Dielectric Properties of the Charge Ordered Oxyborate Fe$_{2}$ OBO$_{3}$

In this work we present a detailed investigation of the dielectric properties of the oxyborate Fe$_{2}$ OBO$_{3}$ . This compound exhibits a high dielectric constant at room temperature $(\varepsilon^{\prime}_{\rm r} > 10^{3})$ for frequencies up to $10^{4}$ Hz. An impedance spectroscopy analysis of the data reveals an important extrinsic contribution to these high $\varepsilon^{\prime}_{\rm r}$ values. In order to eliminate the extrinsic contribution, we have sandwiched the sample in-between two mica layers, obtaining relatively high values of $\varepsilon^{\prime}_{\rm r}$ at room temperature for this kind of oxides $(\varepsilon^{\prime}_{\rm r} \sim 45)$. The temperature dependence of the remaining intrinsic contribution shows a jump, that at high frequencies occurs at the temperature at which a rearrangement of the charge-order pattern takes place and at low frequencies occurs at temperatures close to the onset of the antiferromagnetic long-range order. This suggests a certain coupling between the electronic, magnetic and dielectric properties in this compound.