Ni12(HPO4)6(PO4)2(OH)6: a compound with coupled frustrated hexagons of alternating ferromagnetic and antiferromagnetic interactions.

Frustrated magnets offer a unique playground for exploring emergent quantum phenomena. We report the synthesis, structural details, and magnetic properties ofS= 1 frustrated system Ni12(HPO4)6(PO4)2(OH)6through magnetization and specific heat measurements along with the density functional theory (DFT) calculations. The titled compound hosts a three-dimensional frustrated spin-lattice wherein Ni2+(S= 1) magnetic moments constitute hexagonal rings. The DFT electronic structure calculation reveals that Ni2+moments in the hexagonal rings have alternate ferromagnetic (FM) and antiferromagnetic (AFM) interactions with considerable inter-hexagonal ring magnetic interactions. The magnetic susceptibilityχ(T) data follow Curie-Weiss (CW) behavior at high temperatures with a large CW temperature of about -250 K, implying the strong AFM interactions between the Ni2+(S= 1) magnetic moments. Theχ(T) and specific heat data show an anomaly at 61 K, indicating the presence of magnetic order. Alternative FM and AFM bonds in the hexagonal ring induce magnetic frustration, and the non-negligible inter-hexagonal ring interactions lead to the long-range magnetic order in the titled compound.