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C2O42--templated [Ln2Ni] heterometallic compounds for enhanced magnetocaloric effects at low fields
Qin Wang1, Lingxi Xu2, Jilei Wang1
1State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211816, P. R. China. yanxu@njtech.edu.cn.
Abstract:
In the history of magnetochemistry development, lanthanide-transition (3d-4f) heterometallic compounds have been considered an attractive candidate for magnetic refrigerants. Herein, a series of heterometallic compounds have been designed and templated by C2O42- anions, that is, {[Ln2Ni(L)(C2O4)2(H2O)2]·H2O} [Ln = GdIII (abbr. Gd2Ni) = SmIII (abbr. Sm2Ni) = TbIII (abbr. Tb2Ni), H2C2O4 = oxalic acid; H4L = ethylene diamine tetraacetic acid]. The structural analysis reveals that Ln2Ni compounds feature a C2O42--templated wavy-shaped two-dimensional layer. Then, adjacent wavy-shaped layers are further aggregated by C2O42- anions, resulting in an innovative three-dimensional metal-organic framework. Magnetization analysis revealed that Gd2Ni exhibits a favorable -ΔSmaxm of 38.0 J kg-1 K-1 at 2.0 K for 7.0 T. In addition, the effect of weak ferromagnetic exchange interactions in Gd2Ni contributes to a decent magnetocaloric effect at low fields (-ΔSm = 25.1 J kg-1 K-1 at 2.0 T for 2.0 K and -ΔSm = 14.5 J kg-1 K-1 at 1.0 T for 2.0 K), outperforming most 3d-4f heterometallic compounds reported previously.
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