  The magnetic moments of ${}^2{H}$, ${}^3{He}$ and ${}^3{H}$ as well as the
thermal neutron capture rate on the proton are calculated using heavy baryon
chiral perturbation theory {\it \`{a} la} Weinberg. The M1 operators have been
derived up to {N$^3$LO}. The nuclear matrix elements are evaluated with the use
of wave functions obtained by carrying out variational Monte Carlo calculations
for a realistic nuclear Hamiltonian involving high-precision phenomenological
potentials like Argonne Av18 and Urbana IX tri-nucleon interactions. We discuss
the potential- and cutoff-dependence of the results.
