Susceptibility and high-field magnetization of one-dimensional S = 1/2 Heisenberg antiferromagnet with next-nearest exchange interaction

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-chai n exchange parameters which characterize the frustrated zigzag chain were e valuated. The coupling ratio j = \J'/J\ = 0.2 is found to be subcritical, a nd to be very near the critical ratio j(c) = 0.241 above which the spin-gap ped phase is predicted. In fact, no spin gay was found, consistent with the prediction. (C) 2000 Elsevier Science B.V. All rights reserved.