  We study the phase structure of QCD with three degenerate flavors in the
external magnetic fields using highly improved staggered quarks (HISQ). The
simulations are performed on $16^3\times 6$ lattice. In order to investigate
the quark mass dependence of the chiral transition we choose the values of the
bare quark masses 0.015 and 0.0009375 in the lattice unit, corresponding to
$m_\pi=320$ MeV and 80 MeV in the continuum limit. We found no indication of a
first order phase transition in the current window of quark masses and external
magnetic fields. Unlike to the case with standard staggered fermions inverse
magnetic catalysis is always observed at about the critical temperature. The
microscopic origin of this phenomena are further discussed by looking into the
Dirac eigenvalue spectrum.
