Observation of saturated polarization and dielectric anomaly in magnetoelectric BiFeO3 thin films

Abstract

We report here synthesis of phase-pure magnetoelectric BiFeO3 thin films with controlled oxygen stoichiometry on Pt/TiO2/SiO2/Si substrate using pulsed-laser deposition technique. Saturated ferroelectric hysteresis loop has been observed in phase-pure and highly resistive BiFeO3 thin films. The dielectric response study of the films with temperature indicates an anomaly in dielectric constant ε(T), in the vicinity of Néel temperature (∼380 °C). This anomaly in ε(T) is explained as an influence of vanishing magnetic ordering on electric ordering of magnetoelectric BiFeO3 sample.

First-principles study of spontaneous polarization in multiferroicBiFeO3

“…Teague et al 13 initially reported a polarization along ͓111͔ of just 6.1 C/cm 2 ; although these authors state that their hysteresis loops were not saturated, their measurements were supported by more recent studies of both BiFeO 3 / BaTiO 3 alloy films 15 and pure BiFeO 3 polycrystalline films. 16 The small values are in sharp contrast with recent experiments on epitaxial thin film samples of BiFeO 3 , which were found to possess large polarizations. The first thin film measurements 8 yielded values of 50-90 C/cm 2 on ͑100͒ aligned substrates, increasing to 100 C/cm 2 for ͑111͒ orientations.…”

Preparation of La-doped BiFeO3 thin films with Fe2+ ions on Si substrates

“…This type of dielectric anomaly in simultaneous ferroelectrically and ferromagnetically ordered systems was predicted by the LandauDevonshire theory of phase transition as an influence of varying magnetic order on the electric order 25 26 We can also see that the anomalous temperature decreases with increasing frequency. In addition, such an anomaly of this kind was not found in BFO thin films for the reason that for BFO the anomalous temperature was reported above 300°C, 27 at which the dielectric loss was high for our films.…”

Magnetic and electrical properties of single-phase multiferroic BiFeO3

“…It was proposed 4 that the oxygen deficiency may lead to valence fluctuation of Fe ions 3+ to 2+ states͒ in BFO resulting in high conductivity. However, such a possibility was recently ruled out in samples synthesized by liquid-phase sintering 7 where sintering time for the heating, sintering, and cooling times were limited to seconds only.…”

“…However, there is tremendous success in the fabrication of heteroepitaxially constrained thin films of BFO which shows enhanced polarization with saturated hysteresis loop and ferromagnetic behavior at room temperature. 3,4 There are several reports 5,6 on the fabrication of BFO dispersed in BaTiO 3 matrix to restrict the second phase, leakage current, and low resistivity in the sample. Recently, single-phase BFO ceramic samples have been synthesized by rapid liquid-phase sintering technique.…”