Dielectric Relaxation and Hopping of Electrons in ErFe₂O₄

抄録

We report the frequency and the temperature dependence of the dielectric constant of polycrystalline ErFe₂O_4-δ with different degrees of oxygen deficiency δ . A large dielectric relaxation, with the order of magnitude of 10⁴ and nearly of the Debye type, is observed in the magnetically ordered states within the temperature and frequency ranges of 150, K to 290, K and 1, kHz to 3, MHz, respectively. The dispersion is larger in the sample with more oxygen deficiency. From the temperature dependence of the characteristic frequency, we conclude that the elementary process of the dispersion is related to electron hopping between Fe²⁺ and Fe³⁺ ions. A large value of the dielectric constant is consistent with the existence of spontaneous polarization in the magnetic phases of this oxide. We propose that the motion of the polarization domain boundaries is a determining factor of low-frequency dielectric constant.