“…Bhatti et al found reported similar Griffith phase behavior in nanocrystalline Gd 2 CoMnO 6 . The deviation from the Curie–Weiss law fitting of χ −1 increases with magnetic disorder, which is caused by the various ionic sizes of rare earth elements in current double perovskites 32 . Figure 3 ( a ) The temperature dependent magnetization under the magnetic field of 100 Oe.…”
The crystal structure, cryogenic magnetic properties, and magnetocaloric performance of double perovskite Eu2NiMnO6 (ENMO), Gd2NiMnO6 (GNMO), and Tb2NiMnO6 (TNMO) ceramic powder samples synthesized by solid-state method have been investigated. X-ray diffraction structural investigation reveal that all compounds crystallize in the monoclinic structure with a P21/n space group. A ferromagnetic to paramagnetic (FM-PM) second-order phase transition occurred in ENMO, GNMO, and TNMO at 143, 130, and 112 K, respectively. Maximum magnetic entropy changes and relative cooling power with a 5 T applied magnetic field are determined to be 3.2, 3.8, 3.5 J/kgK and 150, 182, 176 J/kg for the investigated samples, respectively. The change in structural, magnetic, and magnetocaloric effect attributed to the superexchange mechanism of Ni2+–O–Mn3+ and Ni2+–O–Mn4+. The various atomic sizes of Eu, Gd, and Tb affect the ratio of Mn4+/Mn3+, which is responsible for the considerable change in properties of double perovskite.
“…Bhatti et al found reported similar Griffith phase behavior in nanocrystalline Gd 2 CoMnO 6 . The deviation from the Curie–Weiss law fitting of χ −1 increases with magnetic disorder, which is caused by the various ionic sizes of rare earth elements in current double perovskites 32 . Figure 3 ( a ) The temperature dependent magnetization under the magnetic field of 100 Oe.…”
The crystal structure, cryogenic magnetic properties, and magnetocaloric performance of double perovskite Eu2NiMnO6 (ENMO), Gd2NiMnO6 (GNMO), and Tb2NiMnO6 (TNMO) ceramic powder samples synthesized by solid-state method have been investigated. X-ray diffraction structural investigation reveal that all compounds crystallize in the monoclinic structure with a P21/n space group. A ferromagnetic to paramagnetic (FM-PM) second-order phase transition occurred in ENMO, GNMO, and TNMO at 143, 130, and 112 K, respectively. Maximum magnetic entropy changes and relative cooling power with a 5 T applied magnetic field are determined to be 3.2, 3.8, 3.5 J/kgK and 150, 182, 176 J/kg for the investigated samples, respectively. The change in structural, magnetic, and magnetocaloric effect attributed to the superexchange mechanism of Ni2+–O–Mn3+ and Ni2+–O–Mn4+. The various atomic sizes of Eu, Gd, and Tb affect the ratio of Mn4+/Mn3+, which is responsible for the considerable change in properties of double perovskite.
Structural, magnetic and dielectric properties have been studied for Yb 2 CoMnO 6 . Nano-crystalline sample of Yb 2 CoMnO 6 synthesized by sol-gel method and structural analysis shows that the sample crystallizes in monoclinic crystal structure with P2 1 /n phase group. To understand the charge state of Co, Mn and Yb we have performed the XPS study. Magnetic study shows that the sample undergoes a paramagnetic to ferromagnetic phase transition around T c ∼56 K and an additional magnetic ordering at a lower temperature around 14 K due to ordering of Yb 3+ magnetic ions. Temperature dependent Raman study reveals that spin-phonon interaction is present in this material. Further, we have studied the dielectric properties of this material. We observed that the material shows a relaxation behavior that obeys the thermally activated relaxation mechanism. Impedance spectroscopy reveals that the material shows non-Debye's behavior. AC conductivity study is performed to understand the conduction mechanics which involve the quantum mechanical tunneling phenomenon.
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