Search

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]

In this study, we present the crystal structure, magnetic properties, and cryogenic magneto-caloric effect (MCE) of RE 2 FeAlO 6 (RE = Gd, Dy, Ho) oxides. The XRD refinement analysis suggests that all the RE 2 FeAlO 6 oxides are crystallized in B-site disordered orthorhombic structure. The RE 2 FeAlO 6 oxides exhibit large MCEs around T C. The peak magnetic entropy change (-Δ S M) and refrigeration capacity (RC) are 25.9 J/(kgK) and 240.1 J/kg for Gd 2 FeAlO 6 , 10.7 J/(kgK) and 274.9 J/kg for Dy 2 FeAlO 6 , 9.6 J/(kgK) and 249.6 J/kg for Ho 2 FeAlO 6 under Δ H of 0–70 kOe, respectively. Notably, Gd 2 FeAlO 6 exhibits promising magneto-caloric performance and therefore is a favorable candidate for cryogenic magnetic refrigeration. [ABSTRACT FROM AUTHOR]

In this work, we fabricated the RE 2 O 2 SO 4 (RE = Gd, Tb, Dy and Ho) oxides by thermal decomposition and systematically determined regarding their structural and magnetic properties, especially of the magnetic phase transition (MPT) and magnetocaloric effect (MCE). All of these RE 2 O 2 SO 4 oxides are confirmed to crystallize in an orthogonal structure (space group: pmnb); the constituting elements are all distributed uniformly and presented as the RE 3+, S6+, and O2− valence states, respectively. They all exhibit a typical cryogenic MPT from paramagnetic to antiferromagnetic (AFM) state together with a field-induced metamagnetic transition (first-order type MPT) from AFM to ferromagnetic state below their MPT temperatures. All of these RE 2 O 2 SO 4 oxides exhibit considerable direct and inverse cryogenic MCE. The determined direct magnetocaloric parameters of present RE 2 O 2 SO 4 oxides, especially of Gd 2 O 2 SO 4 and Ho 2 O 2 SO 4 oxides, are comparable with most of recently reported RE -based magnetic solids, making them also considerable for practical cryogenic MR applications. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect has been extensively investigated in various types of magnetic solids to not only develop practical magnetic cooling applications but also deepen the understanding of these materials' underlying inherent properties. Through experimental determination and theoretical calculation, we conducted a systematic investigation of Gd 4 Ga 2 O 9 oxide in terms of its structural, magnetic, and magnetocaloric properties and found it to crystallize in a monoclinic structure belonging to the space group P 2 1 / c and to possess an antiferromagnetic semiconducting ground state. The consistent elements were uniformly distributed up to the nanoscale and presented as Gd3+, Ga3+, and O 2 states, respectively. The magnetocaloric performances of Gd 4 Ga 2 O 9 oxide were checked according to the parameters of maximum magnetic entropy change, refrigerant capacity, and temperature-averaged entropy changes (lift of 5 K), which were determined to be 25.77 J/kgK, 218.27 J/kg, and 23.43 J/kgK under 0–7 T magnetic field change. These parameters of Gd 4 Ga 2 O 9 oxide are comparable to those of some recently reported materials with prominent performances, which means that it can be considered for cryogenic magnetic cooling applications. [ABSTRACT FROM AUTHOR]

We herein fabricated two gadolinium-transition metal-based high entropy (HE) oxides of Gd(Mn 0.25 Fe 0.25 Al 0.25 Cr 0.25)O 3 [denoted as Gd(4 TM 0.25)O 3 ] and Gd(Mn 0.2 Fe 0.2 Al 0.2 Co 0.2 Ni 0.2)O 3 [denoted as Gd(5 TM 0.2)O 3 ] and determined their structural, magnetic, and magnetocaloric properties. Both of present HE oxides are found to crystallize in the single-phase perovskite-type orthorhombic structure with a homogeneous microstructure and exhibit prominent cryogenic magnetocaloric performances. The values of magnetic entropy change, refrigerant capacity, and temperature-averaged entropy change (6K-lift) under the magnetic field change of 0–7 T are estimated to be 20.34 J/kgK, 295.4 J/kg, and 19.56 J/kgK for Gd(4 TM 0.25)O 3 , and to be 22.45 J/kgK, 258.2 J/kg, and 20.79 J/kgK for Gd(5 TM 0.2)O 3 , respectively, which are comparable with recently reported candidate materials for practical magnetic cooling. These findings not only indicate potential applications of present perovskite-type Gd(4 TM 0.25)O 3 and Gd(5 TM 0.2)O 3 HE oxides, but also provide meaningful clues for exploring HE oxides with prominent cryogenic magnetocaloric performances. [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 magnetic refrigeration (MR) based on magnetocaloric effect (MCE) is a key technique, since it possesses ideally higher performance than the traditional gas compression technology. However, the lack of MR materials with excellent MCE performance is a bottle-neck for practical MR applications. Herein, we systematically report the structural properties using powder X-ray diffraction and scanning electron microscope as well as the magnetic and magnetocaloric properties through the magnetization measurements of four rare-earth (RE) ruthenate RE 3 RuO 7 (RE = Pr, Nd, Gd and Tb) compounds. Light RE -based Pr 3 RuO 7 and Nd 3 RuO 7 compounds form an orthorhombic Cmcm structure, while heavy RE based Gd 3 RuO 7 and Tb 3 RuO 7 compounds crystallize in an orthorhombic P 2 1 nb structure. The magnetic phase transition of all the present compounds are confirmed to be of the first-order type with T N of 52, 15, 11 and 12 K for Pr 3 RuO 7 , Nd 3 RuO 7 , Gd 3 RuO 7 and Tb 3 RuO 7 compounds, respectively. The related MCE parameters including the maximum isothermal magnetic entropy change, temperature-averaged entropy change (5 K lift), and refrigerant capacity with the magnetic field change of 0–5 T were computed to be 1.35 J/kgK, 1.31 J/kgK, and 27.4 J/kg for Pr 3 RuO 7 , to be 2.18 J/kgK, 2.04 J/kgK, and 25.6 J/kg for Nd 3 RuO 7 , to be 8.12 J/kgK, 7.90 J/kgK, and 124.6 J/kg for Gd 3 RuO 7 , and to be 7.78 J/kgK, 7.49 J/kgK, and 128.8 J/kg for Tb 3 RuO 7 , respectively. [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]