High-field Magnetism of the Honeycomb-lattice Antiferromagnet Cu${}_2$(pymca)${}_3$(ClO${}_4$)

Abstract

We report on the experimental results of magnetic susceptibility, specific heat, electron spin resonance (ESR), and high-field magnetization measurements on a polycrystalline sample of the spin-$1/2$ distorted honeycomb-lattice antiferromagnet Cu${}_2$(pymca)${}_3$(ClO${}_4$). Magnetic susceptibility shows a broad peak at about 25~K, which is typical of a low dimensional antiferromagnet, and no long range magnetic order is observed down to 0.6~K in the specific heat measurements. Magnetization curve up to 70~T at 1.4~K shows triple stepwise jumps. Assuming three different exchange bonds $J_{\mathrm{A}}$, $J_{\mathrm{B}}$ and $J_{\mathrm{C}}$ from the structure, the calculated magnetization curve reproduces the observed one when $J_{\mathrm{A}}/k_{\mathrm{B}}=43.7\mathrm{K}$, $J_{\mathrm{B}}/J_{\mathrm{A}}=1$ and $J_{\mathrm{C}}/J_{\mathrm{A}}=0.2$ except the magnetization near 70~T, where the observed magnetization indicates another step while the calculated magnetization becomes saturated. The relationship between magnetization plateaus and exchange bonds is discussed based on the numerical calculations.

5 pages, 5 figures