Structural,magnetic and dielectric properties of the novel magnetic spinel compounds ZnCoSnO4 and ZnCoTiO4

The transparent semiconductor Zn₂SnO₄ with cubic spinel structure and the isostructural Zn₂TiO₄ have been magnetically doped with Co²⁺. ZnCoSnO₄ and ZnCoTiO₄ exhibit ferrimagnetism below T_N ≈ 13?K and T_N ≈ 17?K. Ferrimagnetic moments are evident in M vs H curves below T_N by small hysteresis. Fits to strictly linear Curie-Weiss plots above T_N give μ_eff ≈ 4.86 μ_B and ≈4.91 μ_B for ZnCoSnO₄ and ZnCoTiO₄, above theoretical predictions. Impedance spectroscopy data from sintered ceramic can be fitted with a standard equivalent circuit model based on two RC elements for bulk and GB areas. The relative dielectric permittivity of the bulk is ≈20 and ≈30 for Zn₂SnO₄ and Zn₂TiO₄. The semiconducting ZnCoSnO₄ and ZnCoTiO₄ceramics exhibit bulk resistivity of ≈1 10⁶?Ω?cm and ≈1 10⁵?Ω?cm at 560?K (287?°C), and bulk activation energies of E_A ≈ 1.2?eV and 1.1?eV.