The dashed line in Fig. corresponds to the number of unpaired electrons per unit cell and therefore the maximum spin density. From this, it is clear the spin density is equal to the number of unpaired Nb electrons for the half-metallic phase. This is due to the presence of only spin up states close to the Fermi level which leads to a theoretical 100% spin polarisation. However, as the splitting between the spin states decreases and the phase becomes metallic there are also spin down states at the Fermi level (Fig. ). This results in a deviation from the ideal 100% spin polarisation, eventually resulting in a loss of magnetic ordering around x = 0.14.