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

Abstract

The transparent semiconductor Zn₂SnO₄ with cubic spinel structure and the isostructural Zn₂Ti₄O have been magnetically doped with Co^(2++) ZnCoSnO₄ and ZnCoTiO₄ exhibit ferrimagnetism below TN ≈ 13 K and TN ≈ 17 K. Ferrimagnetic moments are evident in M vs H curves below TN by small hysteresis. Fits to strictly linear Curie-Weiss plots above TN give µ_(eff) ≈ to 4.86 µ(B) and a ≈ to 4.91 µB 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 ≈ to 30 for Zn₂SnO₄ and Zn₂TiO₄. The semiconducting ZnCoSn SnO₄ and ZnCoTiO₄ceramics exhibit bulk resistivity of ≈ to 1 10⁶Ω cm and ≈ to 1 10⁵ Ωcm at 560 K (287°C), and bulk activation energies of EA ≈ to 1.2 eV and 1.1 eV.