Dielectric Properties of the Charge Ordered Oxyborate Fe OBO

In this work we present a detailed investigation of the dielectric properties of the oxyborate Fe₂OBO₃ . This compound exhibits a high dielectric constant at room temperature (epsiv_r' > 10³) for frequencies up to 10⁴ Hz. An impedance spectroscopy analysis of the data reveals an important extrinsic contribution to these high epsiv_r' values. In order to eliminate the extrinsic contribution, we have sandwiched the sample in-between two mica layers, obtaining relatively high values of epsiv_r' at room temperature for this kind of oxides (epsiv_r' ~ 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.