Spin dynamics in S frac1 2 chains with next nearest neighbor exchange interactions

摘要

Low energy magnetic excitations in the S 1 2 chain compound [ C6H9N2 CuCl3]CuCl3 [known as 6MAP CuCl3] are probed by means of tunable frequency electron spin resonance. Two modes with asymmetric with respect to the h g B B line frequency field dependences are resolved, illuminating the striking incompatibility with a simple uniform S 1 2 Heisenberg chain model. The unusual ESR spectrum is explained in terms of the recently developed theory for S 1 2 chains, suggesting the important role of next nearest neighbor interactions in this compound. Our conclusion is supported by model calculations for the magnetic susceptibility of 6MAP CuCl3, revealing a good qualitative agreement with experiment