Competition between surface barriers and bulk pinning in a Nd2-xCexCuO4-y single crystal down to T/Tc=0.02

Isothermal dc magnetization measurements with the magnetic field applied parallel to the tetragonal c axis were made on an overdoped Nd2-xCexCuO4-y single crystal with a superconducting critical temperature T-c approximate to 19 K down to a reduced temperature T/T-c approximate to 0.02, an order of magnitude lower than values reported to date. The measurements revealed a pronounced "peak effect" anomaly in the irreversible part of the magnetization loop in which the magnetic field at which the peak occurs increases linearly with decreasing temperature down to T/T-c approximate to 0.05. The field when flux initially penetrates the sample increases exponentially as T-->0 due to surface barriers, obscuring the features of the peak anomaly at low temperatures. The irreversibility field follows a power law down to T/T-c approximate to 0.2 and deviates from the power law at low temperatures, again indicative of surface barriers.