To explore the novel thin film with multiferroicity at room temperature, the bismuth-layer-structured Bi5Fe0.5Co0.5Ti3O15 (BFCT) thin films were prepared using chemical solution deposition technique. The microstructure, electric, and magnetic properties were investigated in BFCT film. A defined hysteresis loop of the BFCT film was obtained with the remnant polarization (2Pr) ∼ 31.7 μC/cm2 at 1 kHz under the electric field 300 kV/cm. To exclude contribution of the leakage current to polarization, we studied the dependence of hysteresis loops on the measuring frequency in the range from 100 Hz to 2 kHz and made the positive-up-negative-down (PUND) measurements in BFCT thin film. Both the results indicate the intrinsic ferroelectric property, and the leakage current does not play a big role in BFCT film. Meanwhile, the ɛ-V curve can also support the natural ferroelectricity in the BFCT film. We also found that the BFCT film shows weak ferromagnetism with the saturated magnetization (Ms) ∼2.6 emu/cm3. Furthermore, the magneto-dielectric effect was observed with MDC ∼ 0.39% at the frequency 100 kHz. The origin of weak ferromagnetism and the magneto-dielectric effect was discussed.

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Thin films of Fe-containing the Aurivillius phase Bi5FeTi3O15 (BFTO) were successfully prepared by chemical solution deposition. The microstructure, ferroelectric behaviours, magnetic properties and the magneto-dielectric effect were investigated systematically at room temperature (RT). A definite hysteresis loop of the BFTO film was obtained with the remanent polarization (2P r) ∼ 43.3 µC cm−2 under an electric field of 300 kV cm−1. To exclude the contribution of the leakage current to polarization, we studied the frequency dependence of hysteresis loops in the BFTO thin film and made positive-up–negative-down measurements. These results indicated the intrinsic ferroelectricity in the present BFTO film and it was supported by the ε–V curve. Furthermore, a weak ferromagnetism with an in-plane saturated magnetization (M s) of ∼ 1.7 emu cm−3 was also observed in the BFTO film, which may have originated from the Fe2+–O–Fe3+ nanocluster and the F-centre exchange (FCE) mechanism. Therefore, the ferromagnetism could be considered as in nanoregions. More importantly, the magneto-dielectric effect was found with a magneto-dielectric coefficient of ∼−2.8% at a frequency of 100 kHz at RT. The probable origins of magnetic anisotropy and the magneto-dielectric effect were discussed. All these results demonstrated the RT multiferroic behaviour of the BFTO film.

Magnetic field induced dielectric relaxation in the strain glass state of Pr0.6Ca0.4MnO3Yb 3 Fe 5 O 12 ceramics with garnet structure were prepared employing the solid-state reaction method. The results reveal that the emergence of Fe 2þ ions greatly affects dielectric relaxation, magnetic relaxation, saturation magnetization, and magnetoelectric coupling, which was further confirmed by oxygen treatment. More interestingly, the magnetoelectric coefficient (a) reaches 28 ps m À1 at room temperature, which is among the largest values for present single-phase magnetoelectric materials.

The ferroelastic strain coupling in multiferroic heterostructures is explored aiming at novel physical effects and fascinating functionality. Ferroelastic domain walls in manganites induced by a stripe BiFeO3 template can modulate the electronic transfer and sufficiently block the magnetic ordering, creating a vast anisotropy. The findings suggest the great importance of ferroelastic strain engineering in material modifications.