Evolution of the magnetic-field profile in Tl2Ba2CuO6: Consequences for the second magnetization peak

Using an array of mu m-sized Hall probes to measure local magnetic-field gr adients, we have investigated magnetization hysteresis loops in single-crys tal Tl2Ba2CuO6. Our technique allows us to delineate bulk and surface contr ibutions to the field profiles across the sample. In particular, we are abl e to identify the component in the field gradient responsible for the "seco nd peak" in the magnetization loop. We find that this particular component decays with a field-independent relaxation rate, suggesting a static origin of the second peak. [S0163-1829(99)00225-8].