Multiferroic effects in MFe 2 O 4 /BaTiO 3 (M = Mn, Co, Ni, Zn) nanocomposites

Abstract

An increasing demand in realizing ultra-fast, compact and ultra-low power spintronic devices has impelled the creation of novel multiferroic heterostructures which enable voltage control of magnetism and vice-versa. For this, we have reported multiferroic properties of M(=Mn, Co, Ni, Zn)Fe2O4/BaTiO3 (MFO/BTO) nanocomposite. The MFO/BTO thin films were prepared by metallo-organic decomposition method. The MFO/BTO nanocomposite stoichiometric ratio has been analyzed with X-ray fluorescence elemental analysis. X-ray diffraction reveals the formation of both spinel MFO and perovskite BTO phases with crystallite size lies in the range of 25–137 nm. The lattice strain observed in MFO/BTO nanocomposite is due to tetragonal distortion of BTO unit cell and lattice mismatch with ferrite MFe2O4. The crystallite size is also depicted with atomic force microscopy. The observed ferromagnetism of MFO/BTO nanocomposite is highly influenced by inversion degree of MFO ferrite and oxygen vacancies formation. All MFO/BTO nanocomposites have well saturated ferroelectric hysteresis polarization. This has been discussed based on lattice strain, leakage current and the degree of lattice mismatch. The chemical valence states of Fe and O and their influence on the magnetic and ferroelectric properties have been analyzed with X-ray photoelectron spectroscopy. The capacitance versus bias voltage characteristics under the influence of applied dc magnetic field indicates ferroelectric behavior and the presence of magneto-electric/dielectric effects. The dielectric permittivity reduces with applied dc magnetic field which is responsible for negative magnetodielectric effect. The higher longitudinal magnetoelectric coupling coefficient is obtained in M(=Co, Ni, Zn)FO/BTO nanocomposite which is correlated with piezoelectric coefficient, d33 value measurement.