Electron spin resonance experiments on an S = 52 linear chain antiferromagnet in high frequencies and fields

We report the results of electron spin resonance (ESR) measurements on a typical S = 5/2 linear-chain Heisenberg antiferromagnet, (CH 3 ) 4 NMnCl 3 (TMMC) at high frequencies and fields applied along the chain axis. We have observed an ESR signal whose frequency (v) versus field (H) relation is expressed by hv = √g 2 μ B 2 H 2 + C with g = 2.17. This large shift of g value from 2.00 is discussed on the basis of spin wave theory