  Piezolever torque magnetometry has been used to measure the magnetization of
superconducting Tl2Ba2CuO6. Three crystals with different levels of oxygen
overdoping were investigated in magnetic fields up to 10 Tesla. In all cases,
the magnetization above the irreversibility line was found to depart from the
behaviour M ~ ln(Hc2/H) of a simple London-like vortex liquid. In particular,
for a strongly overdoped (Tc = 15K) crystal, the remnant superconducting order
above the irreversibility line is characterized by a linear diamagnetic
response (M ~ H) that persists well above Tc and also up to the highest field
employed.
