  Under an in-plane magnetic field, the density of states of quasi
two-dimensional carriers deviates from the occasionally stereotypic step-like
form both quantitatively and qualitatively. For the first time, we study how
this affects the spin-subband populations and the spin-polarization as
functions of the temperature, T, and the in-plane magnetic field, B, for narrow
to wide dilute-magnetic-semiconductor quantum wells. We examine a wide range of
material and structural parameters, focusing on the quantum well width, the
magnitude of the spin-spin exchange interaction, and the sheet carrier
concentration. Generally, increasing T, the carrier spin-splitting, U,
decreases, augmenting the influence of the minority-spin carriers. Increasing
B, U increases and accordingly carriers populate majority-spin subbands while
they abandon minority-spin subbands. Furthermore, in line with the density of
states modification, all energetically higher subbands become gradually
depopulated. We also indicate the ranges where the system is completely
spin-polarized.
