Multiferroic BaTiO3-CoFe2O4 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. Temperaturedependent

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.