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Reported here is a systematical investigation on the crystal structure, magnetic properties and magnetocaloric (MC) effect of three rare earth (RE) molybdate RE 2 MoO 6 (RE = Dy, Tb and Gd) oxides. The X-ray powder diffraction and the morphology as examined using the scanning electron microscope indicate phase-pure and polycrystalline nature of these oxides. The temperature (2–100 K) and magnetic field (up to 5 T) dependence of the magnetic measurements determine the magnetic phase transition (MPT) and MC properties. All the present RE 2 MoO 6 oxides crystallize in a monoclinic structure belonging to C 2/ c space group with the antiferromagnetic ordering at low temperature. Moreover, the RE 2 MoO 6 oxides hold reasonable values of MC parameters including the maximum isothermal magnetic entropy change/temperature-averaged entropy change (2 K lift) and relative cooling power values have been evaluated with the magnetic change of 0–5 T, yielding 17.22 (17.08) J/kgK and 277.67 J/kg for Dy 2 MoO 6 , 17.03 (16.83) J/kgK and 261.12 J/kg for Tb 2 MoO 6 , as well as 27.68 (26.69) J/kgK and 228.14 J/kg for Gd 2 MoO 6 , respectively. These acceptable MC parameters make the present RE 2 MoO 6 oxides potential candidates for cryogenic magnetic refrigeration (MR). [ABSTRACT FROM AUTHOR]

The magnetocaloric effect (MCE) has been extensively studied in various magnetic solids, aiming to both facilitate practical applications in magnetic cooling and deepen our understanding these materials' intrinsic properties. This study presents a systematic investigation of Gd 2 Ti 2 O 7 oxide, characterized by a geometrically frustrated magnetic structure, focusing on its structural and magnetic characteristics through experimental analysis and theoretical calculations. Emphasis is placed on its magnetic phase transition (MPT) and magnetocaloric properties, scrutinizing temperatures as low as 0.4 K and magnetic fields up to 16 T. The results reveal that Gd 2 Ti 2 O 7 oxide possesses a crystalline cubic pyrochlore-type structure with an antiferromagnetic (AFM) semiconductor ground state. The material undergoes a first-order MPT in low field and low-temperature regimes, transitioning to a second-order MPT above 2 K up to 16 T. Evaluation of magnetocaloric parameters, including maximum magnetic entropy change, temperature-averaged entropy change, relative cooling power, and refrigerant capacity, indicates moderate values under low magnetic field changes, while significantly large values are achievable under high magnetic field changes. This finding suggests that potential cryogenic magnetocaloric materials (MCMs) with optimal performance should exhibit low MPT temperatures induced by magnetic frustration and possess a ground state with a sufficiently large magnetic moment induced by low magnetic fields, thus avoiding excessively strong AFM coupling. This study lays the groundwork for future cryogenic MCM design and provides valuable insights into the intrinsic properties of geometrically frustrated magnetic materials. [Display omitted] [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 magnetic properties and magnetic entropy change of amorphousized Tm 60 Co 20 Ni 20 ribbon were systematically studied. The results indicate that the Tm 60 Co 20 Ni 20 amorphous ribbon reveals a second order magnetic transition (paramagnetic to ferromagnetic state) based on the Arrott plots and rescaled magnetic entropy change curves. A large magnetic entropy change is achieved around its Curie temperature of T C ∼6.7 K. Under the magnetic field change (Δ Η ) of 0–5 T, the maximum values of magnetic entropy change (−Δ S M max ) and relative cooling power ( RCP ) are 17.1 J/kg K and 273 J/kg, respectively. In particular, under a relative low Δ Η of 0–2 T, a large magnetic entropy change of 11.8 J/kg K reaches, making it attractive in the field of low-temperature magnetic refrigeration. [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]

The crystal structure together with the magnetic and magnetocaloric properties in RE 2 Ni 1.5 Ga 2.5 (RE = Dy, Ho, Er and Tm) have been investigated systematically. All the RE 2 Ni 1.5 Ga 2.5 compounds crystallize in a CaIn 2 -type structure of (P63/mmc space group). A second-ordered magnetic phase transition (SOPT) from ferromagnetic to paramagnetic (FM to PM) is occurred in RE 2 Ni 1.5 Ga 2.5 compounds with the Curie temperatures (T C) of approximately 16.1, 10.6, 4.1 and below 2 K for RE of Dy, Ho, Er and Tm, respectively. The magnetocaloric parameters including magnetic isothermal entropy change/temperature-averaged magnetic entropy change -Δ S M max/ TEC (5) and relative cooling power RCP are calculated with the values of 10.01/9.92 J/kg K and 418.6 J/kg for Dy 2 Ni 1.5 Ga 2.5 , 20.12/19.65 J/kg K and 644.1 J/kg for Ho 2 Ni 1.5 Ga 2.5 , 18.07/17.69 J/kg K and 447.1 J/kg for Er 2 Ni 1.5 Ga 2.5 , as well as 18.22/16.75 J/kg K and 330.7 J/kg for Tm 2 Ni 1.5 Ga 2.5 with magnetic field change (Δ H) of 0–7 T, respectively. Notably, Ho 2 Ni 1.5 Ga 2.5 exhibits ralatively high magnetocaloric parameters, which suggests that Ho 2 Ni 1.5 Ga 2.5 is a competitive candidate among the MCE materials in the field of cryogenic magnetic refrigeration (MR). • Magnetic properties and MCE in RE 2 Ni 1.5 Ga 2.5 compounds were studied. • Large values of -ΔS M max, TEC and RCP were observed at low temperature. • Ho 2 Ni 1.5 Ga 2.5 compound is competitive for cryogenic magnetic cooling. [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]

CsCl-type HoZn undergoes two successive magnetic phase transitions: (i) paramagnetic to ferromagnetic (FM) at T C ∼ 72 K and (ii) a spin reorientation (SR) at T SR ∼ 26 K. Magnetization and modified Arrott plots indicate that HoZn undergoes a second-order magnetic phase transition around T C . The obtained critical exponents have some small deviations from the mean-field theory, indicating a short range or a local magnetic interaction which is properly related to the coexistence of FM and SR transitions at low temperature. Two successive magnetic transitions in HoZn induce one broad pronounced peak together with a shoulder in the temperature dependence of the magnetic entropy change −Δ S M ( T ) curves, resulting in a wide temperature range with a large relative cooling power ( RCP ). For a field change of 0–7 T, the maximum value of −Δ S M is 15.2 J/kg K around T C with a large RCP value of 1124 J/kg. The large reversible magnetocaloric effect (MCE) and RC indicate that HoZn is a good candidate for active magnetic refrigeration. [ABSTRACT FROM AUTHOR]

We herein fabricated the (Dy 0.25 Ho 0.25 Er 0.25 Tm 0.25) 2 Cu 2 In high-entropy (HE) compounds and systematically determined its structural, magnetic, and magnetocaloric properties. The (Dy 0.25 Ho 0.25 Er 0.25 Tm 0.25) 2 Cu 2 In HE compound was found to crystalize in a tetragonal Mo 2 B 2 Fe type structure (P4/ mbm space group) and undergoes typical second order type magnetic transition. Large MCE and prominent cryogenic magnetocaloric performances were observed in (Dy 0.25 Ho 0.25 Er 0.25 Tm 0.25) 2 Cu 2 In HE compound. The evaluated values of magnetic entropy change and refrigerant capacity of (Dy 0.25 Ho 0.25 Er 0.25 Tm 0.25) 2 Cu 2 In HE compound under magnetic field change of 0–7 T are 17.1 J/kgK and 398.0 J/kg which are comparable with the reported candidate materials for cryogenic magnetic cooling, making the present (Dy 0.25 Ho 0.25 Er 0.25 Tm 0.25) 2 Cu 2 In HE compound also considerable for practical applications. • The (Dy 0.25 Ho 0.25 Er 0.25 Tm 0.25) 2 Cu 2 In HE compound was fabricated. • The structural, magnetic, MPT and MC properties were investigated. • The present HE compound is considerable for cryogenic magnetic cooling. [ABSTRACT FROM AUTHOR]

In this study, two Mo 2 FeB 2 -type multiple rare-earth-containing MRE 2 Cu 2 In (MRE = Dy 1/3 Ho 1/3 Er 1/3 and Ho 1/3 Er 1/3 Tm 1/3 ; space group P 4/ mbm , No. 127) compounds are prepared via arc-melting method and systematically determined regarding their structural and magnetic properties, magnetic phase transition (MPT), and magnetocaloric (MC) performances. They undergo typical second-order MPT at low temperatures. The MC effect and MC performances of the present MRE 2 Cu 2 In compounds at low temperatures are assessed using magnetic entropy changes, refrigerant capacity, and temperature-averaged entropy changes. The values of these parameters are comparable to most updated candidate materials for low-temperature magnetic cooling, making the present MRE 2 Cu 2 In compounds considerable for practical applications. • The MRE 2 Cu 2 In (MRE = Dy 1/3 Ho 1/3 Er 1/3 and Ho 1/3 Er 1/3 Tm 1/3) compounds are fabricated. • The structural, magnetic, MPT and MC properties in MRE 2 Cu 2 In were studied. • These MRE 2 Cu 2 In compounds are considerable for cryogenic magnetic refrigeration. [ABSTRACT FROM AUTHOR]

• The gallides RE 2 Rh 3 Ga (RE = Gd, Dy, Ho, Er) compounds are fabricated. • The structural, MPT and magnetocaloric properties in RE 2 Rh 3 Ga were studied. • The present RE 2 Rh 3 Ga compound are considerable for cryogenic MR. We herein provide an experimental investigation of the gallides RE 2 Rh 3 Ga (RE = Gd, Dy, Ho, Er) regarding their magnetic properties and magnetocaloric effect (MCE). All of these RE 2 Rh 3 Ga intermetallic compounds crystallized with the Mg 2 Ni 3 Si type structure, space group R– 3 m and are ordered magnetically at low temperatures. Large reversible MCEs around their own ordering temperature were observed in all RE 2 Rh 3 Ga compounds and their magnetocaloric parameters including the maximum magnetic entropy change, refrigerant capacity, and temperature-averaged entropy change are comparable to those of some recently reported candidate materials with prominent performances, making them considerable for cryogenic MR applications. [ABSTRACT FROM AUTHOR]

We fabricated the amorphous Ho 0.2 Tm 0.2 Gd 0.2 Co 0.2 Al 0.2 ribbon by melt-spun method and systematically investigated its glass forming ability (GFA) and magnetic properties, especially of the magnetic phase transition (MPT) and magneto-caloric (MC) effect. The melt-spun Ho 0.2 Tm 0.2 Gd 0.2 Co 0.2 Al 0.2 ribbon is found to exhibit a fully amorphous structure and good GFA. The amorphous Ho 0.2 Tm 0.2 Gd 0.2 Co 0.2 Al 0.2 ribbon undergoes a second order type MPT around 32.6 K from ferromagnetic to paramagnetic state. Large reversible low temperature MC effect and good MC performances in the amorphous Ho 0.2 Tm 0.2 Gd 0.2 Co 0.2 Al 0.2 ribbon were realized which was identified by the parameters of magnetic entropy change, temperature-averaged entropy change, and refrigerant capacity. These parameters are are at similarly high level with recently reported low temperature MC materials, making the amorphous Ho 0.2 Tm 0.2 Gd 0.2 Co 0.2 Al 0.2 ribbon also attractive for magnetic cooling. [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 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]