  We have studied the nature and dynamics of spin-dependent charge carrier
recombination in Tris(8-hydroxyquinolinato) aluminum (Alq$_3$) films in light
emitting diodes at room temperature using continuous wave and pulsed
electrically detected magnetic resonance (EDMR) spectroscopy. We found that the
EDMR signal is dominated by an electron-hole recombination process, and
another, weaker EDMR signal whose fundamental nature was investigated. From the
pulsed EDMR measurements we obtained a carrier spin relaxation time, $T_2 =
45\pm 25$ ns which is much shorter than $T_2$ in conjugated polymers, but
relatively long for a molecule containing elements with high atomic number.
Using multi-frequency continuous wave EDMR spectroscopy, we obtained the local
hyperfine field distributions for electrons and holes, as well as their
respective spin-orbit coupling induced g-factor and g-strain values.
