Nonlinear Magnetoelectric Effect in Magnetically Disordered Relaxor Ferroelectrics

Abstract

The nonlinear magnetoelectric effect in a relaxor ferroelectric, which is randomly diluted by a (ferro)magnetic compound, is investigated on the basis of a phenomenological Landau-type free energy model. It is assumed that macroscopic electrostrictive and magnetostrictive deformations give rise to fourth-order magnetoelectric terms in the free energy functional. On a mesoscopic scale this implies that the local electric field inside a polar nanoregion (PNR), which is temperature dependent, is modified both by the applied electric field and magnetic field . The dielectric relaxation time is shown to obey a modified Vogel-Fulcher relation and diverges on a critical surface in the space.

Keywords:

• Magnetoelectric effect
• relaxor ferroelectrics and ferromagnetics
• Vogel-Fulcher relation

Acknowledgments

This work was supported by the Slovenian Research Agency through Research Programs P1-0044 and P1-0125, and by the European project MULTICERAL. We are grateful to James F. Scott for helpful suggestions and comments on the manuscript