Micromagnetic Theory of Time-Dependent Suprastriction

A micro magnetic theory is described for the treatment of suprastriction in a disc of a type-II superconductor with a timeoscillating external magnetic field perpendicular to the disc plane. By the action of the field vortices are driven out of the disc and reappear in the disc in a periodic manner, leading to a time and position-dependent magnetization M (r, t). This magnetization is calculated by the time-dependent GinzburgLandau equation of motion for the vortices. Thereby effects of the pinning of vortices at defects or of the intrinsic pinning of vortices in high-Tc superconductors with very short correlation lengths can be included. The magneto elastic interaction between the magnetization M (r, t) and the lattice generates magnetostrictive strains, which in the case of superconductors are called suprastrictive strains. They are calculated in the present paper.