Magnetic levitation by rotation

A permanent magnet can be levitated simply by placing it in the vicinity of another permanent magnet that rotates in the order of 200 Hz. This surprising effect can be easily reproduced in the laboratory with off-the-shelf components. Here, we have investigated this novel type of magnetic levitation experimentally and clarified the underlying physics. Using a 19-mm-diameter spherical Nd-Fe-B magnet as the rotor magnet, we have captured the detailed motion of levitating spherical Nd -Fe -B magnets, denoted floater magnets, as well as the influence of the rotation speed and magnet size on the levitation. We have found that as levitation occurs, the floater-magnet frequency locks with the rotor magnet and, noticeably, that the magnetization of the floater is oriented close to the axis of rotation and toward the like pole of the rotor magnet. This is in contrast to what might be expected by the laws of magnetostatics, as the floater is observed to align its magnetization essentially perpendicular to the magnetic field of the rotor. Moreover, we have found that the size of the floater has a clear influence on the levitation: the smaller the floater, the higher the rotor speed that is necessary to achieve levitation and the further away the levitation point shifts. Despite the unexpected magnetic configuration during levitation, we have verified that magnetostatic interactions between the rotating magnets are responsible for creating the equilibrium position of the floater. Hence, this type of magnetic levitation does not rely on gravity as a balancing force to achieve an equilibrium position. Based on theoretical arguments and a numerical model, we show that a constant vertical field and eddy-current-enhanced damping are sufficient to produce levitation from rest. This enables a gyroscopically stabilized counterintuitive steady-state moment orientation and the resulting magnetostatically stable midair equilibrium point. The numerical model displays the same trends with respect to the rotation speed and the floater-magnet size as seen in the experiments.