Multiferroic BaTiO ₃ -CoFe ₂ O ₄ Nanostructures

Abstract

We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The films are epitaxial in-plane as well as out-of-plane with self-assembled hexagonal arrays of CoFe2O4 nanopillars embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and average spacing of 20 to 30 nanometers. Temperature-dependent magnetic measurements illustrate the coupling between the two order parameters, which is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show that the magnetoelectric coupling in such a nanostructure can be understood on the basis of the strong elastic interactions between the two phases.

Multiferroic nanocomposite fabrication via liquid phase using anodic alumina template

“…The saturation magnetization and coercivity evaluated from the magnetic hysteresis loops in Figure 6(a) were about 150 emu cm −3 (normalized to the volume fraction of CoFe 2 O 4 , ~ 20%) and 350 Oe, respectively, regardless of the orientation of the applied magnetic field. In comparison with similar reports [10,16,17], the out of plane coercivity of our sample is relatively small. This behavior can be explained by the following reasons:

the anisotropy is intrinsically small because the CFO nanotubes are short (length: ~250 nm, diameter: ~500 nm)

diffusion or rearrangement of atoms would occur at the interface of CFO and BTO, resulting in the deterioration of the magnetic properties of CFO

the vicinity of superparamagnetic limit should also be considered in our case because the walls of CFO nanotubes are very thin.

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“…These nanocomposites have the potential for applications in a variety of multifunctional devices, such as data storage media, in which magnetization can be reversed by applying an electric field (or vice versa), and microwave frequency transducers where the magneto-electric coupling constant depends on the frequency of applied alternating magnetic field [2–5]. Although several attempts for fabricating bulk-type multiferroic nanocomposites, by ceramic sintering and hot molding for example, have been reported so far [6,7], much more studies on fabrication of film-type nanocomposites by sol-gel process [8,9] and pulsed laser deposition (PLD) [10–13] have been recently published.…”

“…In order to achieve better properties, especially strong magneto-electric coupling, Zheng et al [10] demonstrated the advantage of a nanocomposite structure in which ferro/ferrimagnetic nanopillars are embedded in a ferroelectric matrix. They employed CFO and BaTiO 3 (BTO) as ferrimagnet and ferroelectric, respectively, and fabricated the nanocomposite on a SrTiO 3 (001) (STO) substrate by PLD from a single Ba-Ti-Co-Fe-oxide target via self-assembly.…”

Nanoscale Artificial Plasmonic Lattice in Self‐Assembled Vertically Aligned Nitride–Metal Hybrid Metamaterials

“…Compared to the extensively studied oxide–oxide VAN34, 35, 36, 37, 38 and recently reported metal–oxide VAN,26, 39 the nitride–metal VAN exhibits surprisingly ordered Au nanopillars, forming the APL hybrid systems. The growth of the APL hybrid structure is dominated by the different growth mechanisms of the metal and nitride in the systems.…”

“…Most of the VAN structures have been demonstrated in oxide–oxide systems,34, 35, 36, 37, 38 because of the excellent growth compatibility between the oxide–oxide systems. The growth of nitride–metal plasmonic lattice structures posed significant difficulties due to the large difference in growth kinetics of the two phases, i.e., a metal and a nitride in this case.…”