Magnetoelectric perovskite-spinel bilayered nanocomposites synthesized by liquid-phase deposition

Highly uniform bilayered perovskite-spinel hybrid nanostructures were deposited on glass and LaNiO₃-buffered (100) silicon substrates at almost-ambient temperatures via the liquid-phase deposition (LPD) method. Field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) evidenced that the perovskite and spinel layers are constructed by arrays of densely packed nanoparticles with uniform sizes. The bilayered nanocomposites exhibit both piezoelectricity and ferrimagnetism at room temperature. The value of the static piezoelectric coefficient of the PbTiO ₃ (PTO) film was 14.1 pm/V, whereas the values of the saturation magnetization were 234.4 and 223.2 emu/cm³ for the PbTiO ₃-Co_0.32Fe2.68O4 (CFO) and PbTiO₃- Ni _0.66Fe_2.34O₄ (NFO), respectively. The coercivity of the nanocomposite decreased by 12.11% for the PTO-CFO, whereas, for the PTO-NFO, it increased by 20%, with respect to the coercivity values of the pristine ferrite films, which is the result of amagnetoelectric coupling between the two dissimilar layers in the nanocomposite. Additional evidence about a stress-induced magnetoelectric coupling in these bilayered structures was provided by Raman spectroscopy, which showed that, under a magnetic field, the vibrational modes of the nanocomposite are altered by the deformation of the top ferrite layer. In turn, this will generate a stress at the shared interface, thereby leading to a shift toward higher wavenumbers of the Raman bands of both the perovskite and spinel phases.