Dielectric and magnetic permittivities of three new ceramic tungstates MPr₂W₂O₁₀ (M = Cd, Co, Mn)

Abstract

Broadband dielectric spectroscopy measurements revealed an anomalously large relative permittivity value (ε _r = 884) for MnPr₂W₂O₁₀, a smaller value (ε _r = 156) for CoPr₂W₂O₁₀ and the smallest value (ε _r = 22) for CdPr₂W₂O₁₀ at low frequency (ν = 0.1 Hz) and above room temperature in the insulating and paramagnetic state. Below 273 K, the relative permittivity (ε _r∼ 24) did not depend significantly on frequency for all the tungstates under study. Electrical resistivity, thermoelectric power, electron paramagnetic resonance, magnetic susceptibility and magnetization provided experimental evidence that the studies tungstates were paramagnetic insulators with low n-type conduction. Only in the case of MnPr₂W₂O₁₀ was a ferrimagnetic order below 45 K observed. These effects are discussed within the framework of Maxwell–Wagner polarization, chemical covalent bonds and porosity mechanism.

Keywords:

• electrical properties
• broadband dielectric spectroscopy
• magnetic oxides

Acknowledgements

This work was partly supported by Ministry of Scientific Research and Information Technology (Poland). The authors are very grateful to Professor D. Skrzypek from the Institute of Physics of the University of Silesia in Katowice for her helpful discussion.