Giant zero-biased magnetoelectric coupling characteristics in flexible Metglas/poly(vinylidene fluoride) heterostructures

Abstract

Magnetoelectric (ME) effect have intrigued dramatic research interests in the past decades, owing to its potential applications in a large number of new multifunctional devices, including magnetic storage, energy harvesters, magnetic field sensors, transformers, and microwave devices, among other. [1] , [2] It exists in materials by different principles: through the elastic coupling between magnetostrictive and piezoelectric phases (in ME composites) or through the coupling of electric dipole and magnetic moment (in singlephase ME material). In general, ME single-phase materials are not suitable to be utilized in technological application, owing to their low ME response which typically occurs at low temperatures. Compared with single-phase ME materials, ME composites have exhibited commendable ME coupling characteristic at room temperature. Furthermore, among ME composites, laminates show the largest ME response, thus being the most suitable structure for industrial applications. However, in spite of laminated ME composites have shown high ME conversion coefficient and strong ME responses, the external dc bias magnetic field $(H_{dc})$ is indispensable due to the saturation magnetostrictive coefficient of magnetostrictive material can be obtain only under a high $H_{dc}$, which will improve production costs and increase technical difficulty in industrial production. To overcome these shortcomings, some researchers have focused on zero-biased ME composites. In particular, Mandal et al. have reported zero-bias ME coupling for samples of PZT and magnetization-graded ferromagnetic layers, the grading in the magnetization is achieved with the use of Ni and Metglas. [3] Chen et al. demonstrated that a multiferroic heterostructure consisting of piezoelectric ceramic PZT, giant magnetostrictive material Terfenol-D, and different thickness soft magnetic alloy FeCuNbSiB shows an enhancement in the ME coefficient at zero bias. [4] Although those works have investigated zero-biased ME response of the laminates, they require complicated synthesis process. Moreover, conventional ceramic based laminated ME composites consisting of piezoelectric ceramics (e.g., PZT and (PMN-PT)) are usually fragility, non-bendable, fatigue, and expensive, which do not meet the increasing industry demands in terms of flexibility, complicated shape, and cost, hindering them from being used in rapidly growing technological areas such as wearable devices. Bearing these in mind, in this paper, the flexible zero-biased laminated ME composites consisting of FeSiB (Metglas)/poly(vinylidene fluoride) (PVDF) is presented, whose zero-biased ME coupling characteristics and ME sensing performance have been investigated. The optimum size of composites have determined by optimizing the resonance magnetoelectric voltage coefficient, $\alpha $ ME,r, values. It is found that an appropriate size of composites is propitious to the zero-biased ME coupling characteristics due to the demagnetization effect. In addition, to evaluate the ability of composites to be used in bend status, the relationship between the resonant MEVC with $H_{dc}$ under different bend conditions have also been investigated, for which have never been or just partially discussed. As shown in Fig. 1, the zero-biased resonant MEVC showed an attenuation of approximately 76%, with increasing $\theta $ up to 50 °. Although the zero-biased resonant MEVC shows substantial decline under bend status, it still has very large value. Meanwhile, the proposed composites also have a commendable ac magnetic field $(H_{ac})$ sensing performance. The induced zero-biased ME voltage have an excellent linear relationship to ac magnetic field both at the low frequency (1kHz) and the resonant frequency (57.3kHz) as shown in Fig. 2. Obviously, it clearly indicated that the proposed zero-biased FeSiB/PVDF composite have great potential of being applied to wearable devices.