An X-band and Q-band single crystal electron paramagnetic resonance study of CuCl 2·2H 2O

Abstract

Room temperature electron paramagnetic resonance (EPR) measurements were carried out on single crystals of CuCl 2·2H 2O around their three crystallographic axes at X-band (9.5 GHz) and Q-band (35 GHz). Owing to the interchain exchange interaction which is stronger than the difference in Zeeman energies of the dissimilar ions, the EPR spectrum is always reduced to a Lorentzian singlet, not only at X-band, but even at Q-band. There is no frequency dependence of the g factors from X-band to Q-band. The sinusoidal angular dependence of g 2 in any plane is related to the fact that the relative anisotropy Δ g/ g is moderate in the a, c plane. The angular dependence of the linewidth is analyzed, namely in the a, c plane, where the interchain contribution Δ H 12 is extracted from the total linewidth Δ H. This permits us to determine the following value of the interchain exchange interaction: J′/ k = (0.40 ± 0.04)K, from which we conclude that the single crystal EPR study at Q-band provides a direct and precise method to determine the exchange interaction J′ between inequivalent copper ions.