Quasi-intrinsic magnetoelectric coupling in multiferroic nanocomposite thin films

Abstract

Intrinsic tendency of magnetoelectric (ME) coupling in a given multiferroic system is difficult to experimentally substantiate because it represents the degree of coupling between polarization and magnetization vectors in the absence of any probing field. To assess the degree of this intrinsic coupling in a multiferroic nanocomposite thin film, we have developed thermodynamic formalisms based on the Landau-Devonshire theory and applied these to a type of nanocomposite film in which ferromagnetic Co particles are uniformly dispersed in a ferroelectric ${\text{BaTiO}}_{3}$ (BTO) matrix. Analysis of the weak-field magnetic susceptibility and the magnetodielectric data indicates that the quasi-intrinsic ME effects which originate from the interfacial strain-mediated coupling of piezoelectricity and magnetostriction destabilize the BTO-Co composite film thermodynamically. Essentially the same conclusion was made on the quasi-intrinsic ME coupling of the ${\text{BTO-CoFe}}_{2}{\text{O}}_{4}$ nanopillar structure.