Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The magnetic and thermodynamic properties of layered single-crystal K₂Ni(MoO₄)₂ having both structural and magnetic dimers have been investigated. The crystal structure of K₂Ni(MoO₄)₂ is composed of edge-sharing NiO₆-octahedral pairs bridged by the MoO₄ ²⁻ polyatomic ion groups in a plane, and the K⁺ ions sit in the van der Waals gap between the layers. The temperature dependence of magnetic susceptibility shows a spin-singlet ground state with an activation gap of Δ/k_B ≈ 38 K. A high-field magnetization study at T = 1.5 K exhibits a half-magnetization plateau at μ₀H ∼ 25 T, corresponding to a level crossing of the singlet ground state with the lowest triplet state. Further, we have performed density functional theory calculations to determine magnetic exchange interactions. The nearest-neighbor coupling constant J₁ ∼ 10 K between the Ni spins turns out to be an order of magnitude larger than all interdimer couplings. Our experimental and theoretical results suggest that K₂Ni(MoO₄)₂ constitutes a nearly isolated two-dimensional S = 1 dimer model.