Abstract
Porosity dependence of magnetoelectric (ME) parameters has been investigated in ferrite-piezoelectric bulk composites. Studies were performed on modified nickel ferrite-lead zirconate titanate. The modification involved departure from stoichiometry and the addition of cobalt oxide to the ferrite that resulted in orders of magnitude increase in the resistivity and an enhancement in the strength of ME voltage coefficient. Samples with porosity ranging from 5% to 40% were prepared. Data on low-frequency ME voltage coefficient revealed a 60%–70% decrease as the porosity was increased from 5% to 40%. The porosity dependence was even stronger for ME coupling at electromechanical resonance: a 96% reduction in the ME voltage coefficient when was increased from 5% to 40%. A model that considers the influence of porosity on ME interactions has been developed. The composite is assumed to consist of piezoelectric, magnetostrictive, and void (pores) subsystems. We solved combined elastostatic, electrostatic, and magnetostatic equations to obtain effective composite parameters (piezoelectric coupling, magnetostriction factors, compliances, ME coefficients). Expressions for porosity dependence of ME voltage coefficients have been obtained for low frequencies and at electromechanical resonance. The calculated ME coefficients are in very good agreement with the data.
1 More- Received 16 November 2006
DOI:https://doi.org/10.1103/PhysRevB.75.174422
©2007 American Physical Society