Structural, magnetic, and magnetocaloric properties of R2NiMnO6 (R = Eu, Gd, Tb)

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 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 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.

Automated summary

The crystal structure, cryogenic magnetic properties, and magnetocaloric performance of double perovskite materials ENMO, GNMO, and TNMO synthesized by solid-state method were investigated. The different atomic sizes of Eu, Gd, and Tb affect the properties of these perovskites, especially the ratio of Mn4+/Mn3+.