The superconducting transition region in a Nb disk showing the paramagnetic
Meissner effect (PME) has been investigated in detail. From the field-cooled
magnetization behavior, two well-defined temperatures can be associated with
the appearance of the PME: T_1 (< T_c) indicates the characteristic temperature
where the paramagnetic moment first appears and a lower temperature T_p (< T_1)
defines the temperature where the positive moment no longer increases. During
the subsequent warming, the paramagnetic moment begins to decrease at T_p and
then vanishes at T_1 with the magnitude of the magnetization change between
these two temperatures being nearly the same as that during cooling. This
indicates that the nature of the PME is reversible and not associated with flux
motion. Furthermore, the appearance of this paramagnetic moment is even
observable in fields as large as 0.2 T even though the magnetization does not
remain positive to the lowest temperatures. Magnetic hysteresis loops in the
temperature range between T_1 and T_p also exhibit a distinct shape that is
different from the archetypal shape of a bulk type-II superconductor. These
behaviors are discussed in terms of the so-called 'giant vortex state'.Comment: Total 4 printed pages, 4 Figure