Papers by Keyword: Magnetoelectric Effect

Abstract: Three phase composites that consists of piezoelectric and piezomagnetic fibers embedded inan elastic matrix phase exhibits new product properties such as magnetoelectric effect, pyroelectric andpyromagnetic effect, which are absent in individual phases. In this work, simple analytical expressionsare developed based on strength of materials approach to find these effective coupling coefficients. In amicro scale rectangular representative volume element (RVE) of a layered type three phase composite,series connectivity is assumed between fiber and matrix layers along transverse direction and parallelconnectivity is assumed along longitudinal direction. The analytical model is validated with otherhomogenisation methods and effective property variation of BaTiO₃-CoFe₂O₄-Epoxy composite andLiNbO₃-CoFe₂O₄- Epoxy composite are discussed.

Abstract: In the last decade, considerable attention has been focused on the search of new multiferroic materials and the ways of improvement of their magnetoelectric properties. In this short review, we survey the progress in study of multiferroics focusing the high temperature multiferroic bismuth ferrite and rare earth iron garnets. We discuss the recent results of investigation of domain walls in multiferroics, concentrating the most important magnetoelectric manifestations (electric polarization and magnetization), and the pinning effect appearing as clamping of ferroelectric and magnetic domain walls.

Abstract: Domain walls in iron garnet films demonstrate magnetoelectric properties that manifest themselves as a displacement induced by inhomogeneous electric field. In this paper the results of the study of electric field induced domain wall dynamics and its dependence on external magnetic field are presented. The measured velocity of the electrically induced domain wall motion increased by an order with the magnetic field applied perpendicular to the domain wall plane. The numerical simulation shows that the observed behaviour of the domain wall can be explained by magnetic field induced modification of its internal micromagnetic structure and enhancement of the electric polarization associated with the wall.

Abstract: Multiferroic films of BiFeO₃, (BiLa)FeO₃ and (BiNd)FeO₃ with various concentration of ions of Bi, La and Nd in dodecahedral sublattice utilising were fabricated on monocrystalline substrates of (001) SrTiO₃, (100) MgO and (100) Al₂O₃ by a number of technological methods: rf sputtering, vacuum laser ablation and metal-organic chemical vapor deposition (MOCVD). The film thickness varied in the range of 30-300 nm. The magnetic and magnetoelectric properties of the obtained films were investigated. The saturation magnetization of BiFeO₃ was about 9 emu/cm³ which is typical of strained films of this composition. Doping BiFeO₃ films by rear earth ions La (Nd) increases both the magnetisation saturation and Neel temperature, as well as magnetoelectric effects, which is explained by increase in magnetic crystal anisotropy and suppression of spatially modulated magnetic structure. It was demonstrated that the corona discharge treatment resulted in a substantial growth of the magnetisation saturation up to 35% whereas the changes in the Neel temperature were not noticible. This is explained by the induced electret state and giant magnetoelectric effect.

Abstract: Temperature characteristics of resonant magnetoelectric effect in bilayer structures consisting of langatate, lead zirconate titanate, nickel, and amorphous ferromagnetic Metglas layers have been investigated. The measurements were performed in the temperature range of 150-400 K. The influence of the ferromagnetic and piezoelectric layer’s parameters on the temperature dependence of resonant frequency and magnetoelectric coefficient α_E has been demonstrated. The results can be used to develop magnetoelectric magnetic field sensors.

Abstract: The present paper focuses on the magnetoelectric coupling in dimensionally graded ferrite-piezoelectric bilayers in the electromechanical resonance region. Using the bilayer as a transducer which converts the ac magnetic field into an ac electric field shows that the transmission coefficient equals approximately -83 dB for zero bias magnetic field and -44 dB for bias field of 340 Oe. Thus, applying the DC field enables one to obtain the transmission coefficient variation range of 39 dB for the investigated structure. The phenomenon is of importance for the realization of multifunctional magnetoelectric devices including sensors and transducers operating at microwave frequencies.

Abstract: This manuscript is devoted to the magnetoelectric coupling in a dimensionally graded magnetostrictive-piezoelectric structure in the electromechanical resonance region. Theoretical frequency dependence of ME voltage coefficient is obtained. Theoretical estimates for the layered structure of lead zirconate-titanate and single-crystal Zn_0,3Ni_0,7Fe₂O₄ are in satisfactory agreement with data. The obtained results are expected to facilitate observation of enhanced ME coupling at overlapping of electromechanical and magnetic resonance due to energy transfer between spin waves and phonons.

Abstract: To investigate the mechanism of self-bias magnetoelectric effect in magnetoelectric composite materials, a synchronous characterization technique was developed to characterize the magnetoelectric effect, the magnetostrictive effect, and the magnetic hysteresis loop by one-time test. The results of a magnetoelectric composite consisting of hybrid ferromagnetic phases showed that the obvious magnetoelectric hysteresis behavior was found with significant self-bias magnetoelectric effect. In addition, after demagnetizing, the residual magnetic polarization became zero and the magnetoelectric effect disappeared at the same time. Since the ferromagnetic phases were separated from each other, the mechanism of self-bias magnetoelectric effect mainly resulted from static magnetic coupling instead of build-in magnetic field. It was concluded that the synchronous characterizing technique was quite helpful when analyzing the mechanism of magnetoelectric behavior.

Abstract: FeGa/PZT/FeGa magnetoelectric device was prepared and the ME effect examined. FeGa alloys was made by different processing method. The results showed that the domains and texturing of FeGa had a great impact on both magnetic and ME performance. The permeability and d₃₃ (the differential of magnetostrictive coefficient) of FeGa differed with processing. It was found that FeGa rolled sheets had good toughness, d₃₃ could reach 2.7 ppm/Oe, and magnetic permeability reached 180 H/m. The device made of FeGa rolled sheets also had a large output (18 V/cm Oe) and low bias field (~ 96 Oe).

Abstract: By using a elastic mechanics model the transverse magnetoelectric voltage coefficient of magnetostrictive-piezoelectric bilayer is derived according to the constitutive equations. The transverse magnetoelectric coupling of nickel zinc ferrite-lead zirconate titanate (Ni_0.8Zn_0.2Fe₂O₄–Pb (Zr,Ti)O₃, NZFO-PZT) layered composites were calculated by using the corresponding material parameters of individual phases. NZFO samples have been synthesized with sol–gel technique. Layered composites NZFO-PZT and NZFO-PZT-NZFO have been fabricated by binding discs of NZFO and commercially available PZT, and the transverse magnetoelectric effect have been investigated. The peak value of transverse magnetoelectric voltage coefficient for NZFO-PZT-NZFO trilayer reaches 252.4 mV/cmOe under a bias magnetic field of about 320 Oe, which is about three times as large as that of NZFO-PZT bilayer. The interface coupling parameter of trilayer is significantly higher than that of bilayer.