Structural and magnetoelectric properties of MFe 2 O 4 ?PZT (M?=?Ni,Co) and La x (Ca,Sr) 1-x MnO 3 ?PZT multilayer composites

Abstract

Thick film layered magnetoelectric composites consisting of ferromagnetic and ferroelectric phases have been synthesized with nickel ferrite (NFO), cobalt ferrite (CFO), La 0.7 Sr 0.3 MnO 3 (LSMO), or La 0.7 Ca 0.3 MnO 3 (LCMO) and lead zirconate titanate (PZT). Structural, magnetic and ferromagnetic resonance characterization shows evidence for defect free ferrites, but deterioration of manganite parameters. The resistivity and dielectric constants are smaller than expected values. The magnetoelectric effect (ME) is stronger in ferrite-PZT than in manganite-PZT. The ME voltage coefficient α E at room temperature is the highest in NFO-PZT and the smallest for LCMO-PZT. The transverse ME effect is an order of magnitude stronger than the longitudinal effect. Multilayer composites consisting of alternative layers of magnetostrictive and piezoelectric materials are observed to show a strong magnetoelectric (ME) effect and are of interest for studies on ME interactions and for potential use in devices [1][2][3][4][5]. Such structures when placed in an external ac magnetic field δH undergo deformation of the magnetic layer due to magnetostriction, resulting in an electrical polarization of the dielectric layer due to piezoelectric effect [6,7]. The ac electrical field δE produced in the structure is a "productproperty" and is proportional to the piezomagnetic and piezoelectric coefficients of the constituent phases [8]. The magnetoelectric voltage coefficient α E = δE/δH for such composites is in the range 50-5000 mV/Oe cm, depending on the nature and volume of the magnetic and piezoelectric phases [1][2][3][4]6,7]. These values far exceed the ME coefficient of 20 mV/Oe cm for Cr 2 O 3, the best single phase ME material [9].Theoretical models for a bilayer with parameters of nickel or cobalt ferrite and lead zirconate titanate predict coefficients as high as 1.5 V/Oe cm [7]. Although our studies reveal strong ME interactions in nickel ferrite -PZT samples, systems such as cobalt ferrite-PZT show a weak coupling [10]. The reason could be deterioration of physical properties of individual layers and poor mechanical coupling between the two phases due to defects at the interface formed during the sample processing [3,4,6]. A detailed and comprehensive investigation of structural, electrical and magnetic properties of the structures is important to elucidate the cause of magnetoelectric coefficient limitations.This report details the fabrication and characterization of multilayer thick film structures consisting of piezoelectric (lead zirconate titanate) and ferromagnetic (nickel ferrite, cobalt ferrite, and lanthanum-strontium or calcium manganite) phases. The choice of materials for the structures is due to the following reasons. All the materials, except the manganites, have ferromagnetic or ferroelectric phase transition temperatures well above the room temperature. Piezoelectric lead zirconate titanate (PZT) has high dielectric permeability and high piezoelectric coupling constants. Both nickel and cobalt fer...

Emerging Multiferroic Memories

“…In the 1990s theoretical calculations showed possible strong magnetoelectric coupling in a multilayer (2-2) configuration; an ideal structure to be examine by the burgeoning field of complex oxide thin-film growth [217]. In this spirit, researchers experimentally tested a number of materials in a laminate thick-film geometry, including ferroelectrics such as Pb(Zr x ,Ti 1−x )O 3 [218][219][220][221][222][223] [222], and others. These experiments showed great promise and magnetoelectric voltage coefficients up to ΔE/ΔH = 4,680 mV/ cm Oe have been observed.…”

Microstructure–property relationship in magnetoelectric bulk composites

“…Under the influence of externally applied magnetic field, NCFO domains are deformed in the magnetization direction, due to which the growth in the domains both with favorable orientation and domain rotation contributes to the magnetostriction effect [23].…”

“…Numerous groups have extensively studied on varies aspects of single phase ME materials [3][4][5][6] as well as bulk [7][8][9][10][11][12][13][14][15][16][17][18] and layered [19][20][21][22][23] composites, because of the simplicity of synthesis in using conventional ceramic processing. The single phase materials have not found much technological applications due to the fact that they mostly exhibit a very weak ME effect and most of them have Neél or Curie temperature far below room temperature.…”

Sandwich magnetoelectric composites of polyvinylidene fluoride, Tb-Dy-Fe alloy, and lead zirconate titanate

“…Mzumder [6] prepared a series of ME composites in the BaO-TiO-FeO-CoO quaternary oxide system by solid-state route, but the ME voltage coefficient was rather weak at room temperature. Srinivasan [7] synthesized thick-film layered magnetoelectric composites consisting of ferromagnetic and ferroelectric phase with nickel ferrite (NFO), cobalt ferrite, La 0.7 Sr 0.3 MnO 3 (LSMO), or La 0.7 Ca 0.3 MnO 3 (LCMO) and lead zirconate titanate (PZT) by the doctor-blade technique. Most recently, multiferroic composites [8] , such as ferrite/piezoelectric ceramics(Terfenol-D/PZT) have been found to exhibit high ME sensitivity, but the Terfenol-D/PZT cermet is very brittle and it is a challenge to prepare the Terfenol-D/PZT composites by a conventional sintering method.…”