Magnetoelastic theory of type-II superconductors in the mixed state.

Abstract

This paper presents a macroscopic theory for analyzing the magnetoelastic response of elastic type-II superconductors in the mixed state. The theory includes not only the vortex-dynamic effect, the normal-current effect, and the flux-flow Hall effect, but also the effect of the London moment induced by the local motion of the deformable superconductor in the mixed state. The theory is considered to be valid within the framework of the generalized Galilean relativity at the magnetoquasistatic approximation. By this theory, a set of linearized coupled wave equations is derived to study some problems concerning magnetoelastic wave propagation in type-II superconductors in the mixed state. Attenuation and dispersion behaviors of the magnetoelastic wave are then analyzed. It is shown that the nonlocal effect on the length scale of the London penetration depth may be of importance in analyzing the propagation behavior of the magnetoelastic wave at frequencies higher than the depinning frequency. It is also shown that the effect of the London moment induced by dynamic deformation can be of significance as compared with the effect of the normal Lorentz current on the magnetoelastic coupling behavior of elastic type-II superconductors in the mixed state. Furthermore, it is found that there is a phase change between the transverse elastic wave and the magnetic wave induced in the type-II superconductor in the mixed state. This effect is found to be closely related to the vortex-dynamic properties of the superconductor.