  We report on the presence of weak links in the intermetallic superconductor
MgB2 from the non-resonant microwave absorption (NRMA) studies on the MgB2 thin
film. The strong low field signal, which is the characteristics of weak links
and the presence of hysteresis, which arises due to flux trapping, are
observed. The studies are carried out as a function of temperature, microwave
power, magnitude of modulation field and the range of field scan. Presence of
weak links is discussed in terms of increase in the oxygen content of grain
boundaries in the thin film and because of disorder effects arises due to the
aging of the sample. The pinning of flux lines with the changes in sweeping
direction leads to hysteresis in the NRMA signal and shows the contribution of
flux line motion in the power absorption.
