Spin anisotropy in Cu(en)(H₂O)₂SO₄: A quasi-two-dimensional S = 1/2 spatially anisotropic triangular-lattice antiferromagnet

We have studied in detail the effect of the spin anisotropy on the electron paramagnetic resonance spectra and magnetic properties of Cu(en)(H₂O)₂SO₄, an S = 1/2 spatially anisotropic triangular lattice antiferromagnet. The angular and temperature dependence of the resonance fields as well as the magnetization and magnetic susceptibility reflect the exchange and g-factor anisotropy with J_z/J_x,y < 1 and g_z/g_x,y > 1, respectively. The exchange anisotropy and Dzyaloshinskii-Moriya interaction are responsible for the main broadening mechanism at higher temperatures while spin-diffusion effects prevail at helium temperatures. The ratio of the uniform susceptibilities calculated along the three crystal directions suggests an easy-axis anisotropy with the a axis as the magnetic easy axis. Its impact on the physical properties of the title compound is discussed.