Electrical and magnetic properties of CuEu_2W_2O_(10) and Cu_3Eu_2W_4O_(18)

摘要

Magnetic susceptibility measurements showed both a weak response to magnetic field and a lack of the Curie-Weiss region for CuEu_2W_2O_(10) and Cu_3Eu_2W_4O_(18) tungstates characteristic for the multiplet widths comparable to thermal energy. Magnetization measurements displayed the linear temperature dependence with the lower magnetic moment for Cu_3Eu_2W_4O_(18) in comparison with CuEu_2W_2O_(10), indicating that the effect of the electric charges associated with the surrounding ligands can change the multiplet width of individual states. It is affecting the electrical properties of examined tungstates which reveal the insulating state and low relative permittivity ε_r ～ 29 in case of CuEu_2W_2O_(10) and the thermally activated p-type electrical conduction for Cu_3Eu_2W_4O_(18) with the activation energy of 1.11 eV and the large value of ε_r ～ 217 above the room temperature.