High-field Magnetism of the Honeycomb-lattice Antiferromagnet Cu2(pymca)3(ClO4)

We report on the experimental results of magnetic susceptibility, specific heat, electron spin resonance (ESR), and high-field magnetization measurements performed on a polycrystalline sample of the spin-1/2 distorted honeycomb-lattice antiferromagnet Cu-2(pymca)(3)(ClO4). The magnetic susceptibility shows a broad peak near 25 K, typical of a low-dimensional antiferromagnet, and no long-range magnetic order is observed down to 0.6 K in the specific heat measurements. The magnetization curve up to 70T at 1.4 K shows three step-like features. Assuming three different exchange bonds J(A), J(B), and J(C) based on the structure, the calculated magnetization curve reproduces the observed one when J(A)/k(B) = 43.7 K, J(B)/J(A) = 1, and J(C)/J(A) = 0.2, except for the magnetization near 70T, where the observed magnetization indicates another step while the calculated magnetization becomes saturated. The relationship between the magnetization plateaus and exchange bonds is discussed based on the numerical calculations.