Preparation and magnetic properties of Bi m + 1 Fe m − 3 Ti 3O 3 m + 3 thin films with magnetic order above room temperature

Abstract

Thin films of Bi m + 1 Fe m − 3 Ti 3O 3 m + 3 (BFTO) with m ≦ 9 have been successfully grown on (100) SrTiO 3 by chemical solution deposition. These films had the c axis normal to the film plane. The conversion electron Mössbauer spectoroscopy (CEMS) showed that the spectra of BFTO thin films exhibit an asymmetric quadrupole doublet for m = 8 at 300 K, indicative of being paramagnetic, while, for m = 9, clearly show six hyperfine lines indicating presence of magnetic order at 300 K. From the intensity ratio of asymmetric peaks, the polarization axis of BFTO films with m ≥ 8 was deduced to be likely along <101> of the perovskite-like unit. On the other hand, it was found from the spectral fitting that the BFTO thin film with m = 9 has the Néel temperature around 310 K and the spin axis making an angle of about 60° to the c-axis. These indicate that the BFTO ( m = 9) thin film is a promising candidate for room-temperature multiferroics.