Modeling, simulation and synthesis of multiferroic magnetoelectric CoFe₂O₄/BaTiO₃ composite nanoparticles

Highlights

• Optical properties of CoFe₂O₄/BaTiO₃ nanoparticles were simulated using finite element analysis and quantum mechanical method.

• CoFe₂O₄/BaTiO₃ nanoparticles were synthesized and optical absorption measured utilizing UV-Visible spectroscopy.

• Characterization of CoFe₂O₄/BaTiO₃ nanoparticles was acquired using X-ray diffraction and transmission electron microscopy.

Abstract

Optical properties of cobalt ferrite (CoFe₂O₄)/barium titanate (BaTiO₃) nanoparticles are modeled and simulated utilizing density functional theory (DFT) and finite element analysis (FEA) intended for various particle sizes. The simulated absorption maxima of electronic excitations is red-shifted from 259.51 nm to 315.27 nm employing quantum mechanical approach and from 260 nm to 280 nm using finite element analysis, corresponding to enlarging particle sizes from 8 nm to 50 nm. The measured absorption maxima corresponded well to the simulated results and red-shifted to longer wavelengths from 302.02 nm to 321.28 nm accompanied by an increment in particle sizes from 30 nm to 50 nm. The FEA simulated, DFT simulated and experimentally extracted optical band gap energies were as well obtained and compared. Additionally, the ferromagnetic behavior of the CoFe₂O₄/BaTiO₃ nanoparticles was investigated.

Introduction

Multiferroic magnetoelectric (ME) composites are important and have attracted much attention due to their interesting new physics and potentials for exploring novel multifunctional devices [1]. These materials possess significant role in the electronic, magnetic and optical properties. Multiferroic magnetoelectric materials are used in many industrial applications, such as sensors, read heads, nonvolatile memory elements, nano-electronics and memories based on giant magnetoresistive effects [[2], [3], [4], [5]].

Among multiferroic magnetoelectric (ME) nanocomposites, cobalt ferrite (CoFe₂O₄)/barium titanate (BaTiO₃) nanoparticles have an important advantage due to the spinodal decomposition of this binary system, which prevents reaction between the constituents during high-temperature processing [6,7]. They have been extensively used for numerous applications, such as electro-magnetic interference filters, capacitors, transducers, integral chip inductors [[8], [9], [10]], spintronics, memory, and sensors [[11], [12], [13], [14]].

Various fabrication methods such as wet chemical synthesis [[15], [16], [17]], co-precipitation [18,19], thermal decomposition, hydro/solvo thermal synthesis, sol-gel method [16,20], microemulsion, combined hydrothermal and annealing processes [21], ball milling method [8], etc. have been reported for preparing CoFe₂O₄/BaTiO₃ nanoparticles.

The optical and magnetic properties of multiferroic magnetoelectric (ME) nanocomposites are currently of considerable interest, due to their wide applications in sensors, capacitors, transducers and memory. Among multiferroic magnetoelectric (ME) nanoparticles, cobalt ferrite (CoFe₂O₄)/barium titanate (BaTiO₃) nanoparticles have been substantially studied due to their fascinating optical and magnetic properties and quantum confinement effect. The optical absorption of cobalt ferrite (CoFe₂O₄)/barium titanate (BaTiO₃) nanoparticles is affiliated to electronic structure in terms of an inter-band electronic excitation from the valence band to the conduction band. The optical properties of the CoFe₂O₄/BaTiO₃ nanoparticles can be precisely tuned by changing the core size, shell thickness as well as the core and shell shapes. Moreover, it is well recorded that ferroelectric properties of BaTiO₃ and ferromagnetic properties of CoFe₂O₄ depend on particle size [6,22,23]. Correspondingly, one should anticipate a size impact on the magnetoelectric coupling in the composites.

In this research, we discuss the optical properties of cobalt ferrite (CoFe₂O₄)/barium titanate (BaTiO₃) nanoparticles of various sizes and compare the predicted properties based on quantum mechanical principles using density functional theory (DFT) with the experimentally observed results, assisted via the finite element simulations using COMSOL Multiphysics. Moreover, we investigated the ferromagnetic behavior of the CoFe₂O₄/BaTiO₃ nanoparticles.