ESR study of frustrated spin chain [Cu(bpy)H2O][Cu(bpy)(mal)H2O](ClO4)2

Abstract

Recently, experimental studies of low dimensional quantum spin systems have attracted much attention due to the discovery of model substances. In this paper, we study new one-dimensional spin system called "delta-chain". The delta-chain is composed of S=l/2 spin trimers and these trimers are stacked like a saw-tooth which is shown in this chapter. The delta chain having antiferromagnetic coupling is considered to be a fully frustrated quantum spin system. Theoretical studies for this spin system have been made to investigate the ground state and the low-lying excitation. The ground state is essentially singlet dimer state and has a high degeneracy due to the full frustration. The low-lying excitation is considered to be a topological excitation, which has a finite energy gap between the ground state, resulting in a Schottkey-type low temperature peak in specific heat and the zero susceptibility at zero temperature. To investigate the magnetic properties and spin dynamics of the delta-chain compound [Cu(bpy)H2O][Cu(bpy)(mal)H2O](ClO4)2, X-band, millimeter and submillimeter ESR measurements were performed at various temperatures.