Given the fact that electrons are fermions, for each state available in the Landau levels it corresponds to two electrons, one electron with each value for the spin s = ± ± 1 2 . However, if a large magnetic field is applied, the energies split into two levels due to the magnetic moment associated with the alignment of the spin with the magnetic field. The difference in the energies is Δ Δ E = ± ± 1 2 g μ μ B B being g a factor which depends on the material ( g = 2 for free electrons) and μ μ B the Bohr magneton. The sign + is taken when the spin is parallel to the field and − − when it is antiparallel. This fact called spin splitting implies that the density of states for each level is reduced by a half. Note that Δ Δ E is proportional to the magnetic field so, the larger the magnetic field is, the more relevant is the split.