed by Ti-doping. With the magnetic field change (ΔH) of 0–7 T, the largest value of magnetic entropy change reaches 15.4 Jkg−1K−1 (Ti2) among the Ni 48 Cu 2 Mn 36 Sn 14-x Ti x ribbons. The present work indicates that reasonable Ti doping could be a useful way to regulation the MSTs and improve the magnetocaloric performance of the Heusler type Ni–Mn–Sn-based alloys. • The Hesuler type Ni 48 Cu 2 Mn 36 Sn 14-x Ti x (x = 0, 1, 2, 3) ribbons are fabricated. • The structural, magnetic and magnetocaloric properties were investigated. • Ti doping could be a useful way to regulation the MSTs. • Enhanced magnetocaloric performances has been observed by Ti-doping. [ABSTRACT FROM AUTHOR]

The magnetic refrigeration (MR) technology by utilizing the magnetocaloric (MC) effects of magnetic solids have been realized to be a promising energy efficiency and environmentally friendly technology. Developing or discovering proper magnetic solids with promising MC performances is one of the most important tasks at present stage since a huge gap still exists between the requirement of practical MR application and the MC performances of the magnetic solids. Herein, we reported a combined theoretical and experimental investigation of the crystal structure together with the magnetic properties, magnetic phase transition (MPT) and MC performances in Gd 2 MgTiO 6 oxide. The Gd 2 MgTiO 6 is confirmed to crystalize in a B -site ordered monoclinic double perovskite (DP) crystal structure. A rather unstable antiferromagnetic (AFM) interaction with large magnetic moment and semi-conductor characteristic with the band gap of 2.977 eV have been confirmed in Gd 2 TiMgO 6 DP oxide at ground state. Giant reversible cryogenic MC effect together with excellent MC performances have been confirmed by a series of the figure of merits including the values of maximum magnetic entropy change (-Δ S M) and refrigerant capacity (RC), which are evaluated to be 46.21 J/kgK and 300.27 J/kg around 3.3 K with the magnetic change of 0–7 T, these values are much better than most of the recently reported famous cryogenic MC materials and the commercialized magnetic refrigerants gadolinium gallium garnet (GGG) as well. The observed excellent MC performances suggest that Gd 2 TiMgO 6 DP oxide is a promising candidate material for cryogenic MR applications. Graphical abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

The rare-earths (RE) based amorphous materials with large magnetocaloric (MC) effects and excellent glass forming ability (GFA) have been recognized as promising candidates for magnetic refrigeration (MR). In this work, the RE 60 Co 20 Al 20 (RE = Ho, Er, Tm) amorphous ribbons were successfully fabricated and systematically determined with respect to the GFA, magnetic properties and MC effects. A second order magnetic phase transition (MPT) from ferromagnetic to paramagnetic (FM to PM) without noticeable field or thermal hysteresis has been observed around the Curie temperatures, T C ~ 22.3 K for Ho 60 Co 20 Al 20 , ~ 10.3 K for Er 60 Co 20 Al 20 , and ~ 5.0 K for Tm 60 Co 20 Al 20 , respectively. The MC parameters including the maximum magnetic entropy change (| Δ S M max |), temperature-averaged entropy change with 3 K lift [ TEC (3 K)], and relative cooling powder/refrigerant capacity (RCP/RC) have been determined to check the MC performances, and the corresponding values are determined to be 14.16, 15.57 and 15.06 J/kgK, to be14.04, 15.38 and 14.78 J/kgK, and to be 625.0/478.7, 505.7/391.8 and 334.0/243.4 J/kg for Ho 60 Co 20 Al 20 , Er 60 Co 20 Al 20 and Tm 60 Co 20 Al 20 under the field change Δμ 0 H = 5 T, respectively. The present results indicate that RE 60 Co 20 Al 20 (RE = Ho, Er, Tm) amorphous ribbons are considerable for cryogenic MR application. • The RE 60 Co 20 Al 20 (RE = Ho, Er, Tm) amorphous ribbons are fabricated. • The glass forming ability in RE 60 Co 20 Al 20 amorphous ribbons was investigated. • Large magnetocaloric effect in RE 60 Co 20 Al 20 has been observed. • RE 60 Co 20 Al 20 ribbons are considerable for cryogenic magnetic refrigeration. [ABSTRACT FROM AUTHOR]

We herein provided a systematical determination of the structural and magnetic properties, especially of the magnetocaloric effect (MCE) and magnetocaloric performances of four rare-earth oxychlorides, i. e., the RE OCl (RE = Ho, Dy, Tb and Gd) compounds. The studied RE OCl compounds are all crystallized in the tetragonal matlockite structure (P 4/ nmm space group) and the RE , O, and Cl elements are with the RE 3+, O2−, and Cl− valence states, respectively. The DyOCl, TbOCl and GdOCl compounds reveal an antiferromagnetic transition at around approximate 9.5, 3.7 and 4.8 K, respectively. The magnetocaloric performances are checked by the maximum magnetic entropy change, relative cooling power, and temperature-averaged entropy change with 5 K lift, which are found to be 14.16 J/kgK, 375.55 J/kg and 13.89 J/kgK for HoOCl, to be 14.88 J/kgK, 488.14 J/kg, and 14.60 J/kgK for DyOCl, to be 14.59 J/kgK, 419.67 J/kg, and 14.42 J/kgK for TbOCl, and to be 16.16 J/kgK, 213.68 J/kg, and 14.39 J/kgK for GdOCl, with the magnetic field change of 0–7 T, respectively. [ABSTRACT FROM AUTHOR]

We herein investigated four rare earth (RE)-based oxides, the RE 2 SiO 5 (RE = Gd, Dy, Ho, and Er) silicates, regarding their structural and cryogenic magnetic properties. All the RE 2 SiO 5 silicates are found to crystallized in a monoclinic structure. X-ray photoemission spectroscopy spectra illustrate that RE , Si and O elements in RE 2 SiO 5 silicates are present as RE 3+, Si4+, and O2−, respectively. The Dy 2 SiO 5 reveals a first-order magnetic transition around 4.5 K. The magnetic phase transition temperatures are probably below 2 K for the RE 2 SiO 5 (RE = Gd, Ho, and Er) silicates. Large cryogenic magnetocaloric effects (MCE) and good magnetocaloric performances were observed in the RE 2 SiO 5 silicates. The MCE parameters in terms of the maximum magnetic entropy changes, the temperature-averaged entropy change (5 K-lift) and refrigerant capacity under a magnetic field change of 0–5 T are determined to be 35.5, 30.4 J/kgK, and 215.7 J/kg for Gd 2 SiO 5 , to be 13.3, 12.9 J/kgK, and 190.5 J/kg for Dy 2 SiO 5 , to be 15.3, 15.1 J/kgK, and 274.1 J/kg for Ho 2 SiO 5 and to be 17.9, 16.5 J/kgK, and 181.14 J/kg for Er 2 SiO 5 , respectively. These derived values of MCE parameters of the RE 2 SiO 5 silicates, especially for Gd 2 SiO 5 , are at similarly high level with or better than those of the updated candidate materials, making them also of potential for practical magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

The crystal structure, microstructure, magnetic phase transitions and magnetocaloric effect (MCE) in KNaSnF6-type GdCrWO 6 and ErCrWO 6 oxides have been investigated. Both GdCrWO 6 and ErCrWO 6 oxides are confirmed to crystalize in a polar aeschynite type structure with the space group of Pna 2 1 (No.33, oP36). The grain size remains relatively average according to the SEM graph. Under low magnetic field of 0.1 T, the ErCrWO 6 oxide undergoes two successive magnetic transitions around 22 and 7 K, whereas only a weak magnetic transition around 6 K can be noticed. The paramagnetic Curie temperatures θ p are fitted to be −17.0 and −16.6 K for GdCrWO 6 and ErCrWO 6 oxides, respectively, suggesting that the antiferromagnetic (AFM) interaction is dominant at ground state. With the magnetic field change (ΔH) of 0–7 T, the peak value of magnetic entropy change (-ΔS M), refrigeration capacity (RC), relative cooling power (RCP) and 5 K lift temperature-averaged ΔS M (TEC) are figured to be 9.13 J/kg-K, 152 J/kg, 190 J/kg and 9.07 J/kg-K for GdCrWO 6 as well as to be 5.3 J/kg-K, 128 J/kg, 161 J/kg and 5.09 J/kg-K for ErCrWO 6 , respectively. The MCE parameters for GdCrWO 6 and ErCrWO 6 oxides are comparable with recently reported RE -based MCE oxides, indicating present GdCrWO 6 and ErCrWO 6 oxides also considerable for cryogenic magnetic refrigeration (MR). [ABSTRACT FROM AUTHOR]

• The RE 2 Ga 2 Mg (RE = Tm, Er, Ho) compounds were fabricated. • The magnetic and magnetocaloric properties were investigated. • Large conventional and inverse magnetocaloric effects were observed. • The Tm 2 Ga 2 Mg is considerable for cryogenic magnetic cooling. The Mo 2 FeB 2 -type compounds RE 2 Ga 2 Mg (RE = Tm, Er, Ho) (space group P 4/ mbm) exhibit a large magnetocaloric (MC) effect which makes them promising for use in cryogenic magnetic cooling applications. They exhibit low temperature metamagnetic nature below their Néel temperatures of 6.8, 11.7 and 18.4 K for Tm 2 Ga 2 Mg, Er 2 Ga 2 Mg and Ho 2 Ga 2 Mg, respectively. The magnetic entropy change, the temperature-averaged entropy change (3 K-lift), and the relative cooling power under a magnetic field change of 0–7 T are 15.6, 15.4 J/kgK and 275.8 J/kg for Tm 2 Ga 2 Mg; 13.2, 13.0 J/kgK and 268.0 J/kg for Er 2 Ga 2 Mg; as well as 9.1, 9.0 J/kgK and 223.0 J/kg for Ho 2 Ga 2 Mg, respectively. [ABSTRACT FROM AUTHOR]

The magnetic refrigeration (MR) by utilizing the magnetocaloric effect (MCE) of magnetic solids has been considered a promising, environmentally benign, energy-efficient cooling technology. However, the lack of promising magnetic substances has slowed the development of its active application. To identify suitable candidate materials, we herein identified the structural and magnetic properties together with the MCE and magnetocaloric performances of rare earth (RE) rich RE 6 Ni 2.25 Al 0.75 (RE = Dy, Ho and Er) compounds. All the RE 6 Ni 2.25 Al 0.75 compounds are confirmed to crystallized in orthogonal Ho 6 Co 2 Ga-type structure and underwent paramagnetic to antiferromagnetic magnetic transitions. Moreover, large direct (conventional) and inverse MCEs have been observed in all the RE 6 Ni 2.25 Al 0.75 compounds. The values of peak magnetic entropy changes, temperature-averaged magnetic entropy changes with 5 K-lift and relative cooling powers under magnetic field change of 0–7 T are evaluated to be − 4.44 J/kg-K, − 4.38 J/kg-K and 230.6 J/kg for Dy 6 Ni 2.25 Al 0.75 , to be − 12.68 J/kg-K, − 12.26 J/kg-K and 378.2 J/kg for Ho 6 Ni 2.25 Al 0.75 , and to be − 17.52 J/kg-K, − 17.33 J/kg-K and 465.7 J/kg for Er 6 Ni 2.25 Al 0.75 , respectively. • The RE6Ni2.25Al0.75 (RE = Dy, Ho and Er) compounds are fabricated. • The structural and magnetic properties were investigated. • Large direct and inverse magnetocaloric effects were observed. • The Er6Ni2.25Al0.75 is considerable for cryogenic magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Rare earth (RE) based RE - TM - X (TM = transition metal elements; X = P - block elements) materials have received continuous attention due to the exhibition of various intriguing magnetic functional characteristics. In this work, a combined experimental and theoretical investigation has been conducted in detail for RE Co 12 B 6 (RE = Ce, Pr, Nd) compounds with regard to their structural and magnetic properties, particularly the magnetocaloric effect and magnetic phase transition (MPT). All of the present RE Co 12 B 6 compounds are found to crystalize in the SrNi 12 B 6 -type structure and with a ferrimagnetic ground state, which is confirmed by density functional theory calculations and magnetization measurements. The magnetic moments of RE atoms and Co atoms tend to be in antiparallel alignment, and the MPT of these materials originates primarily from the spin-polarized 3 d electrons of the Co atoms, which can be greatly affected by the 4 f electrons of RE atoms. Considerable magnetocaloric effects have been observed around its own T C of 130, 157, and 160 K, for CeCo 12 B 6 , PrCo 12 B 6 , and NdCo 12 B 6 , respectively, which is related to a typical second-order MPT. The corresponding maximum magnetic entropy change and relative cooling power values,with field changes of 0–70 kOe, are determined to be 2.54, 2.84, and 2.77 J/kg K and 116.8, 156.2, and 155.1 J/kg, respectively. The MPT properties of present RE Co 12 B 6 compounds were studied in further detail by critical analysis using the modified Arrott Plot and Kouvel-Fisher methods, which can be explained within the frame of the 3D Heisenberg model with short-range magnetic interaction. [Display omitted] [ABSTRACT FROM AUTHOR]

The structural, magnetic, and magnetocaloric properties of Ni 44 Mn 45-x Sn 11 Fe x (x = 0, 1, 2 and 3) Heusler alloys have been studied detailly by means of X-ray diffraction, differential scanning calorimetry, and magnetization measurements. The martensitic transition temperature (T M) and austenite Curie temperature (T A C) increase gradually with increasing Fe content. Large differences in magnetization between the ferromagnetic austenite and weakly magnetic martensite phases and obvious thermal hysteresis have also been observed during the martensite transformation. With the magnetic field change up to 0–7 T, the maximum value of magnetic entropy changes reaches 26.7 and 23 J kg−1K−1 for x = 1 and 2, respectively, which are much larger than the undoped sample (9.8 J kg−1K−1). Whereas, the effective refrigerant capacity RC eff reduced due to Fe doping increased the hysteresis loss. The alloy for x = 1 has highest RC value of 172 (255) J kg−1 for a magnetic field change of 0–5 T (0–7 T), furthermore, a large magnetic entropy change and moderate RC eff has been obtained around room temperature. • Fe-doped Ni44Mn45-xSn11Fex (x = 0, 1, 2 and 3) Heusler alloys were fabricated. • Structural and magnetic properties of Ni44Mn45-xSn11Fex were investigated. • Considerable magnetocaloric performances in Ni44Mn44Sn11Fe were realized. [ABSTRACT FROM AUTHOR]