Magnetic properties of a spin-1/2 mixed coordination lattice

We successfully synthesized (p-Py-V)(2)[Cu(hfac)(N)], a verdazyl-based complex. Molecular orbital calculations revealed that three antiferromagnetic (AF) exchange interactions form a spin-1/2 lattice with coordination numbers 2 and 4. The magnetic susceptibility and specific heat exhibit contributions of AF correlations and a phase transition to an AF ordered state at T-N = 3.6 K. The magnetization curve exhibits an almost linear increase in the low-field region for T > T-N. Furthermore, we observe a nonlinear increase in the high-field region, demonstrating the magnetic moment reduction caused by the strong quantum fluctuations. Through numerical analysis, we reveal a hump structure of magnetic susceptibility and a 1/3 magnetization plateau that emerge owing to the effective spin state. These results provide a model compound forming a spin-1/2 mixed coordination lattice and an understanding of its unique quantum properties attributed to strong quantum fluctuations.