Structural, magnetic, and magnetocaloric properties of R(2)NiMnO(6) (R = Eu, Gd, Tb)

The crystal structure, cryogenic magnetic properties, and magnetocaloric performance of double perovskite Eu(2)NiMnO(6) (ENMO), Gd(2)NiMnO(6) (GNMO), and Tb(2)NiMnO(6) (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 P2(1)/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 Ni(2+)–O–Mn(3+) and Ni(2+)–O–Mn(4+). The various atomic sizes of Eu, Gd, and Tb affect the ratio of Mn(4+)/Mn(3+), which is responsible for the considerable change in properties of double perovskite.