Anisotropy of Dielectric Dispersion in ErFe₂O₄ Single Crystal

Dielectric dispersion was observed in a single crystal with the composition of ErFe₂O_3.95 below magnetic transition temperature. It is characterized by a large dielectric constant of the order of 10⁴, and a Debye-type frequency dependence like in the poly crystalline samples of the same substance which we reported in a previous paper. Large anisotropy exists in the strength ε_s − ε_∞ and the characteristic relaxation frequency of the dispersion. The strength is higher within the c-plane than along the c-axis, while the characteristic frequency is much larger along the c-axis than within the c-plane. The dielectric dispersion in the polycrystalline sample cannot be explained by a simple average of the single crystal results. The observed dispersion is qualitatively discussed with a model of domain wall motion on an assumption that ErFe₂O₄ is a polar crystal.