Substrate induced strain effects on the multiferroism of BiMnO$_{3}$ thin films

BiMnO$_{3}$ is a single phase multiferroic material, which shows ferroelectricity and ferromagnetism at low temperature. However, it is difficult to grow BiMnO$_{3}$ either in bulk or thin film form, since it is metastable with substantial desorption of Bi ions at high growth temperature. Here we have used SrTiO$_{3}$ and SrLaGaO$_{4}$ substrates, which provide different degrees of compressive strain, to stabilize the BiMnO$_{3}$ phase and have introduced fast quenching after deposition in oxygen atmosphere to suppress re-evaporation of Bi-ions but retain film crystallinity. Surface morphology indicates island growth mode. X-ray diffraction (XRD) shows that the BiMnO$_{3}$ [111] is parallel with [001] SrTiO$_{3}$ and [001] SrLaGaO$_{4}$. XRD results confirm that the BiMnO$_{3}$ films on SrTiO$_{3 }$substrates are epitaxial, with in-plane alignment. The films have a magnetization of 1 $\mu _{B}$/Mn at 5 T and 10 K. We also observed ferroelectricity in our BiMnO$_{3}$ films. Based on these results, we will discuss the substrate induced strain effects on the multiferroic properties of BiMnO$_{3}$ thin films.