Susceptibility and high-field magnetization of one-dimensional [formula omitted] Heisenberg antiferromagnet with next-nearest exchange interaction

Abstract

The magnetic susceptibility and high-field magnetization of S= 1 2 zigzag antiferromagnetic chain compound Cu[2-(2-aminomethyl)pyridine]Br 2 (Cu(ampy)Br 2) were measured. The nearest J and next-nearest neighbor J′ intra-chain exchange parameters which characterize the frustrated zigzag chain were evaluated. The coupling ratio j=| J′/ J|=0.2 is found to be subcritical, and to be very near the critical ratio j c=0.241 above which the spin-gapped phase is predicted. In fact, no spin gap was found, consistent with the prediction.