Equivalent Magnetic Noise in Magnetoelectric Laminates Comprising Bidomain LiNbO₃Crystals

Abstract

The anisotropic direct magnetoelectric (ME) properties of bilayered composites comprising magnetostrictive metglas foils and single-crystalline piezoelectric bidomain plates of 127°Y-cut LiNbO (LNO) have been studied theoretically and experimentally. The LNO plates possessed an engineered ferroelectric macrobidomain structure with opposite spontaneous polarization vectors. Impedance, ME effect, and equivalent magnetic noise density (EMND) measurements have been performed under quasi-static and resonant conditions. Whereas the quasi-static ME effect was only two times stronger in the bidomain samples compared to their unidomain and bonded bimorph counterparts, in the bending resonance mode, the effect was up to one order of magnitude stronger: ME coefficients of up to 578 V/( [Formula: see text]) were obtained at ca. 30 kHz under resonance using 0.5-mm-thick crystals. EMND measurements yielded values down to 153 pT/Hz at 1 kHz and 524 fT/Hz under resonant conditions. A further optimization of the fabrication techniques, laminate geometry, and detection circuit is expected to allow reducing these values down to at least 10 pT/Hz and 250 fT/Hz , respectively, and the resonance frequency by at least two orders of magnitude. Such systems may thus find use in simple and sensitive, passive and stable, low frequency and high-temperature vector magnetic field sensors.

Magnetoelectric Effect in the Bidomain Lithium Niobate/Nickel/Metglas Gradient Structure

“…To improve these parameters and to create ME structures for low‐frequency magnetic field applications, different strategies have been proposed. ME samples comprising a bimorph or bidomain structure in the piezoelectric component exhibited low‐frequency bending vibrations and a high sensitivity to magnetic field at the respective resonance frequency . The developed self‐biased ME structures in the form of graded ME laminates were based on PZT/Ni/metglas multilayers and (antiferromagnetic‐ferromagnetic)‐ferroelectric exchange‐biased ME composites .…”

Magnetoelectric metglas/bidomain y + 140°-cut lithium niobate composite for sensing fT magnetic fields

“…The measured impedance spectra of the thin-bar ME metglas / bidomain y+140º-cut LNC composite and of the PE bidomain y+140 o -cut LNC crystal alone operating in a free vibrating regime are shown in Figure 3(a). Superimposed are the calculated results obtained using a simple unidimensional ME model [18,19]. The resonance and antiresonance peaks are associated with lowfrequency bending electromechanical modes (EMR).…”

“…Despite their outstanding PE characteristics, these materials have a number of drawbacks, such as a low Curie temperature, considerable mechanoelectric hysteresis, creep (time delay and saturation between mechanical deformation and electric signal), nonlinear behavior, strong dependence of the properties on the temperature, as well as large dielectric losses. One possible approach to improve these parameters is to use lead-free PE single crystals such as lithium a) Correspondence should be addressed to a.turutin@misis.ru niobate with high voltage piezoelectric coefficients (g), low permittivity and very low mechanical and dielectric losses [16][17][18][19][20][21]. Furthermore, asymmetric bi-layered systems with bimorph PEs, containing two oppositely poled layers along the thickness direction, are able to generate large voltages under a low-frequency bending deformation and partially cancel both extrinsic vibrational and thermal noises [8,22].…”

“…Furthermore, some new promising techniques have been developed to directly engineer two ferroelectric domains with antiparallel spontaneous polarization vectors in a single crystal plate (bidomain) [23,24]. In a previous studies we proposed the use of square or long bar metglas / PE bi-layered composites with y+128°-cut LNC single-crystal "head-to-head" (H-H) and "tail-to-tail" (T-T) bidomains in sensitive magnetic field sensors [18,19].…”

“…Figure 4(a) shows the result of the quasi-static measurement of the transversal ME coefficient as a function of the applied in-plane bias field. Using a low-frequency model [18,19], the maximum expected quasi-static ME coefficient of |α E31 | = 5.4 V•(cm•Oe) -1 was calculated. The maximum measured quasi-static ME coefficient was as large as |α E31 | = 1.9 V•(cm•Oe) -1 .…”