Electrical and Magnetic Properties of Multiferroic $(1\hbox{-}{\rm x})\ {\hbox{BiFeO}}_{3}\hbox{-}{\rm x}\ {\hbox{CoFe}}_{2}{\hbox{O}}_{4}$ Nanocomposite Thin Films Derived by Sol-gel Process

Abstract

In the present work, multiferroic (1-x) BiFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -x (CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) ( x=0, 0.3, 0.5) nanocomposite thin films were prepared by sol-gel spin coating process. Structural, electrical and magnetic properties of nanocomposite thin films have been studied. X-ray diffraction study confirmed the co-existence of both perovskite BiFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BFO) and spinel CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CFO) phases. Atomic force microscopy shows CFO particles distributed in BFO matrix. These nanocomposite thin films exhibit both ferroelectric and ferromagnetic switching at room temperature. The magnetic and dielectric properties are improved by incorporation of CFO grains in matrix of BFO. The saturation magnetization (M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) increases as x varies from 0 to 0.5. For x=0.5, M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> is found as high as ~ 196 emu/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Coercivity is increased with CFO concentration and found maximum ( H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ~ 1.20 kOe) for x=0.50. This large increase in coercivity indicates strong magnetoelastic coupling. The dielectric constant of the films is increased from 240 (for x=0) to 370 (for x=0.5). All composite films show ferroelectric behavior, however the ferroelectric properties are found to decrease with incorporation of magnetic phase.