The possibility of tuning the magnetic properties of materials with voltage (converse magnetoelectricity) or generating electric voltage with magnetic fields (direct magnetoelectricity) has opened new avenues in a large variety of technological fields, ranging from information technologies to healthcare devices and including a great number of multifunctional integrated systems, such as mechanical antennas, magnetometers, and radio frequency (RF) tunable inductors, which have been realized due to the strong strain-mediated magnetoelectric (ME) coupling found in ME composites. The development of single-phase multiferroic materials (which exhibit simultaneous ferroelectric and ferromagnetic or antiferromagnetic orders), multiferroic heterostructures, as well as progress in other ME mechanisms, such as electrostatic surface charging or magneto-ionics (voltage-driven ion migration), have a large potential to boost energy efficiency in spintronics and magnetic actuators. This article focuses on existing ME materials and devices and reviews the state of the art in their performance. The most recent progress on different ME devices based on ME heterostructures is presented but with a larger emphasis on ME antennas and sensors due to the significant advances achieved in these applications. The rapid development of mechanically actuated ME antennas has been observed over the past several years, producing ME antennas that are miniaturized by 1-2 orders compared to conventional antenna size. Magnetic sensors based on simple ME composites are potentially promising alternatives to conventional magnetometers due to their very good detectivity (<; pT/Hz ^1/2 ) at low frequencies. Other ME devices reviewed in this article include RF tunable inductors with high inductance tunability and quality (Q) factor; non-reciprocal microelectromechanical system (MEMS) bandpass filters with dual H- and E-field tunability; passive isolators and gyrators in the low-frequency (LF) range; and ME random access memories for low-power data storage. All these compact and lightweight ME devices are also promising for future biomedical and wireless applications. Finally, some open questions and future directions where the community might be headed are provided.

Surface acoustic wave magnetic field sensors based on guided Love waves using the ΔE effect of a magnetostrictive thin film have been shown to be promising candidates for the measurement of weak fields at low frequencies as required for biomagnetic applications or as current sensors benefitting from the large dynamic range and bandwidth. The deposition of soft magnetic films with high magnetostriction is, however, more challenging on piezoelectric substrates such as quartz than on silicon. Thermally induced anisotropic expansion during the deposition process or during post-deposition magnetic field annealing leads to uniaxial stresses acting on the films, which makes the precise control of magnetic anisotropy difficult. Accordingly, this work analyzes the influence of the deposition process and heat treatment on the performance of Love wave devices. ST-cut quartz based delay line surface acoustic wave sensors with a SiO₂ guiding layer are employed, and a 200 nm layer of amorphous magnetostrictive (Fe₉₀Co₁₀)₇₈Si₁₂B₁₀ is used as the sensitive element. Magneto-optical imaging is performed for magnetic domain characterization, and the sensor performance is characterized in terms of bias field dependent phase sensitivity and frequency dependent phase noise. By performing a low temperature deposition in an external magnetic field, considerable improvement in limits of detection at biomagnetic relevant frequencies down to 70 $\mathrm{pT}/\sqrt{\text{Hz}}$ at 10 Hz and 25 $\mathrm{pT}/\sqrt{\text{Hz}}$ at 100 Hz is achieved.

In this work, the first surface acoustic-wave-based magnetic field sensor using thin-film AlScN as piezoelectric material deposited on a silicon substrate is presented. The fabrication is based on standard semiconductor technology. The acoustically active area consists of an AlScN layer that can be excited with interdigital transducers, a smoothing SiO₂ layer, and a magnetostrictive FeCoSiB film. The detection limit of this sensor is 2.4 nT/$\sqrt{\mathrm{Hz}}$ at 10 Hz and 72 pT/$\sqrt{\mathrm{Hz}}$ at 10 kHz at an input power of 20 dBm. The dynamic range was found to span from about $\pm$1.7 mT to the corresponding limit of detection, leading to an interval of about 8 orders of magnitude. Fabrication, achieved sensitivity, and noise floor of the sensors are presented.

Surface acoustic wave (SAW) sensors for the detection of magnetic fields are currently being studied scientifically in many ways, especially since both their sensitivity as well as their detectivity could be significantly improved by the utilization of shear horizontal surface acoustic waves, i.e., Love waves, instead of Rayleigh waves. By now, low-frequency limits of detection (LOD) below 100 pT/$\sqrt{\mathrm{Hz}}$ can be achieved. However, the LOD can only be further improved by gaining a deep understanding of the existing sensor-intrinsic noise sources and their impact on the sensor’s overall performance. This paper reports on a comprehensive study of the inherent noise of SAW delay line magnetic field sensors. In addition to the noise, however, the sensitivity is of importance, since both quantities are equally important for the LOD. Following the necessary explanations of the electrical and magnetic sensor properties, a further focus is on the losses within the sensor, since these are closely linked to the noise. The considered parameters are in particular the ambient magnetic bias field and the input power of the sensor. Depending on the sensor’s operating point, various noise mechanisms contribute to $f^0$ white phase noise, $f^{-1}$ flicker phase noise, and $f^{-2}$ random walk of phase. Flicker phase noise due to magnetic hysteresis losses, i.e. random fluctuations of the magnetization, is usually dominant under typical operating conditions. Noise characteristics are related to the overall magnetic and magnetic domain behavior. Both calculations and measurements show that the LOD cannot be further improved by increasing the sensitivity. Instead, the losses occurring in the magnetic material need to be decreased.

We report the first study of diverse ferromagnetic thin films via acoustically driven ferromagnetic resonance (ADFMR). Angle- and field-dependent ADFMR was performed at room temperature on thin-films of FeCo, FeCoGd, FeGaB, and FeCoSiB, which take the place of the ferromagnetic Ni film traditionally used in these experiments, with a few exceptions. Surface acoustic wave (SAW) devices are operated at three harmonics in the 0.8-2 GHz frequency range. Each magnetic material has a unique ADFMR signature: FeCo shows a standard four-lobe pattern with a broad ∼100-mT linewidth; FeCoGd breaks odd symmetry and reveals an additional lowfield lobe; and FeGaB and FeCoSiB show extreme asymmetry and narrow linewidths. In FeCoSiB we observe nonreciprocal SAW propagation. We also perform direct comparison of ADFMR and standard ferromagnetic resonance (FMR) on the same devices, revealing that ADFMR absorption is measurable even when FMR signals are extremely weak, and magnetic anisotropy does not fully explain asymmetry observed in ADFMR. These results demonstrate that strain-driven magnetization dynamics is a rich field; the effects can be observed in a variety of materials with unexpected behavior, motivating further work in the field.