Title: Improper multiferroicity and colossal dielectric constants in Bi$_{2}$CuO$_{4}$,
Abstract: The layered cuprate Bi$_{2}$CuO$_{4}$ is investigated using magnetic,
dielectric and pyroelectric measurements. This system is observed to be an
improper multiferroic, with a robust ferroelectric state being established near
the magnetic transition. Magnetic and dielectric measurements indicate the
presence of a region above the antiferromagnetic Neel temperature with
concomitant polar and magnetic short range order. Bi$_{2}$CuO$_{4}$ is also
seen to exhibit colossal dielectric constants at higher temperatures with
clearly distinguishable grain and grain boundary contributions, both of which
exhibit non-Debye relaxation.