Temperature dependence of the spin-density asymmetry in Ni

Polarized neutron diffraction has been used to determine the temperature dependence of the asymmetry of the unpaired spin density in Ni. We find that 19% of the spin density has $e_g$ symmetry at 4.2 K; this increases continuously with increasing temperature and reaches about 26% $e_g$ at 634 K. Thus, the $e_g$ component of the ferromagnetic moment decreases less rapidly with increasing temperature than the $t_{2g}$ component. This suggests different temperature dependences for the spin splitting of the $t_{2g}$ and $e_g$ subbands.