Double and Triple Peaks in the a.c. Losses of Some Superconductors

Abstract

We measure transverse a.c. losses of "dirty", fully oxygenated untwinned YBa2Cu3O7-δ single crystals and 2H-NbSe2 single crystals using a low-frequency pendulum oscillator. The data constitute evidence for a peak effect of the critical current as a function of the temperature in these compounds. The existence of the peak effect explains some complex peak structures in the losses observed in "dirty" samples of moderately anisotropic three-dimensional superconductors.