High‐Efficiency Magneto‐Mechanical Resonator for Enhanced ELF Magnetic Field Communication and Wireless Energy Transmission

Abstract The classical relation B = µH , integral to Maxwell's equations, has served as the foundation for passive magnetic field amplification for over a century. However, this linear magnetization paradigm faces limitations due to magnetic losses and demagnetization effects, particularly in high‐permeability ( µ ) materials. Here, a passive Magneto‐Mechanical Resonator (MMR) capable of amplifying and transmitting extremely low‐frequency (ELF) magnetic fields is reported with a gain exceeding 3000 through the oscillation of magnetic dipole moments, rather than traditional magnetization. Furthermore, an equivalent circuit model is built to reveal this swinging amplification mechanism. The MMR based devices support the diverse functionalities, including i) high‐efficiency ELF wireless energy transmission in seawater, overcoming the limitations of conventional resonant coils, ii) an ELF B‐field emitting antenna for cross‐medium communication with a quality factor (Q) over an order of magnitude higher than state‐of‐the‐art devices, and iii) passive, self‐sensing capabilities for detecting abnormal vibrations or magnetic signal. This passive, swinging oscillation amplification concept offers a novel approach for designing compact, energy‐efficient, and multifunctional devices for communication, energy transfer, and sensing at low frequencies.