During the last few years, multiferroic materials as BiFeO3 (BFO) have received a great deal of attention due to their potential applications for magnetoelectric devices. At room temperature, the BFO is a single-phase magnetoelectric multiferroic with antiferromagnetic and ferroelectric ordering that exhibits a large spontaneous electric polarization. However, a novel ferromagnetic state coexisting with ferroelectric ordering at room temperature in (012)-oriented and strained BFO thin films grown using a sputtering technique on La0.7Sr0.3MnO3/SiO2/Si(100) has been reported, recently, by M.C. Ramírez-Camacho et. al. (Acta Materialia 128, 2017, 451-454). The aim of this theoretical work is to study the existence and stability of such ferromagnetic state in BFO when it grows epitaxial on (012)-oriented La0.67Sr0.33MnO3 (LSMO) substrate. The role of the structural parameters and the magnetic ordering of the LSMO constraining the new ferromagnetic configuration in the BFO structure and coexisting with the characteristic ferroelectric order, is evaluated. The calculations of the electronic, structural, optical, and magnetic properties of (012)-oriented LSMO and BFO films, and BFO/LSMO interface have been carried out within the Density Functional Theory + Hubbard U (DFT+U) formalism using the Quantum Espresso package. The spontaneous polarization of the BFO phase has been computed by means of the Modern Theory of Polarization. A comparative analysis with the experimental evidence is presented.
This work was partially supported by PAPIIT-DGAPA-UNAM Grants IN110315, IN105317 and CoNaCyT Grants Fronteras 2026, and Projs. 282778 and 280309. Thanks are due to A. G. Rodriguez for his technical assistance.