Analog of the Procopiu Effect in Type II Superconducting Wires Carrying an Alternating Current

Abstract

The longitudinal magnetization of a ferromagnetic wire which carries an alternating current in the presence of a stationary longitudinal magnetic field varies at twice the frequency of the applied current. This effect discovered by Procopiu has recently been studied by Skórski and Duracz. An analogous effect is observed when the ferromagnetic wire is replaced by a wire of a nonideal type II superconductor and the current alternates below the critical value I_c. In the superconducting case, the longitudinal magnetization of the wire may oscillate from strongly paramagnetic to strongly diamagnetic as the conduction current is varied. The frequency of oscillation of the magnetization is twice that of the applied current as in the ferromagnetic case. With the current varying as I=I_c cos ωt the longitudinal magnetization can be described by M_z≈A+B cos (2ωt), where A and B are temperature‐ and field‐dependent parameters. This phenomenon in the superconducting state is shown to arise from helical patterns of induced and conduction current flow in the presence of a longitudinal field.