Low frequency (LF) dual-driven magnetoelectric (i.e., DDME) antennas are proposed, which include a pair of self-biased magnetoelectric heterostructures (i.e., Ni/Metglas/ [Pb(Zr,Ti)O₃]₅/Metglas/Ni) wrapped with small coils. For the DDME transmitter, the [Pb(Zr,Ti)O₃]₅ layers are designed as a piezoelectric transformer. This enhances the transmitted magnetic field significantly due to the dual-driven mode: the generated magnetic field of transmitting coils driven by the transformer at the magneto-mechanical resonance and magnetization oscillation of magnetostrictive layer driven by the mechanical stress of inverse piezoelectric effect. Meanwhile, the DDME receiver consists of a self-biased magnetoelectric heterostructure wrapped with search coils, whose SNR is improved due to the synergistically induced voltage of Faraday law's induction and magnetoelectric effects. The nonmonotonic inductance of search coils near MMR broadens the bandwidth (1904kHz) due to the LC resonances at multiple frequencies. The study indicates that the DDME antenna achieves a communication distance of 11m with power consumption of 212.7mW, whose operation distance and channel capacity (12.54kbit/s) are 1.69 times and 10.62 times larger than that of ME antenna (i.e., Ni/Metglas/[Pb(Zr,Ti)O₃]₅ /Metglas/Ni). The communication distance can be further increased to 170 m with a larger DDME antenna. Furthermore, the DDME antenna can realize more robust ASK modulation compared to ME antenna.

It is an important engineering challenge to detect a weak magnetic field ${H}_{AC}$ at low frequencies (1-100 Hz) due to large noise. In this work, a magnetoelectric (ME) sensor using single-crystal quartz material as the piezoelectric phase and optimized magnetostrictive layers has been presented to sense the low-frequency magnetic field signals. Firstly, the ME response properties of the bulk Metglas/quartz/Metglas laminate sensor were studied and a high ME coefficient of 3038 V/(cm $\cdot $ Oe) has been attained in its electromechanical resonance frequency. With frequency modulation technique, which a magnetic low-frequency signal can be transferred to around resonance frequency of the sensor, the proposed sensor was used to detect the low frequency magnetic field signals under zero bias conditions. It is experimentally found that the absolute resolution with respect to a 1 Hz magnetic field can be decreased as low as 44 pT ± 1.41 pT with 20 layers of Metglas. More importantly, the ME coefficients with different layers under zero bias and the effect of Metglas layers on the limit of the detection at 1 Hz also have been investigated. The results show that the limit of the detection at 1 Hz can be decreased to 10 pT ± 0.32 pT with 14 layers of Metglas which indicates an enhancement by 4.4 times in comparison with 20 layers. This simple bulk Metglas/quartz/Metglas laminate sensor with optimized layers has a great potential to be used for low-frequency bio-magnetic signals measurement at room temperature.

Recently acoustically driven magnetoelectric (ME) antennas provide a promising candidate for portable low frequencies (LF 30-300 kHz) transceivers in the high-loss medium. However, single ME antenna constraints the transmitted magnetic field due to the weak magnetic moment and low strain modulated magnetization efficiency. Hence a multi-physical field driven magnetoelectric antenna array consisting of double elastic plates sandwiched between multiple arranged PZT8/Metglas/Ni laminates is proposed, which can enhance the transmitted magnetic field nonlinearly with increased antennas. Here the accumulated AC strain and magnetic field of multiple antennas intensify with increased antennas and couple in a positive feedback way. Specifically, the AC piezostrain of adjacent antennas couples through the elastic plate along the length direction, enhancing the modulation of neighboring antennas’ magnetization oscillations; meanwhile, the enhanced magnetic coupling among adjacent antennas along the width direction produces additional magnetostrictive strains, which enhance the Q values of converse magnetoelectric effect and effective strains propagated in the elastic plate, thereby further improving the transmitted magnetic field. First, an equivalent circuit model based on magnetic and strain modulated motion equations is proposed to understand and optimize the ME antenna array. Furthermore, due to the multi-physical field driven effect of fabricated antenna array, the 3 × 3 array can enhance the transmitted magnetic field to 19.8 times compared to that of a single antenna. Such nonlinear improvements can further reach 1337 times for the 10 × 10 antenna array. This provides a power-efficient method to enhance the magnetic field transmission efficiency at low frequency.

Heat-assisted interlaced magnetic recording (HIMR) with interlaced track layout architecture enables the further increased areal density compared to the conventional heat-assisted magnetic recording. However, the severe transition curvatures of low temperature written tracks cause noticeable nonlinear distortions of readback signal, and the 2-D intersymbol interference (ISI), media noise, and thermal jitter also bring the challenges for data recovery. Correspondingly, a multitrack detection scheme with 2-D iterative soft estimate aided neural network equalizer (2D-ISA NNE) is proposed for the HIMR system, which iteratively feeds back the soft estimate of reliable sidetracks’ information (e.g., high temperature written tracks) during the neural network equalization (NNE) of middle track (e.g., low temperature written track). Here, the Bahl–Cocke–Jelinek–Raviv (BCJR) detector and low-density parity-check (LDPC) decoder are utilized for the following data detection and error corrections. Then, the similar ISA NNE is implemented to recover the sidetracks’ data. It is found that the proposed 2D-ISA NNE algorithm mitigates the 2-D ISI and nonlinear distortion more effectively compared to the conventional 2-D linear equalizer (LE) and neural network equalizer (NNE). For HIMR at the channel bit density of 3.51 Tb/in ² and overlapping ratio of 0.46, the proposed 2D-ISA NNE algorithm significantly decreases the bit error rate gap between the low temperature and high temperature written tracks. For the low temperature written track, it provides 3.1 and 4 dB signal-to-noise ratio (SNR) gains compared to the conventional 2-D NNE and 2-D LE, respectively.

To improve the dc magnetic field sensitivity of conventional inductor-type (i.e., longitudinally driven giant magnetoimpedance) sensor at the low excitation frequency, a transformer-type laminated magnetic sensor consisting of soft magnetostrictive alloy FeBSiC/piezoelectric ceramics Pb(Zr,Ti)O ₃ /FeBSiC heterostructure wrapped with both the exciting and sensing coils (i.e., FPFC _ex C _se ) is proposed. Compared to the inductor-type dc magnetic sensor (i.e., H _ac driven FeBSiC ribbons with only exciting coils), on one hand the ac magnetic field (H _ac ) produced by the exciting coil and the stress produced by electrically driven PZT are synchronously coupled to enhance the magnetic induction variation of FeBSiC and the induced voltage sensitivity of sensing coils. On the other hand the mutual inductance induced voltage eliminates the weak skin effect at the low excitation frequency. When the exciting coil and PZT of FPFC _ex C _se laminate are synchronously excited with 5 mA ac current and 5 V voltage at the mechanical resonance frequency, the maximum magnetic field sensitivity of 21200 V/T is achieved. This is about 4.08 times and 2.98 times as high as that of FeBSiC ribbon with only exciting coils (5190 V/T) and FeBSiC ribbons with both exciting and sensing coils (7120 V/T), respectively. Furthermore the equivalent magnetic noise of $114~{\mathrm {pT}}/\sqrt {{\mathrm {Hz}}} $ (at 1Hz) is achieved by the FPFC _ex C _se laminate, which is obviously lower than that of H _ac driven FeBSiC ribbons.