EPR Study of the Two-Dimensional Quantum System $Cu(en)(H_2O)_2SO_4$

The angular dependence of electron paramagnetic resonance spectra of $Cu(en)(H_2O)_2SO_4$ single crystals was studied in the X-band frequency range at temperatures 4 and 300 K. Analysis of the linewidth at 300 K revealed nice agreement with the angular variation of the g-factor. This coincidence is the manifestation of the symmetric and antisymmetric exchange coupling, as main broadening mechanisms in $Cu(en)(H_2O)_2SO_4$ at high temperatures. The radical change of the angular dependence of the linewidth observed at 4 K can be ascribed to dipolar coupling.