Abstract:
The recent quest for improved functional materials like high permittivity dielectrics and/or
multiferroics has triggered an intense wave of research. Many materials have been checked for their
dielectric permittivity or their polarization state. In this report, we call for caution when samples are
simultaneously displaying an insulating behavior and a defect-related conductivity. Many oxides
containing mixed valent cations or oxygen vacancies fall into this category. In such cases, most of
the standard experiments may result in an effective high dielectric permittivity, which may not be
related to ferroelectric polarization. Here we list a few examples of possible discrepancies between
measured parameters and their expected microscopic origin.
