ESR Studies on CaV₄O₉ and CaV₃O₇

Abstract

ESR measurements have been performed on single crystals of two-dimensional S=1/2 systems of CaV₄O₉ and CaV₃O₇.The linewidths of their ESR spectra can be described by the form of ( A cos ² θ + B ), where θ is the angle between the directions of the c-axis and the external magnetic field and A and B are material dependent positive constants.The results seem to be understood by introducing the broadening due to the Dzyaloshinsky-Moriya interaction with exchange narrowing.The resonance field has been found to depend not only on θ but also on the angle between the directions of the c-axis and the microwave field.This behavior seems to be explained by considering the effect of the non-diagonal dynamical susceptibility expected for systems with low symmetry.