Dielectric response of the charge-ordered two-dimensional nickelate La1.5Sr0.5NiO4

We report the dielectric response of La1.5Sr0.5NiO4, a system that experiences charge ordering above room temperature (T-CO=480 K) and a rearrangement of its charge-order pattern in the temperature region 160-200 K. A careful analysis of the role of the electrical contacts used, sample thickness, and grain size on the experimental data allows us to determine that this material exhibits a high intrinsic dielectric constant. In addition, the temperature dependence of the dielectric constant, that shows a maximum in the region of the rearrangement of the charge-order pattern, points to a link between the two phenomena. (C) 2004 American Institute of Physics.