Exact Dimer Ground State and Quantized Magnetization Plateaus in the Two-Dimensional Spin System SrCu2\(BO3\) 2

Magnetic susceptibility, Cu NQR, and high-filed magnetization have been measured in polycrystalline SrCu ₂\(BO ₃\)₂ having a two-dimensional (2D) orthogonal network of Cu dimers. This cuprate provides a new class of 2D spin-gap system \(Δ = 30 K\) in which the ground state can be solved ``exactly.'' Furthermore, in the magnetization, two plateaus corresponding to 14 and 18 of the full Cu moment were first observed for 2D quantum spin systems.