Systems are provided for the efficient generation of oscillating magnetic fields below the Low Frequency band. These systems generate such fields by mechanically rotating one or more diametrically-magnetized permanent magnets. In order to reduce friction, the magnets are rotated by applying a motive magnetic field to the magnet(s) to rotate the magnet(s) and thereby generate the oscillating magnetic field. Additionally, diamagnetic repulsion, active magnetic field control, and/or biasing permanent magnets are employed to levitate the rotating magnet(s), further reducing friction and increasing system efficiency. These systems may be employed to generate modulated low-frequency oscillating magnetic fields for communication through seawater, rocks, or other obstacles. Additionally or alternatively, these systems may be employed to generate low-frequency oscillating magnetic fields for navigation and location sensing, resource identification and extraction, or other applications.