Oscillation stability of levitated HTSC in inhomogeneous magnetic field

The stability of the horizontal and vertical oscillations of anisotropic high-T-c superconductors (HTSC's) in an inhomogeneous magnetic field has been investigated. The oscillation amplitude of the levitated HTSC's was measured as function of the external force frequency and amplitude. The resonant oscillations of the levitated superconductors were observed for external field frequencies from 20 to 40 Hz. It is demonstrated that the system consisting of a superconductor, a coil and four permanent magnets has strong stiffness. This behavior is described with the general theory of oscillations.