The magneto-elastic response of a Terfenol-D (Tb.3Dy.7Fe1.92) ring has been experimentally investigated and analyzed. Ring structures give rise to complex behavior based on the interaction of the magnetic field with the material, which is further compounded with anisotropies associated with mechanical and magnetic properties. Discrete strain measurements were used to construct magnetostriction maps, which are used to elucidate the non-uniformity of the strain distribution due to geometrical factors and magnetic field interactions, namely, magnetic shielding and stable onion state in the ring structure.
The application domain of composite multiferroic materials with magnetoelectric coupling has been widening on the nano-, micro- and macro-scales. Generally, a composite multiferroic material consists of two, or more, layers of a piezoelectric material and a magnetostrictive material. In turn, the proliferation of multiferroics in more applications is accompanied by a keen focus on understanding the effect of material phases, geometry, bonding interface and arrangement of phases by performing theoretical, numerical and experimental studies to fundamentally elucidate the response. In this experimental study, a focus is given to exploit the effect of the polarization direction of the piezoelectric phase on the overall converse magnetoelectric (CME) response of a composite concentric PZT/Terfenol-D structure. Specifically, radially and axially polarized PZT rings were concentrically bonded to the outer surface of two Terfenol-D rings, respectively. It was found that the maximum, near resonance, CME coefficient of the axially-poled configuration is 443 mG V−1 when tested at 34 kHz, 80 kV m−1 electric field and 784 Oe bias magnetic field. On the other hand, the near resonance CME value for the radially-poled configuration remained nearly constant at 281.9 ± 5.3 mG V−1 between bias magnetic fields of 532 Oe and 1524 Oe at AC electric field of 80 kV m−1 with a frequency of 36 kHz. Interestingly, the CME coefficient of radially-poled composite structure exhibits a saturation behavior, while the CME coefficient for axially-poled structure is distinguished by a single peak. The difference in the response is attributed to the amount strain transduction due to the polarization direction.
A subclass of magnetoelectric composite multiferroics can bi-directionally couple AC electric fields with AC magnetic fields using mechanical strain as a mediator. Serendipitously, AC electric fields, AC magnetic fields, and vibrations, are the mediums used in capacitance-, induction-, and acoustic-based wireless energy transfer (WET), respectively. As a result, strainmediated composite multiferroics are uniquely positioned to transform all these modes of WET. This paper analytically and experimentally reports the ability of composite multiferroic hollow cylinders to wirelessly transfer energy to and from laminated multiferroic plates by the use of AC magnetic flux as an energy carrier. In all, the composite cylinders in conjunction with laminated plates are successfully demonstrated as a novel technology of bi-directional magnetoelectricbased WET. We report a peak extracted power of ∼100 μW, which is enough to wirelessly power a multitude of small electronic devices.
The effect of several mechanical boundary conditions on the dynamic magnetoelectric (ME) effect is analytically investigated for layered cylindrical composites. The study consists of deriving a mechanics-based model for two concentric cylinders made of lead-zirconate-titanate (PZT) and cobalt ferrite (CoFe 2 O 4 ), separated by a thin elastic layer, which is treated as strain mediator with no effect on the functional behavior of the system. Different thicknesses of the cylindrical composites and the elastic layer are considered in this study. For each case, nine sets of boundary conditions, four traditional and five non-traditional, were applied. Results show the dependence of the ME effect on the boundary conditions as well as on the inclusion of the elastic layer between the two cylinders, where both affect the strain transduction between the active layers; namely the piezomagnetic (CoFe 2 O 4 ) and piezoelectric (PZT) layers. It was found that the maximum ME effect is attained for conditions in which the outer boundary is subjected to a uniform mechanical pressure. The inclusion of a thin elastic bonding layer was found to increase the ME response, the thickness of which was further investigated to establish limits of applicability of the reported model.
A composite multiferroic ring was characterized under two orthogonal bias magnetic fields while electrically loaded near resonance to measure the circumferential converse magnetoelectric (CME) response. The composite multiferroic structure consisted of an inner magnetostrictive Terfenol-D ring with an axially aligned preferred magnetocrystalline axis bonded to a radially polarized outer piezoelectric poled lead zirconate titanate ring to form a concentric ring structure. A single uniform bias magnetic field was varied from zero to beyond magnetic saturation while the composite ring's axial alignment was changed from perpendicular to parallel with respect to the bias magnetic field direction. The change in the ring orientation thus subjected the ring to two orthogonal bias magnetic fields, whose strengths were calculated based on the orientation angle. The overall CME behavior was found to be largely correlated with the perpendicular magnetic field strength assisted with the shape anisotropy of the ring structure favoring magnetization along the longest axis. Nonetheless, the parallel magnetic field had a notable contribution to the CME response by enhancing the magnetization in the preferred axial direction and activating other unique magnetocrystalline axes. In all, the CME behavior with respect to two orthogonal bias magnetic fields is characterized by an interplay of magnetocrystalline and shape anisotropies bolstered by the parallel and perpendicular magnetic fields.
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