ESR studies of a spin-1/2 ferromagnetic-ferromagnetic-antiferromagnetic-antiferromagnetic tetramer chain

摘要

Electron spin resonance (ESR) measurements have been performed at X-band on a single crystal sample of Cu(3-Clpy){sub}2 (N{sub}3){sub}2 (3-Clpy=3-Chloropyridine) which is regarded as the spin 1/2 ferromagnetic-ferromagnetic- antiferromagnetic- antiferromagnetic tetramer chain. Angular dependence of the line width at half height of the absorption profile at room temperature obeys the diffusive type of angular anisotropy, which means that the minimum of the line width takes place at about 55° between the applied field and the chain direction. The line profile of the signal at 0° or 90° deviates from not only Lorentzian and Gaussian but also the typical one dimensional line profile. The temperature dependence of the resonance field parallel to the chain shows a monotonical shift to low field side upon cooling, while that of the resonance field perpendicular to the chain shows the opposite behavior. Most of these findings indicate that this compound behaves as a typical one-dimensional system like an antiferromagnetic uniform chain irrespective of a peculiar exchange coupling.