A new formalism for the paramagnetic spin susceptibility of metals using relativistic spin-polarised multiple-scattering theory: a temperature-dependent anisotropy effect

A new formalism for the static paramagnetic spin susceptibility of metals is given which includes a directional dependence on the magnetic response. This approach leads to an anisotropic generalized Stoner condition. We applied this theory to HCP and FCC cobalt. The starting point was the fully relativistic band structures and densities of states of both phases. The calculated susceptibilities show that an anisotropy appears in the HCP phase, but is absent for the FCC phase within this linear response theory. We also find a temperature dependence of this anisotropy. At low temperatures ( < 2500 K ) the easy axis is along the c axis whereas a t higher temperatures it lies in the ab plane.