Search

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]

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]

In this work, polycrystalline oxides viz., Ho 2 CrMnO 6 (HCMO) and Er 2 CrMnO 6 (ECMO), were prepared using the sol-gel process, and their crystal structure, magnetic properties, and magnetocaloric effects (MCEs) were studied. X-ray refinement results demonstrate that both oxides exhibited the B -site disordered perovskite type structure (Pbnm space group). A ferromagnetic-paramagnetic phase transition as well as large reversible MCEs was also observed at Curie temperatures (T C) of ~6.1 and ~5.2 K for HCMO and ECMO, respectively. For a magnetic field change (ΔH) of 0–7 T, the maximum magnetic entropy change (-Δ S M), temperature-averaged entropy change (TEC 3), and relative cooling power (RCP) were estimated to be 11.03 J/kgK, 11.02 J/kgK, and 322.7 J/kg for HCMO, and 12.94 J/kgK, 12.80 J/kgK and 277.5 J/kg for ECMO. [ABSTRACT FROM AUTHOR]