Polarized isomers of Na clusters and anomalous magnetic response

Spontaneously spin-polarized states of ${\mathrm{Na}}_{12}$ and ${\mathrm{Na}}_{16}$ are investigated using a spin-density-functional description of the valence electrons and local pseudopotentials for their coupling to the ionic cores. We find that both systems have low-lying polarized isomers. An anomalous temperature dependence of the magnetic response in terms of a magnetic susceptibility rising with temperature is the practical consequence of this spin isomerism.