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The multiferroic spinel crystalline ACr2O4(A = Co, Ni) were synthesized via a traditional sol-gel reaction and characterized with respect to the structural, magnetic properties and magnetocaloric performances. The ACr2O4 oxides are confirmed to crystallize in cubic Al2MgO4-type structure with space group Fd 3 ¯ m and tetragonal CdMn2O4-type structure with I41/amdz space group for A = Co, Ni, respectively. Both ACr2O4 compounds reveal a typical second-ordered magnetic transition (SOMT) form paramagnetic to ferromagnetic (PM-FM) around its own Curie temperature TC and followed by a low temperature anomalous which is probably due to the spin glass (SG) transition behavior. The calculated peak values of magnetic entropy change (− ∆SMmax) around its own TC under the external magnetic field changes ΔH = 7 T are 1.54 and 1.19 J·kg−1 K−1 for A = Co, Ni, respectively, and the corresponding relative cooling power (RCP) is 22.2 and 22.33 J·kg−1. [ABSTRACT FROM AUTHOR]

The electromagnetic wave (EMW) absorption properties in Heusler-type ferromagnetic Ni2+xMn1−xGa alloys were systematically investigated. Significant electromagnetic absorption performance at 2.0-18.0 GHz was observed for Ni2+xMn1−xGa alloys. The values of the complex permittivity (εr) and permeability (μr), as well as the reflection loss (RL), peak frequency (fm) and bandwidth (Δf) of Ni2+xMn1−xGa can be effectively tuned by the alloy component (Ni/Mn ratio). The magnetic loss factor (tan δμ) shows pronounced multi-resonance behavior, and dielectric loss factor (tan δε) has dramatic dielectric relaxation. The RL exceeding − 10 dB corresponding to 90% absorption of incident microwave can be achieved for the Ni2MnGa in a broad frequency range of 6.3-18.0 GHz together with the thickness from 1.66 to 4.75 mm. Particularly, the maximum RL reaches − 49.1 dB at 13.3 GHz with the thickness of 2.57 mm for Ni2MnGa. The present results indicated that the ferromagnetic Ni2+xMn1−xGa alloys could be attractive candidates for broadband and high-frequency EMW absorption. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic phase transition and magnetocaloric effect (MCE) of TbCoC and ErCoC were systematically investigated. The compounds are crystallized in tetragonal YCoC-type structure ( P 4/ mmm space group). TbCoC undergoes a second-order paramagnetic to ferromagnetic (PM-FM) magnetic phase transition around its Curie temperature T C  = 22 K, whereas ErCoC has a field-induced first-order antiferromagnetic to ferromagnetic (AFM-FM) magnetic phase transition below Neel temperature T N  = 10 K. Both compounds exhibit large reversible MCE accompanied with the magnetic phase transition. For Δ H  = 0–5 T, the values of − Δ S M m a x (maximum of magnetic entropy change) reach 16.5 and 18.7 J/kg K for TbCoC and ErCoC, respectively, the corresponding values of RCP (relative cooling power) are 470 and 371 J/kg. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic properties and magnetocaloric effect (MCE) in double perovskite R 2 NiMnO 6 ( R = Dy, Ho, and Er) compounds have been investigated. The R 2 NiMnO 6 compounds crystallize in the monoclinic structure belonging to the P2 1 /n space group. Three magnetic phase transitions can be observed for R 2 NiMnO 6 compound. And accordingly, two peaks together with one shoulder are appeared in the temperature dependence of magnetic entropy change Δ S M ( T ) curves. With the magnetic field change of 0–7 T, the maximum values of the magnetic entropy change (−Δ S M max ) for R 2 NiMnO 6 ( R = Dy, Ho, and Er) are 10.9, 11.4, and 12.2 J Kg −1 K −1 at low temperature, and 3.9, 4.2 and 4.8 J Kg −1 K −1 around T C , respectively. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic properties and magnetocaloric effect (MCE) of HoCoC 2 and ErCoC 2 have been investigated. They both crystallize in orthorhombic CeNiC 2 -type structure with Amm 2 space group and a second-order paramagnetic to ferromagnetic phase transition around the Curie temperature T C ∼11 K and ∼14 K occurred in them. Under the magnetic field change (Δ H ) of 0–5 T, the maximal values of magnetic entropy change, refrigerant capacity and relative cooling power are 15.6 J/kg K, 183 J/kg, 242 J/kg for HoCoC 2 and 17.2 J/kg K, 243 J/kg, 375 J/kg for ErCoC 2 , respectively. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic properties and magnetocaloric effect (MCE) in R 2 CoMnO 6 (R = Dy, Ho, and Er) ceramics were investigated. The R 2 CoMnO 6 crystallized in the monoclinic structure belonging to the P 2 1 / n space group. The compounds revealed three magnetic phase transitions, and according three peaks appeared in the temperature dependence of magnetic entropy change curves. A considerable values of maximum magnetic entropy change (-∆ S M max ) and the relative cooling power ( RCP ) for R 2 CoMnO 6 ( R = Dy, Ho, and Er) at low temperature around Curie temperature T C were observed. Moreover, the normalized ∆ S M ( T ) curves around Curie temperature for all the present R 2 CoMnO 6 collapse onto a single universal curve, which confirmed that the observed paramagnetic-ferromagnetic phase transition for all the samples was of a second order. [ABSTRACT FROM AUTHOR]