EPR Studies of Phase Transition and Jahn-Teller (JT) Effect of Copper II ion in Cadnium Amonium Sulphate Hexahydrate [Cu2+:Cd2(NH4)2(SO4)3.6H2O] Spectra in the Temperature Range 300-15 K

In this paper, EPR study of the spectra of Cu2+ in Cadnium Amonium Sulphate Hexahydrate (Cd2 (NH4) 2 (SO4) 3.6H2O) single crystals has been carried out in the temperature range 300-15 K. The spin Hamiltonian parameters of Cu2+ in this system were determined at different temperatures. The results show that this system exhibits JT effect and that the anisotropy in the g-factor and hyperfine tensor components decrease with increasing temperature similar to several known JT systems except g_- and g are different. This difference may be attributed to differences in the structural configurations of neighbouring ligands surrounding the paramagnetic Cu2+ in CASH and other related systems. It has been shown that the Cu-H2O bond lengths in the three directions in many Tuttons salts are not equal while in known static JT systems they are equal. Consequently, we conclude that it is possible the Cu-H2O bond lengths in CASH are different in the three directions which may be responsible for the observed differences in the g-values. We recommend that further x-ray and EPR or other related techniques be carried out to confirm the authenticity of the difference in Cu-H2O bond lengths in this system.