Vanadium Octacyanoniobate-Based Magnet with a Curie Temperature of 138 K

In this work, we prepared a three-dimensional vanadium octacyanoniobate-based magnet, K<sub>0.10</sub>V<sup>II</sup><sub>0.54</sub>V<sup>III</sup><sub>1.24</sub>[Nb<sup>IV</sup>(CN)<sub>8</sub>]·(SO<sub>4</sub>)<sub>0.45</sub>·6.8H<sub>2</sub>O. This compound exhibits ferrimagnetism with a Curie temperature of 138 K, in which the sublattice magnetizations of V<sup>II</sup> (<i>S</i> = <sup>3</sup>/<sub>2</sub>) and V<sup>III</sup> (<i>S</i> = 1) are antiparallelly ordered to that of Nb<sup>IV</sup> (<i>S</i> = <sup>1</sup>/<sub>2</sub>). The estimated superexchange interaction constants of V<sup>II</sup>−Nb<sup>IV</sup> and V<sup>III</sup>−Nb<sup>IV</sup> are −51 and −25 cm<sup>−1</sup>, respectively.