Novel layered Bi ₃ MoM _T O ₉ (M _T = Mn, Fe, Co and Ni) thin films with tunable multifunctionalities

Bi3MoMTO9 (BMoMTO; MT, transition metals of Mn, Fe, Co and Ni) thin films with a layered supercell structure have been deposited on LaAlO3 (001) substrates by pulsed laser deposition. Microstructural analysis suggests that pillar-like domains with higher transition metal concentration (e.g., Mn, Fe, Co and Ni) are embedded in the Mo-rich matrix with layered supercell structures. The layered supercell structure of the BMoMTO thin films accounts for the anisotropic multifunctionalities such as the magnetic easy axis along the in-plane direction, and the anisotropic optical properties. Ferroelectricity and ferromagnetism have been demonstrated in the thin films at room temperature, which confirms the multiferroic nature of the system. By varying the transition metal MT in the film, the band gaps of the BMoMTO films can be effectively tuned from 2.44 eV to 2.82 eV, while the out-of-plane dielectric constant of the thin films also varies. The newly discovered layered nanocomposite systems present their potential in ferroelectrics, multiferroics and non-linear optics.