  We have employed the relativistic coupled cluster theory to calculate the
magnetic dipole and electric quadrupole hyperfine constants for the ground and
low lying excited states of singly ionized magnesium. Comparison with
experimental and the other theoretical results are done and predictions are
also made for a few low lying excited states which could be of interest. We
have made comparative studies of the important many body effects contributing
to the hyperfine constants for the different states of the ion.
