High field ESR measurements on the low dimensional S = 1/2 Heisenberg antiferromagnet (CPA)2CuBr4

Abstract

ESR measurements have been performed on poly crystalline sample of an S = 1/2 Heisenberg antiferromagnetic ladder-like system (C5H9NH3)2CuBr4. We estimated the g-value as g = 2.20 from analysis of a broad absorption line at high temperatures. Multiple ESR absorption lines were observed below 10 K. The ESR modes show non-linear frequency dependence of the resonance field at 4 K, and the temperature dependence of the line width with a thermal activation type formula. The ESR modes observed are well explained by the theoretical model of the breather excitation.