Magnetoelectric (ME) cantilever resonators have been successfully employed as magnetic sensors to measure low magnetic fields; however, high relative resolution enabling magnetometry in high magnetic fields is lacking. Here, we present on-chip silicon based ME microelectromechanical (MEMS) doubly clamped resonators which can be utilized as high sensitivity, low power magnetic sensors. The resonator is a fully suspended thin film ME heterostructure composed of an active magnetoelastic layer (Fe_0.3Co_0.7), which is strain coupled to a piezoelectric signal/excitation layer (AlN). By controlling uniaxial stress arising from the large magnetoelastic properties of magnetostrictive FeCo, a magnetically driven shift of the resonance frequency of the first fundamental flexural mode is observed. The theoretical intrinsic magnetic noise floor of such sensors reaches a minimum value of 35 $pT/\sqrt{Hz}$ . This approach shows a magnetic field sensitivity of ∼5 Hz/mT in a bias magnetic field of up to 120 mT. Such sensors have the potential in applications required for enhanced dynamic sensitivity in high-field magnetometry.

Magnetoelectric composites have shown promise in low power magnetic field sensing with responsive detection of low frequency fields through the modulation of electromechanical resonance by exploiting a nonlinearity in magnetoelastic properties (ΔE effect). There is also the as-of-yet unrealized potential of tuning this effect to further enhance the shift in resonant frequency of these devices. In the present work, the magnetic field sensitivity was modulated in a bending mode stress reconfigurable sensor through the application of uniaxial tensile stress, reaching up to 8% f₀/mT. The minimum magnetic noise floor was determined by detecting the frequency shift using a phase locked loop circuit and was found to directly correspond to the maximum in magnetic field sensitivity that resulted from the ΔE effect.

Electrical switching of ferroelectric domains and subsequent domain wall motion promotes strong piezoelectric activity, however, light scatters at refractive index discontinuities such as those found at domain wall boundaries. Thus, simultaneously achieving large piezoelectric effect and high optical transmissivity is generally deemed infeasible. Here, it is demonstrated that the ferroelectric domains in perovskite Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ domain‐engineered crystals can be manipulated by electrical field and mechanical stress to reversibly and repeatably, with small hysteresis, transform the opaque polydomain structure into a highly transparent monodomain state. This control of optical properties can be achieved at very low electric fields (less than 1.5 kV cm⁻¹) and is accompanied by a large (>10 000 pm V⁻¹) piezoelectric coefficient that is superior to linear state‐of‐the‐art materials by a factor of three or more. The coexistence of tunable optical transmissivity and high piezoelectricity paves the way for a new class of photonic devices.

Combining and coupling both magnetic and electric properties in one single phase multiferroic material has attracted high interest recently to enable a broad range of novel devices and applications. To evaluate one potential route toward new multiferroics, we have studied 0.5% Fe-doped BaTiO₃ single crystals and measured the ferroelectric, magnetic, and multiferroic properties. X-ray absorption spectroscopy shows the presence of Fe³⁺, and magnetic measurements confirmed that this has a significant impact on the magnetic properties. Doping of iron introduces paramagnetism from lone iron atoms as well as what appears to be a weak ferromagnetism. Multiferroicity and magnetoelectric (ME) coupling were observed in the polarization-electric field hysteresis loops with an applied magnetic field, yet there was no direct evidence that ME coupling persists when the sample was in the defect dipole-aligned state.

Low noise sensors with low power consumption are needed for sensing the bio-magnetic potentials produced by the human body. Compared to their electrical counterparts, bio-magnetic sensors are non-invasive and non-contact. A strain modulated FeCo-Hf/AlScN based sensor with a bandwidth of 3.4 kHz and a magnetic noise spectral density at 1 kHz of 59.5 pT/√Hz before demodulation and 98.5 pT/√Hz after demodulation in an unshielded environment is presented. The footprint of the sensor including flux concentrators is 0.125 cm ² , and the total power consumption of the printed circuit board based readout electronics is 440 mW. A theoretical analysis for scaling of the sensitivity and the noise spectral density of modulated multiferroic sensor systems is presented.

Recent advances in phase transition transduction enabled the design of a non-resonant broadband mechanical energy harvester that is capable of delivering an energy density per cycle up to two orders of magnitude larger than resonant cantilever piezoelectric type generators. This was achieved in a [011] oriented and poled domain engineered relaxor ferroelectric single crystal, mechanically biased to a state just below the ferroelectric rhombohedral (F_R)-ferroelectric orthorhombic (F_O) phase transformation. Therefore, a small variation in an input parameter, e.g., electrical, mechanical, or thermal will generate a large output due to the significant polarization change associated with the transition. This idea was extended in the present work to design a non-resonant, multi-domain magnetoelectric composite hybrid harvester comprised of highly magnetostrictive alloy, [Fe_81.4Ga_18.6 (Galfenol) or Tb_xDy_1-xFe₂ (Terfenol-D)], and lead indium niobate–lead magnesium niobate–lead titanate (PIN-PMN-PT) domain engineered relaxor ferroelectric single crystal. A small magnetic field applied to the coupled device causes the magnetostrictive element to expand, and the resulting stress forces the phase change in the relaxor ferroelectric single crystal. We have demonstrated high energy conversion in this magnetoelectric device by triggering the F_R-F_O transition in the single crystal by a small ac magnetic field in a broad frequency range that is important for multi-domain hybrid energy harvesting devices.