  The properties of epitaxial Bi2FeCrO6 thin films, recently synthesized by
pulsed laser deposition, have partially confirmed the theoretical predictions
(i.e. a magnetic moment of 2 muB per formula unit and a polarization of ~80
microC/cm2 at 0K). The existence of magnetic ordering at room temperature for
this material is an unexpected but very promising result that needs to be
further investigated. Since magnetism is assumed to arise from the exchange
interaction between the Fe and Cr cations, the magnetic behaviour is strongly
dependent on both their ordering and the distance between them. We present here
the successful synthesis of epitaxial Bi2FexCryO6 (BFCO x/y) films grown on
SrTiO3 substrates using dual crossed beam pulsed laser deposition. The crystal
structure of the films has different types of (111)-oriented superstructures
depending on the deposition conditions. The multiferroic character of BFCO
(x/y) films is proven by the presence of both ferroelectric and magnetic
hysteresis at room temperature. The oxidation state of Fe and Cr ions in the
films is shown to be 3+ only and the difference in macroscopic magnetization
with Fe/Cr ratio composition could only be due to ordering of the Cr3+ and Fe3+
cations therefore to the modification of the exchange interaction between them.
