Doping dependence of vortex regimes in Y1−xPrxBa2Cu3O7− single crystals

Magnetic relaxation measurements on a series of Y1−xPrxBa2Cu3O7− x=0.13, 0.34, and 0.47 single crystals were performed over a large field and temperature range in order to investigate the characteristics of the vortex matter across the second magnetization peak SMP . The magnitude of the SMP varies nonmonotonically with Pr concentration, i.e., the irreversible magnetization normalized by its value at the onset field Hon displays a maximum for the x=0.34 single crystal. The two characteristic fields, Hon and Hsp, follow different temperature T dependences: Hon T on and Hsp 1− T /Tc 2 sp. The extracted values of the apparent activation energy U* and the creep exponent display a maximum at a field Hon H* Hsp. Their field dependences point toward the coexistence of both elastic and plastic creep for H Hon. The degree of participation of each creep mechanism is determined by the charge carrier density, which controls both the elastic properties of the vortex matter and the pinning potential.