Infrared and magnetic characterization of the multiferroic Bi2FeCrO6 thin films in a broad temperature range

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Infrared reflectance spectra of an epitaxial Bi2FeCrO6 thin film prepared by pulsed laser deposition on LaAlO3 substrate were recorded between 10 and 900 K. No evidence for a phase transition to the paraelectric phase was observed, but some phonon anomalies were revealed near 600 K. Most of the polar modes exhibit only a gradual softening, which results in a continuous increase of the static permittivity on heating. It indicates that the ferroelectric phase transition should occur somewhere above 900 K. Magnetic measurements performed up to 1000 K, revealed a possible magnetic phase transition between 600 and 800 K, but the exact critical temperature cannot be determined due to a strong diamagnetic signal from the substrate. Nevertheless, our experimental data show that the B-site ordered Bi2FeCrO6 is one of the rare high-temperature multiferroics.