tailieunhanh - FERROELECTRICS – PHYSICAL EFFECTS_2

Tham khảo sách 'ferroelectrics – physical effects_2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Part 3 Magnetoelectrics and Multiferroics 12 Magnetoelectric Multiferroic Composites M. I. Bichurin1 V. M. Petrov1 and -Novgorod State University 2Virginia Tech 1Russia 2USA 1. Introduction Magnetoelectric ME multiferroics are materials in which ferromagnetism and ferroelectricity occur simultaneously and coupling between the two is enabled. Applied magnetic field H gives rise to an induced polarization P which can be expressed in terms of magnetic field by the expression P aH where a is the ME-susceptibility tensor. Most of the known single-phase ME materials are known to show a weak ME coupling Fiebig 2005 Kita et al. 1988 Wang et al. 2003 Prellier et al. 2005 Cheong et al. 2007 . A composite of piezomagnetic and piezoelectric phases is expected to have relatively strong ME coupling. ME interaction in a composite manifests itself as inducing the electrical voltage across the sample in an applied ac magnetic field and arises due to combination of magnetostriction in magnetic phase and piezoelectricity in piezoelectric phase through mechanical coupling between the components Ryu et al. 2001 Nan et al. 2008 Dong et al. 2003 Cai et al. 2004 Srinivasan et al. 2002 . In last few years strong magneto-elastic and elasto-electric coupling has been achieved through optimization of material properties and proper design of transducer structures. Lead zirconate titanate PZT -ferrite and PZT-Terfenol-D are the most studied composites to-date Dong et al. 2005 Dong et al. 2006b Zheng et al. 2004a Zheng et al. 2004b . One of largest ME voltage coefficient of 500 Vcm-1Oe-1 was reported recently for a high permeability magnetostrictive piezofiber laminate Nan et al. 2005 Liu et al. 2005 . These developments have led to magnetoelectric structures that provide high sensitivity over a varying range of frequency and DC bias fields enabling the possibility of practical applications. In this paper we focus on four broad objectives. First we discuss detailed mathematical modeling