  This paper presents a new method for generating low-frequency electromagnetic
waves for navigation and communication in challenging environments, such as
underwater and underground. The main idea is to store magnetic energy in two
different spaces using the interaction between a permanent magnet and a
magnetic material. The magnetic reluctance of the medium around the permanent
magnet is modulated to change the magnetic flux path. The nonlinear properties
of magnetic material as a critical phenomenon are used for effective
modulation. As a result, a time-variant field is generated by the modulation of
the permanent magnet flux. This non-resonant time-variant characterization
means that the transmitter is not bound to the fundamental limits of the
antennas and can transmit higher data rates. A prototype transmitter as a
prove-of-concept is designed and tested based on the proposed idea. Compared to
the rotating magnet, the prototyped transmitter can modulate $50\%$ of the
stored energy of the permanent magnet with much lower power consumption.
