Analysis of multiferroic properties in BiMnO3 thin films

Abstract

Textured BiMnO3 [111] thin films on SrTiO3 (100) and Pt/TiO2/SiO2 substrates were grown via r.f. magnetron sputtering (13.56 MHz). The XRD spectra confirmed a monoclinic structure and high-quality textured films for the BiMnO3 films. The films grown on SrTiO3 (100) showed higher crystalline quality than those developed on Pt/TiO2/SiO2. Through optimized oxygen pressure of 5×10-2 mbar during the r.f. sputtering deposition, the crystalline orientation of the BiMnO3 film was improved with respect to the previously reported value of 2×10-1 mbar. The values of spontaneous polarization (Ps), remnant polarization (Pr), and coercive field (Fc) from ferroelectric hysteresis loops (P–E) at different temperatures were also obtained. Samples with higher crystalline order revealed better dielectric properties (high Ps and Pr values and a low Fc). For films on both types of substrates, the ferroelectric behavior was found to persist up to 400K. Measurements at higher temperatures were difficult to obtain given the increased conductivity of the films. Magnetic hysteresis loops from 5K to 120K were obtained for BiMnO3 films grown on SrTiO3 and Pt/TiO2/SiO2 substrates. The results suggested that the coexistence of the magnetic and electric phases persists up to 120K.